# News for Octave Version 1

## Summary of changes for version 1.1.1

      * New built-in variables, default_return_value and
        define_all_return_values.

        If define_all_return_values is set to "false", Octave does not do
        anything special for return values that are left undefined, and
        you will get an error message if you try to use them.  For
        example, if the function

          function [x, y] = f ()
            y = 1;
          endfunction

        is called as

          octave:13> [a, b] = f ()

        Octave will print an error message for the attempt to assign an
        undefined value to `a'.

        This is incompatible with Matlab, which will define the return
        variable `x' to be the empty matrix.  To get the Matlab-like
        behavior, you can set the variable define_all_return_values to
        "true" (the default is "false") and default_return_value to `[]'
        (the default).  Then, any return values that remain undefined when
        the function returns will be initialized to `[]'.

        If the function is called without explicitly asking for an output,
        it will succeed.  This behavior is compatible and unchanged from
        previous versions of Octave.

      * New built-in variable suppress_verbose_help_message.  If set to
        "true", Octave will not add additional help information to the end
        of the output from the help command and usage messages for
        built-in commands.  The default value is "false".

      * New built-in variable PS4 is used as the prefix of echoed input
        (enabled with the --echo-input (-x) option).

      * The function size() now accepts an optional second argument.

      * Output from `save - ...' now goes through the pager.

      * The break statement may also be used to exit a function, for
        compatibility with Matlab.

      * The directory tree for installing Octave is now closer to
        conforming with the current GNU standards.

      * More bug fixes.

## Summary of changes for version 1.1.0

      * Octave now requires g++ 2.6.3 or later.  This change is necessary
        to make template instantiations cleaner, and to avoid having to
        have special cases in the code for earlier versions of gcc.

      * A new data structure type has been added.  The implementation uses
        an associative array with indices limited to strings, but the
        syntax is more like C-style structures.  here are some examples of
        using it.

        Elements of structures can be of any type, including structures:

          octave:1> x.a = 1;
          octave:2> x.b = [1, 2; 3, 4];
          octave:3> x.c = "string";
          octave:4> x
          x =

          octave:5> x.a
          x.a = 1
          octave:6> x.b
          x.b =

            1  2
            3  4

          octave:7> x.c
          x.c = string
          octave:8> x.b.d = 3
          x.b.d = 3
          octave:9> x.b
          x.b =

          octave:10> x.b.d
          x.b.d = 3

        Functions can return structures:

          octave:1> a = rand (3) + rand (3) * I;
          octave:2> function y = f (x)
          > y.re = real (x);
          > y.im = imag (x);
          > endfunction
          octave:3> f (a)
          ans =

          octave:4> ans.im
          ans.im =

            0.093411  0.229690  0.627585
            0.415128  0.221706  0.850341
            0.894990  0.343265  0.384018

          octave:5> ans.re
          ans.re =

            0.56234  0.14797  0.26416
            0.72120  0.62691  0.20910
            0.89211  0.25175  0.21081

        Return lists can include structure elements:

          octave:1> [x.u, x.s, x.v] = svd ([1, 2; 3, 4])
          x.u =

            -0.40455  -0.91451
            -0.91451   0.40455

          x.s =

            5.46499  0.00000
            0.00000  0.36597

          x.v =

            -0.57605   0.81742
            -0.81742  -0.57605

          octave:8> x
          x =

        This feature should be considered experimental, but it seems to
        work ok.  Suggestions for ways to improve it are welcome.

      * Octave now supports a limited form of exception handling modelled
        after the unwind-protect form of Lisp:

          unwind_protect
            BODY
          unwind_protect_cleanup
            CLEANUP
          end_unwind_protect

        Where BODY and CLEANUP are both optional and may contain any
        Octave expressions or commands.  The statements in CLEANUP are
        guaranteed to be executed regardless of how control exits BODY.

        This is useful to protect temporary changes to global variables
        from possible errors.  For example, the following code will always
        restore the original value of the built-in variable
        do_fortran_indexing even if an error occurs while performing the
        indexing operation.

          save_do_fortran_indexing = do_fortran_indexing;
          unwind_protect
            do_fortran_indexing = "true";
            elt = a (idx)
          unwind_protect_cleanup
            do_fortran_indexing = save_do_fortran_indexing;
          end_unwind_protect

        Without unwind_protect, the value of do_fortran_indexing would not
        be restored if an error occurs while performing the indexing
        operation because evaluation would stop at the point of the error
        and the statement to restore the value would not be executed.

      * Recursive directory searching has been implemented using Karl
        Berry's kpathsea library.  Directories below path elements that
        end in // are searched recursively for .m files.

      * Octave now waits for additional input when a pair of parentheses
        is `open' instead of giving an error.  This allows one to write
        statements like this

          if (big_long_variable_name == other_long_variable_name
              || not_so_short_variable_name > 4
              && y > x)
            some (code, here);

        without having to clutter up the if statement with continuation
        characters.

      * Continuation lines are now allowed in string constants and are
        handled correctly inside matrix constants.

      * Both `...{whitespace}\n' and `\{whitespace}\n' can be used to
        introduce continuation lines, where {whitespace} may include
        spaces, tabs and comemnts.

      * The script directory has been split up by topic.

      * Dynamic linking mostly works with dld.  The following limitations
        are known problems:

        -- Clearing dynamically linked functions doesn't work.

        -- Dynamic linking only works with dld, which has not been ported
           to very many systems yet.

        -- Configuring with --enable-lite-kernel seems to mostly work to
           make nonessential built-in functions dynamically loaded, but
           there also seem to be some problems.  For example, fsolve seems
           to always return info == 3.  This is difficult to debug since
           gdb won't seem to allow breakpoints to be set inside
           dynamically loaded functions.

        -- Octave uses a lot of memory if the dynamically linked functions
           are compiled with -g.  This appears to be a limitation with
           dld, and can be avoided by not using -g to compile functions
           that will be linked dynamically.

      * fft2 and ifft2 are now built-in functions.

      * The `&&' and `||' logical operators are now evaluated in a
        short-circuit fashion and work differently than the element by
        element operators `&' and `|'.  See the Octave manual for more
        details.

      * Expressions like 1./m are now parsed as 1 ./ m, not 1. / m.

      * The replot command now takes the same arguments as gplot or
        gsplot (except ranges, which cannot be respecified with replot
        (yet)) so you can add additional lines to existing plots.

      * The hold command has been implemented.

      * New function `clearplot' clears the plot window.  The name `clg'
        is aliased to `clearplot' for compatibility with Matlab.

      * The commands `gplot clear' and `gsplot clear' are equivalent to
        `clearplot'.  (Previously, `gplot clear' would evaluate `clear' as
        an ordinary expression and clear all the visible variables.)

      * The Matlab-style plotting commands have been improved.  They now
        accept line-style arguments, multiple x-y pairs, and other plot
        option flags.  For example,

          plot (x, y, "@12", x, y2, x, y3, "4", x, y4, "+")

        results in a plot with

          y  plotted with points of type 2 ("+") and color 1 (red).
          y2 plotted with lines.
          y3 plotted with lines of color 4.
          y4 plotted with points which are "+"s.

        the help message for `plot' and `plot_opt' provide full
        descriptions of the options.

      * NaN is now dropped from plot data, and Inf is converted to a
        very large value before calling gnuplot.

      * Improved load and save commands:

        -- The save and load commands can now read and write a new binary
           file format.  Conversion to and from IEEE big and little endian
           formats is handled automatically.  Conversion for other formats
           has not yet been implemented.

        -- The load command can now read Matlab .mat files, though it is
           not yet able to read sparse matrices or handle conversion for
           all data formats.

        -- The save command can write Matlab .mat files.

        -- The load command automatically determines the save format
           (binary, ascii, or Matlab binary).

        -- The default format for the save command is taken from the
           built-in variable `default_save_format'.

        -- The save and load commands now both accept a list of globbing
           patterns so you can easily load a list of variables from a
           file.

        -- The load command now accepts the option -list, for listing the
           variable names without actually loading the data.  With
           -verbose, it prints a long listing.

        -- The load command now accepts the option -float-binary, for
           saving floating point data in binary files in single precision.

      * who and whos now accept a list of globbing patterns so you can
        limit the lists of variables and functions to those that match a
        given set of patterns.

      * New functions for manipulating polynomials

          compan     -- companion matrix corresponding to polynomial coefficients
          conv       -- convolve two vectors
          deconv     -- deconvolve two vectors
          roots      -- find the roots of a polynomial
          poly       -- characteristic polynomial of a matrix
          polyderiv  -- differentiate a polynomial
          polyinteg  -- integrate a polynomial
          polyreduce -- reduce a polynomial to minimum number of terms
          polyval    -- evaluate a polynomial at a point
          polyvalm   -- evaluate a polynomial in the matrix sense
          residue    -- partial fraction expansion corresponding to the ratio
                        of two polynomials

      * New functions for manipulating sets

          create_set   -- create a set of unique values
          complement   -- find the complement of two sets
          intersection -- find the intersection of two sets
          union        -- find the union of two sets

      * New elementary functions:

          acot   acoth   acsc   acsch
          asec   asech   cot    coth
          csc    csch    log2   sec
          sech

      * New special functions:

          beta   -- beta function
          betai  -- incomplete beta function
          gammai -- incomplete gamma function

      * New image processing functions:

          colormap  -- set and return current colormap
          gray      -- set a gray colormap
          gray2ind  -- image format conversion
          image     -- display an image
          imagesc   -- scale and display an image
          imshow    -- display images
          ind2gray  -- image format conversion
          ind2rgb   -- image format conversion
          loadimage -- load an image from a file
          ntsc2rgb  -- image format conversion
          ocean     -- set a color colormap
          rgb2ind   -- image format conversion
          rgb2ntsc  -- image format conversion
          saveimage -- save an image to a file

      * New time and date funcitons:

          tic          -- set wall-clock timer
          toc          -- get elapsed wall-clock time, since timer last set
          etime        -- another way to get elapsed wall-clock time
          cputime      -- get CPU time used since Octave started
          is_leap_year -- is the given year a leap year?

      * Other new functions:

          bug_report -- submit a bug report to the bug-octave mailing list

          toascii -- convert a string to a matrix of ASCII character codes

          octave_tmp_file -- generate a unique temporary file name

          undo_string_escapes -- replace special characters in a string by
                                 their backslash forms

          is_struct -- determine whether something is a structure data type

          feof   -- check EOF condition for a specified file
          ferror -- check error state for a specified file
          fread  -- read binary data from a file
          fwrite -- write binary data to a file

          file_in_path -- check to see if named file exists in given path

          kbhit  -- get a single character from the terminal

          axis   -- change plot ranges
          hist   -- plot histograms

          diary  -- save commands and output to a file

          type   -- show the definition of a function
          which  -- print the type of an identifier or the location of a
                    function file

          isieee  -- Returns 1 if host uses IEEE floating point
          realmax -- Returns largest floating point number
          realmin -- Returns smallest floating point number

          gcd     -- greatest common divisor
          lcm     -- least common multiple

          null    -- orthonormal basis of the null space of a matrix
          orth    -- orthonormal basis of the range space of a matrix

          fft2    -- two-dimensional fast fourier transform
          ifft2   -- two-dimensional inverse fast fourier transform
          filter  -- digital filter
          fftfilt -- filter using fft
          fftconv -- convolve to vectors using fft
          sinc    -- returns sin(pi*x)/(pi*x)
          freqz   -- compute the frequency response of a filter

      * The meaning of nargin (== args.length ()) in built-in functions
        has been changed to match the meaning of nargin in user-defined
        functions.

      * Variable return lists.  Octave now has a real mechanism for
        handling functions that return an unspecified number of values,
        so it is no longer necessary to place an upper bound on the number
        of outputs that a function can produce.

        Here is an example of a function that uses the new syntax to
        produce n values:

          function [...] = foo (n)
            for i = 1:n
              vr_val (i * x);
            endfor
          endfunction

      * New keyword, all_va_args, that allows the entire list of va_args
        to be passed to another function.  For example, given the functions

          function f (...)
            while (nargin--)
              disp (va_arg ())
            endwhile
          endfunction
          function g (...)
            f ("begin", all_va_args, "end")
          endfunction

        the statement

          g (1, 2, 3)

        prints

          begin
          1
          2
          3
          end

        all_va_args may be used more than once, but can only be used
        within functions that take a variable number of arguments.

      * If given a second argument, svd now returns an economy-sized
        decomposition, eliminating the unecessary rows or columns of U or
        V.

      * The max and min functions correctly handle complex matrices in
        which some columns contain real values only.

      * The find function now handles 2 and 3 output arguments.

      * The qr function now allows computation of QR with pivoting.

      * hilb() is much faster for large matrices.

      * computer() is now a built-in function.

      * pinv() is now a built-in function.

      * The output from the history command now goes through the pager.

      * If a function is called without assigning the result, nargout is
        now correctly set to 0.

      * It is now possible to write functions that only set some return
        values.  For example, calling the function

          function [x, y, z] = f () x = 1; z = 2; endfunction

        as

          [a, b, c] = f ()

        produces:

          a = 1

          b = [](0x0)

          c = 2

      * The shell_cmd function has been renamed to system (the name
        shell_cmd remains for compatibility).  It now returns [output, status].

      * New built-in variable `OCTAVE_VERSION'.  Also a new function,
        version, for compatibility with Matlab.

      * New built-in variable `automatic_replot'.  If it is "true", Octave
        will automatically send a replot command to gnuplot each time the
        plot changes.  Since this is fairly inefficient, the default value
        is "false".

      * New built-in variable `whitespace_in_literal_matrix' allows some
        control over how Octave decides to convert spaces to commas in
        matrix expressions like `[m (1)]'.

        If the value of `whitespace_in_literal_matrix' is "ignore", Octave
        will never insert a comma or a semicolon in a literal matrix list.
        For example, the expression `[1 2]' will result in an error
        instead of being treated the same as `[1, 2]', and the expression

          [ 1, 2,
            3, 4 ]

        will result in the vector [1 2 3 4] instead of a matrix.

        If the value of `whitespace_in_literal_matrix' is "traditional",
        Octave will convert spaces to a comma between identifiers and `('.
        For example, given the matrix

          m = [3 2]

        the expression

          [m (1)]

        will be parsed as

          [m, (1)]

        and will result in

          [3 2 1]

        and the expression

          [ 1, 2,
            3, 4 ]

        will result in a matrix because the newline character is converted
        to a semicolon (row separator) even though there is a comma at the
        end of the first line (trailing commas or semicolons are ignored).
        This is apparently how Matlab behaves.

        Any other value for `whitespace_in_literal_matrix' results in
        behavior that is the same as traditional, except that Octave does
        not convert spaces to a comma between identifiers and `('.
        For example, the expression

          [m (1)]

        will produce 3.  This is the way Octave has always behaved.

      * Line numbers in error messages for functions defined in files and
        for script files now correspond to the file line number, not the
        number of lines after the function keyword appeared.

      * Octave now extracts help from script files.  The comments must
        come before any other statements in the file.

      * In function files, the first block of comments in the file will
        now be interpreted as the help text if it doesn't look like the
        Octave copyright notice.  Otherwise, Octave extracts the first set
        of comments after the function keyword.

      * The function clock is more accurate on systems that have the
        gettimeofday() function.

      * The standard output stream is now automatically flushed before
        reading from stdin with any of the *scanf() functions.

      * Expanded reference card.

      * The Octave distribution now includes a frequently asked questions
        file, with answers.  Better answers and more questions (with
        answers!) are welcome.

      * New option --verbose.  If Octave is invoked with --verbose and not
        --silent, a message is printed if an octaverc file is read while
        Octave is starting.

      * An improved configure script generated by Autoconf 2.0.

      * Lots of bug fixes.

## Summary of changes for version 1.0

      * C-style I/O functions now handle files referenced by name or by
        number more consistently.

## Summary of changes for version 0.83

      * Loading global symbols should work now.

      * Clearing the screen doesn't reprint the prompt unnecessarily.

      * The operations  OP  for OP == +, -,
        *, or ./ no longer crash Octave.

      * More portability and configuration fixes.

## Summary of changes for version 0.82

      * Octave now comes with a reference card.

      * The manual has been improved, but more work remains to be done.

      * The atanh function now works for complex arguments.

      * The asin, acos, acosh, and atanh functions now work properly when
        given real-valued arguments that produce complex results.

      * SEEK_SET, SEEK_CUR, and SEEK_END are now constants.

      * The `using' qualifier now works with gplot and gsplot when the
        data to plot is coming directly from a file.

      * The strcmp function now works correctly for empty strings.

      * Eliminated bogus parse error for M-files that don't end with `end'
        or `endfunction'.

      * For empty matrices with one nonzero dimension, the +, -, .*, and
        ./ operators now correctly preserve the dimension.

      * Octave no longer crashes if you type ^D at the beginning of a line
        in the middle of defining a loop or if statement.

      * On AIX systems, Back off on indexing DiagArray via Proxy class to
        avoid gcc (or possibly AIX assembler?) bug.

      * Various other bug and portability fixes.

## Summary of changes for version 0.81

      * Octave no longer dumps core if you try to define a function in
        your .octaverc file.

      * Fixed bug in Array class that resulted in bogus off-diagonal
        elements when computing eigenvalue and singular value
        decompositions.

      * Fixed bug that prevented lsode from working on the SPARCstation,
        at least with some versions of Sun's f77.  This bug was introduced
        in 0.80, when I changed LSODE to allow the user to abort the
        integration from within the RHS function.

      * Fixed bug that prevented global attribute of variables from being
        saved with save(), and another that prevented load() from working
        at all.

## Summary of changes for version 0.80

      * I have started working on a manual for the C++ classes.  At this
        point, it is little more than a list of function names.  If you
        would like to volunteer to help work on this, please contact
        bug-octave@bevo.che.wisc.edu.

      * The patterns accepted by the save and clear commands now work like
        file name globbing patterns instead of regular expressions.  I
        apologize for any inconvenience this change may cause, but file
        name globbing seems like a more reasonable style of pattern
        matching for this purpose.

      * It is now possible to specify tolerances and other optional inputs
        for dassl, fsolve, lsode, npsol, qpsol, and quad.  For each of
        these functions, there is a corresponding function X_options,
        which takes a keyword and value arguments.  If invoked without any
        arguments, the X_options functions print a list of possible
        keywords and current values.  For example,

          npsol_options ()

        prints a list of possible options with values, and

          npsol_options ("major print level", 10)

        sets the major print level to 10.

        The keyword match is not case sensitive, and the keywords may be
        abbreviated to the shortest unique match.  For example,

          npsol_options ("ma p", 10)

        is equivalent to the statement shown above.

      * The new built-in variable save_precision can be used to set the
        number of digits preserved by the ASCII save command.

      * Assignment of [] now works in most cases to allow you to delete
        rows or columns of matrices and vectors.  For example, given a
        4x5 matrix A, the assignment

          A (3, :) = []

        deletes the third row of A, and the assignment

          A (:, 1:2:5) = []

        deletes the first, third, and fifth columns.

      * Variable argument lists.  Octave now has a real mechanism for
        handling functions that take an unspecified number of arguments,
        so it is no longer necessary to place an upper bound on the number
        of optional arguments that a function can accept.

        Here is an example of a function that uses the new syntax to print
        a header followed by an unspecified number of values:

          function foo (heading, ...)
            disp (heading);
            va_start ();
            while (--nargin)
              disp (va_arg ());
            endwhile
          endfunction

        Note that the argument list must contain at least one named
        argument (this restriction may eventually be removed), and the
        ellipsis must appear as the last element of the argument list.

        Calling va_start() positions an internal pointer to the first
        unnamed argument and allows you to cycle through the arguments
        more than once.  It is not necessary to call va_start() if you
        do not plan to cycle through the arguments more than once.

      * Recursive functions should work now.

      * The environment variable OCTAVE_PATH is now handled in the same
        way as TeX handles TEXINPUTS.  If the path starts with `:', the
        standard path is prepended to the value obtained from the
        environment.  If it ends with `:' the standard path is appended to
        the value obtained from the environment.

      * New functions, from Kurt Hornik (hornik@neuro.tuwien.ac.at) and
        the Department of Probability Theory and Statistics TU Wien,
        Austria:

         corrcoef    -- corrcoef (X, Y) is the correlation between the i-th
                        variable in X and the j-th variable in Y
                        corrcoef (X) is corrcoef (X, X)
         cov         -- cov (X, Y) is the covariance between the i-th
                        variable in X and the j-th variable in Y
                        cov (X) is cov (X, X)
         gls         -- generalized least squares estimation
         kurtosis    -- kurtosis(x) = N^(-1) std(x)^(-4) SUM_i (x(i)-mean(x))^4 - 3
                        If x is a matrix, return the row vector containing
                        the kurtosis of each column
         mahalanobis -- returns Mahalanobis' D-square distance between the
                        multivariate samples X and Y, which must have the
                        same number of components (columns), but may have
                        a different number of observations (rows)
         ols         -- ordinary least squares estimation
         pinv        -- returns the pseudoinverse of X; singular values
                        less than tol are ignored
         skewness    -- skewness (x) = N^(-1) std(x)^(-3) SUM_i (x(i)-mean(x))^3
                        if x is a matrix, return the row vector containing
                        the skewness of each column

      * Errors in user-supplied functions called from dassl, fsolve,
        lsode, npsol, and quad are handled more gracefully.

      * Programming errors in the use of the C++ classes within Octave
        should no longer cause Octave to abort.  Instead, Octave's error
        handler function is called and execution continues as best as is
        possible.  This should result in eventually returning control to
        the top-level Octave prompt.  (It would be nice to have a real
        exception handling mechanism...)

      * A number of memory leaks have been eliminated.  Thanks to
        Fong Kin Fui  for reporting them.

      * The C++ matrix classes are now derived from a generic
        template-based array class.

      * The readline function operate-and-get-next (from bash) is now
        available and bound to C-O by default.

      * Octave now uses the version of readline currently distributed with
        bash-1.13.  On some systems, interactive invocations of Octave
        will now blink the cursor to show matching parens.

      * By default, include files are now installed in
        $prefix/include/octave instead of $prefix/include.

      * Octave now uses a config.h file instead of putting all defines on
        the compiler command line.

## Summary of changes for version 0.79

      * New control systems functions:

         dgram -- Returns the discrete controllability and observability gramian.
         dlqr  -- Discrete linear quadratic regulator design.
         dlqe  -- Discrete linear quadratic estimator (Kalman Filter) design.
         c2d   -- Convert continuous system description to discrete time
                  description assuming zero-order hold and given sample time.

      * The max (min) functions can now return the index of the max (min)
        value as a second return value.

## Summary of changes for version 0.78

      * Octave's handling of global variables has been completely
        rewritten.  To access global variables inside a function, you must
        now declare them to be global within the function body.  Likewise,
        if you do not declare a variable as global at the command line,
        you will not have access to it within a function, even if it is
        declared global there.  For example, given the function

          function f ()
            global x = 1;
            y = 2;
          endfunction

        the global variable `x' is not visible at the top level until the
        command

          octave:13> global x

        has been evaluated, and the variable `y' remains local to the
        function f() even if it is declared global at the top level.

        Clearing a global variable at the top level will remove its global
        scope and leave it undefined.  For example,

          octave:1> function f ()   # Define a function that accesses
          >  global x;              #   the global variable `x'.
          >  x
          > endfunction
          octave:2> global x = 1    # Give the variable `x' a value.
          octave:3> f ()            # Evaluating the function accesses the
          x = 1                     #   global `x'.
          octave:4> clear x         # Remove `x' from global scope, clear value.
          octave:5> x = 2           # Define new local `x' at the top level
          x = 2
          octave:6> f               # The global `x' is no longer defined.
          error: `x' undefined near line 1 column 25
          error: evaluating expression near line 1, column 25
          error: called from `f'
          octave:7> x               # But the local one is.
          x = 2

      * The new function, `is_global (string)' returns 1 if the variable
        named by string is globally visible.  Otherwise, returns 0.

      * The implementation of `who' has changed.  It now accepts the
        following options:

          -b -builtins   -- display info for built-in variables and functions
          -f -functions  -- display info for currently compiled functions
          -v -variables  -- display info for user variables
          -l -long       -- display long info

        The long output looks like this:

          octave:5> who -l

          *** currently compiled functions:

          prot  type               rows   cols  name
          ====  ====               ====   ====  ====
           wd   user function         -      -  f

          *** local user variables:

          prot  type               rows   cols  name
          ====  ====               ====   ====  ====
           wd   real scalar           1      1  y

          *** globally visible user variables:

          prot  type               rows   cols  name
          ====  ====               ====   ====  ====
           wd   complex matrix       13     13  x

        where the first character of the `protection' field is `w' if the
        symbol can be redefined, and `-' if it has read-only access.  The
        second character may be `d' if the symbol can be deleted, or `-'
        if the symbol cannot be cleared.

      * The new built-in variable ignore_function_time_stamp can be used
        to prevent Octave from calling stat() each time it looks up
        functions defined in M-files.  If set to "system", Octave will not
        automatically recompile M-files in subdirectories of
        $OCTAVE_HOME/lib/VERSION if they have changed since they were last
        compiled, but will recompile other M-files in the LOADPATH if they
        change.  If set to "all", Octave will not recompile any M-files
        unless their definitions are removed with clear.  For any other
        value of ignore_function_time_stamp, Octave will always check to
        see if functions defined in M-files need to recompiled.  The
        default value of ignore_function_time_stamp is "system".

      * The new built-in variable EDITOR can be used to specify the editor
        for the edit_history command.  It is set to the value of the
        environment variable EDITOR, or `vi' if EDITOR is not set, or is
        empty.

      * There is a new built-in variable, INFO_FILE, which is used as the
        location of the info file.  Its initial value is
        $OCTAVE_HOME/info/octave.info, so `help -i' should now work
        provided that OCTAVE_HOME is set correctly, even if Octave is
        installed in a directory different from that specified at compile
        time.

      * There is a new command line option, --info-file FILE, that may be
        used to set Octave's idea of the location of the info file.  It
        will override any value of OCTAVE_INFO_FILE found in the
        environment, but not any INFO_FILE="filename" commands found in
        the system or user startup files.

      * Octave's Info reader will now recognize gzipped files that have
        names ending in `.gz'.

      * The save command now accepts regular expressions as arguments.
        Note that these patterns are regular expressions, and do not work
        like filename globbing.  For example, given the variables `a',
        `aa', and `a1', the command `save a*' saves `a' and `aa' but not
        `a1'.  To match all variables beginning with `a', you must use an
        expression like `a.*' (match all sequences beginning with `a'
        followed by zero or more characters).

      * Line and column information is included in more error messages.

## Summary of changes for version 0.77

      * Improved help.  The command `help -i topic' now uses the GNU Info
        browser to display help for the given topic directly from the
        Texinfo documenation.

      * New function: chol -- Cholesky factorization.

## Summary of changes for version 0.76

      * Better run-time error messages.  Many now include line and column
        information indicating where the error occurred.  Octave will also
        print a traceback for errors occurring inside functions. If you
        find error messages that could use improvement, or errors that
        Octave fails to catch, please send a bug report to
        bug-octave@bevo.che.wisc.edu.

      * If gplot (or gsplot) is given a string to plot, and the string
        does not name a file, Octave will pass the string along to gnuplot
        directly.  This allows commands like

          gplot "sin (x)" w l, data w p

        to work (assuming that data is a variable containing a matrix of
        values).

      * Long options (--help, --version, etc.) are supported.

## Summary of changes for version 0.75

      * The documentation is much more complete, but still could use a lot
        of work.

      * The history function now prints line numbers by default.  The
        command `history -q' will  omit them.

      * The clear function now accepts regular expressions.

      * If gplot (or gsplot) is given a string to plot, and the string
        names a file, Octave attempts to plot the contents of the file.

      * New functions:

        history:

          run_history  -- run commands from the history list.
          edit_history -- edit commands from the history list with your
                          favorite editor.

        linear algebra:

          balance         -- Balancing for algebraic and generalized
                             eigenvalue problems.
          givens          -- Givens rotation.
          is_square       -- Check to see if a matrix is square.
          qzhess          -- QZ decomposition of the matrix pencil (a - lambda b).
          qzval           -- Generalized eigenvalues for real matrices.
          syl             -- Sylvester equation solver.

        control systems:

          is_symmetric    -- Check to see if a matrix is symmetric.
          abcddim         -- Check dimensions of linear dynamic system [A,B,C,D].
          is_controllable -- Check to see if [A,B,C,D] is controllable.
          is_observable   -- Check to see if [A,B,C,D] is observable.
          are             -- Solve algebraic Ricatti equation.
          dare            -- Solve discrete-time algebraic Ricatti equation.
          lqe             -- Kalman filter design for continuous linear system.
          lqr             -- Linear Quadratic Regulator design.
          lyap            -- Solve Lyapunov equation.
          dlyap           -- Solve discrete Lyapunov equation.
          tzero           -- Compute the transmission zeros of [A,B,C,D].

## Summary of changes for version 0.74

      * Formal parameters to functions are now always considered to be
        local variables, so things like

          global x = 0
          global y = 0
          function y = f (x) x = 1; y = x; end
          f (x)

        result in the function returning 1, with the global values of x
        and y unchanged.

      * Multiple assignment expressions are now allowed to take indices,
        so things like

          octave:13> [a([1,2],[3,4]), b([5,6],[7,8])] = lu ([1,2;3,4])

        will work correctly.

## Summary of changes for version 0.73

      * Saving and loading global variables works correctly now.

      * The save command no longer saves built-in variables.

      * Global variables are more reliable.

      * Matrices may now have one or both dimensions zero, so that
        operations on empty matrices are now handled more consistently.

        By default, dimensions of the empty matrix are now printed along
        with the empty matrix symbol, `[]'.  For example:

          octave:13> zeros (3, 0)
          ans =

          [](3x0)

        The new variable `print_empty_dimensions' controls this behavior.

        See also Carl de Boor, An Empty Exercise, SIGNUM, Volume 25,
        pages 2--6, 1990, or C. N. Nett and W. M. Haddad, A
        System-Theoretic Appropriate Realization of the Empty Matrix
        Concept, IEEE Transactions on Automatic Control, Volume 38,
        Number 5, May 1993.

      * The right and left division operators `/' and `\' will now find a
        minimum norm solution if the system is not square, or if the
        coefficient matrix is singular.

      * New functions:

          hess   -- Hessenberg decomposition
          schur  -- Ordered Schur factorization
          perror -- print error messages corresponding to error codes
                    returned from the functions fsolve, npsol, and qpsol
                    (with others to possibly be added later).

      * Octave now prints a warning if it finds anything other than
        whitespace or comments after the final `end' or `endfunction'
        statement.

      * The bodies of functions, and the for, while, and if commands are
        now allowed to be empty.

      * Support for Gill and Murray's QPSOL has been added.  Like NPSOL,
        QPSOL is not freely redistributable either, so you must obtain
        your own copy to be able to use this feature.  More information
        about where to find QPSOL and NPSOL are in the file README.NLP.

## Summary of changes for version 0.72

      * For numeric output, columns are now lined up on the decimal point.
        (This requires libg++-2.3.1 or later to work correctly).

      * If octave is running interactively and the output intended for the
        screen is longer than one page and a pager is available, it is
        sent to the pager through a pipe.  You may specify the program to
        use as the pager by setting the variable PAGER.  PAGER may also
        specify a command pipeline.

      * Spaces are not always significant inside square brackets now, so
        commands like

          [ linspace (1, 2) ]

        will work.  However, some possible sources of confusion remain
        because Octave tries (possibly too hard) to determine exactly what
        operation is intended from the context surrounding an operator.
        For example:

        -- In the command

             [ 1 - 1 ]

           the `-' is treated as a binary operator and the result is the
           scalar 0, but in the command

             [ 1 -1 ]

           the `-' is treated as a unary operator and the result is the
           vector [ 1 -1 ].

        -- In the command

             a = 1; [ 1 a' ]

           the single quote character `'' is treated as a transpose operator
           and the result is the vector [ 1 1 ], but in the command

             a = 1; [ 1 a ' ]

           an error message indicating an unterminated string constant is
           printed.

      * Assignments are just expressions now, so they are valid anywhere
        other expressions are.  This means that things like

          if (a = n < m) ... endif

        are valid.  This is parsed as:  compare `n < m', assign the result
        to the variable `a', and use it as the test expression in the if
        statement.

        To help avoid errors where `=' has been used but `==' was
        intended, Octave issues a warning suggesting parenthesis around
        assignments used as truth values.  You can suppress this warning
        by adding parenthesis, or by setting the value of the new built-in
        variable `warn_assign_as_truth_value' to 'false' (the default
        value is 'true').

        This is also true for multiple assignments, so expressions like

          [a, b, c] = [u, s, v] = expression

        are now possible.  If the expression is a function, nargout is set
        to the number of arguments for the right-most assignment.  The
        other assignments need not contain the same number of elements.
        Extra left hand side variables in an assignment become undefined.

      * The default line style for plots is now `lines' instead of
        `points'.  To change it, use the `set data style STYLE' command.

      * New file handling and I/O functions:

          fopen    -- open a file for reading or writing
          fclose   -- close a file
          fflush   -- flush output to a file
          fgets    -- read characters from a file
          frewind  -- set file position to the beginning of a file
          fseek    -- set file position
          ftell    -- tell file position
          freport  -- print a report for all open files
          fscanf   -- read from a file
          sscanf   -- read from a string
          scanf    -- read from the standard input

      * New built-in variables for file and I/O functions:

          stdin    -- file number corresponding to the standard input stream.
          stdout   -- file number corresponding to the standard output stream.
          stderr   -- file number corresponding to the standard error stream.

        The following may be used as the final (optional) argument for
        fseek:

          SEEK_SET -- set position relative to the beginning of the file.
          SEEK_CUR -- set position relative to the current position.
          SEEK_END -- set position relative to the end of the file.

      * New function: setstr -- convert vectors or scalars to strings
        (doesn't work for matrices yet).

      * If possible, computer now prints the system type instead of
        always printing `Hi Dave, I'm a HAL-9000'.

      * Octave now properly saves and restores its internal state
        correctly in more places.  Interrupting Octave while it is
        executing a script file no longer causes it to exit.

      * Octave now does tilde expansion on each element of the LOADPATH.

      * A number of memory leaks have been plugged.

      * Dependencies for C++ source files are now generated automatically
        by g++.

      * There is a new command line option, -p PATH, that may be used to
        set Octave's loadpath from the command line.  It will override any
        value of OCTAVE_PATH found in the environment, but not any
        LOADPATH="path" commands found in the system or user startup files.

      * It is now possible to override Octave's default idea of the
        location of the system-wide startup file (usually stored in
        $(prefix)/lib/octave/octaverc) using the environment variable
        OCTAVE_HOME.  If OCTAVE_HOME has a value, Octave will look for
        octaverc and its M-files in the directory $OCTAVE_HOME/lib/octave.

        This allows people who are using binary distributions (as is
        common with systems like Linux) to install the real octave binary
        in any directory (using a name like octave.bin) and then install
        a simple script like this

          #!/bin/sh
          OCTAVE_HOME=/foo/bar/baz
          export OCTAVE_HOME
          exec octave.bin

        to be invoked as octave.

## Summary of changes for version 0.71

      * Much improved plotting facility.  With this release, Octave does
        not require a specially modified version of gnuplot, so gnuplot
        sources are no longer distributed with Octave.  For a more
        detailed description of the new plotting features, see the file
        PLOTTING.

      * New plotting commands:

          plot            -- 2D plots
          semilogx        -- 2D semilog plot with logscale on the x axis
          semilogy        -- 2D semilog plot with logscale on the y axis
          loglog          -- 2D log-log plot
          mesh            -- 3D mesh plot
          meshdom         -- create matrices for 3D plotting from two vectors
          contour         -- contour plots of 3D data
          bar             -- create bar graphs
          stairs          -- create stairstep plots
          polar           -- 2D plots from theta-R data
          grid            -- turn plot grid lines on or off
          xlabel, ylabel  -- place labels on the x and y axes of 2D plots
          sombrero        -- demonstrate 3D plotting
          gplot           -- 2D plot command with gnuplot-like syntax
          gsplot          -- 3D plot command with gnuplot-like syntax
          set             -- set plot options with gnuplot syntax
          show            -- show plot options with gnuplot syntax
          closeplot       -- close stream to gnuplot process
          purge_tmp_files -- delete temporary files created by plot command

      * Other new commands:

          ls, dir         -- print a directory listing
          shell_cmd       -- execute shell commands
          keyboard        -- get input from keyboard, useful for debugging
          menu            -- display a menu of options and ask for input
          fft             -- fast fourier transform
          ifft            -- inverse fast fourier transform

      * Strings may be enclosed in either single or double quote
        characters.  Double quote characters are not special within single
        quote strings, and single quotes are not special within double
        quote strings.

      * Command name completion now works for M-file names too.

      * Better help and usage messages for many functions.

      * Help is now available for functions defined in M-files.  The first
        block of comments is taken as the text of the help message.

      * Numerous changes in preparation to support dynamic loading of
        object files with dld.

      * Bug fixes to make solving DAEs with dassl actually work.

      * The command `save file' now saves all variables in the named file.

      * If do_fortran_indexing is 'true', indexing a scalar with
        [1,1,1,...] (n times) replicates its value n times.  The
        orientation of the resulting vector depends on the value of
        prefer_column_vectors.

      * Things like [[1,2][3,4]] no longer cause core dumps, and invalid
        input like [1,2;3,4,[5,6]] now produces a diagnositic message.

      * The cd, save, and load commands now do tilde expansion.

      * It's now possible to clear global variables and functions by name.

      * Use of clear inside functions is now a parse error.

## Summary of changes for version 0.70

      * Better parse error diagnostics.  For interactive input, you get
        messages like

          octave:1> a = 3 + * 4;

          parse error:

              a = 3 + * 4;
                      ^

        and for script files, the message includes the file name and input
        line number:

          octave:1> foo

          parse error near line 4 of file foo.m:

              a = 3 + * 4;
                      ^

      * New built-in variable PS2 which is used as the secondary prompt.
        The default value is '> '.

      * New file, octave-mode.el, for editing Octave code with GNU Emacs.
        This is a modified version of Matthew R. Wette's matlab-mode.el.

      * Better support for missing math functions.

      * User preferences are now cached in a global struct so we don't
        have to do a symbol table lookup each time we need to know what
        they are.  This should mean slightly improved performance for
        evaluating expressions.

## Summary of changes for version 0.69

      * Multiple assignments are now possible, so statements like

          a = b = c = 3;
          a = b = c = [1,2;3,4];

        or

          c = (a = (b = 2) * 3 + 4) * 5

        are legal, as are things that have even more bizarre effects, like

          a(4:6,4:6) = b(2:3,2:3) = [1,2;3,4];

        (try it).

      * Improved parsing of strings (but they still don't work as matrix
        elements).

      * An M-file may now either define a function or be a list of
        commands to execute.

      * Better detection and conditional compilation of IEEE functions
        isinf, finite, and isnan.

      * Replacements for acosh, asinh, atanh, and gamma from the BSD math
        library for those systems that don't have them.

## Summary of changes for version 0.68

      * New functions:

          eval  -- evaluate a string as a sequence of Octave commands.
          input -- print a prompt and get user input.

## Summary of changes for version 0.67

      * New functions:

          find -- return the indices of nonzero elements.

      * Zero-one style indexing now works.  For example,

          a = [1,2,3,4];
          b = a([1,0,0,1])

        sets b to the first and fourth elememnts of a.

        Zero-one style indexing also works for indexing the left hand side
        of an assignment.  For example,

          a = rand (1,2;3,4);
          a([0,1],:) = [-1,-2]

        sets the second row of a to [-1 -2]

        The behavior for the ambiguous case

          a = [1,2,3,4];
          b = a([1,1,1,1]);

        is controlled by the new global variable `prefer_zero_one_indexing'.
        If this variable is equal to 'true', b will be set to [1 2 3 4].
        If it is false, b will be set to [1 1 1 1].  The default value is
        'false'.

      * Using the new global variable `propagate_empty_matrices', it is
        possible to have unary andy binary operations on empty matrices
        return an empty matrix.  The default value of this variable is
        'warn', so that empty matrices are propagated but you get a
        warning.  Some functions, like eig and svd have also been changed
        to handle this.

      * Empty matrices can be used in conditionals, but they always
        evaluate to `false'.  With propagate_empty_matrices = 'true', both
        of the following expressions print 0:

          if  [], 1, else 0, end
          if ~[], 1, else 0, end

      * Octave no longer converts input like `3.2 i' or `3 I' to complex
        constants directly because that causes problems inside square
        brackets, where spaces are important.  This abbreviated notation
        *does* work if there isn't a space between the number and the i,
        I, j, or J.

## Summary of changes for version 0.66

      * Logical unary not operator (~ or !) now works for complex.

      * Left division works.

      * Right and left element by element division should work correctly
        now.

      * Numbers like .3e+2 are no longer errors.

      * Indexing a matrix with a complex value doesn't cause a core dump.

      * The min and max functions should work correctly for two arguments.

      * Improved (I hope!) configuration checks.

      * Octave is now installed as octave-M.N, where M and N are version
        numbers, and octave is a link to that file.  This makes it
        possible to have more than one version of the interpreter installed.

## Summary of changes for version 0.63

      * The reshape function works again.

      * Octave now converts input like `3.2i' or `3 I' or `2.3e5 j' to be
        complex constants directly, rather than requiring an expression
        like `3.3 * i' to be evaluated.

## Summary of changes for version 0.61

      * Octave has been successfully compiled using gcc 2.3.3 and libg++ 2.3.
        on a 486 system running Linux.

      * The win_texas_lotto function is now called texas_lotto (it's a
        script file, and win_texas_lotto.m is too long for some Linux and
        System V systems).

## Summary of changes for version 0.57

      * The C-like formatted print functions printf, fprintf, and sprintf
        finally work.

## Summary of changes for version 0.56

      * By default, octave prints a short disclaimer when it starts.
        (You can suppress it by invoking octave with -q).

      * You can keep octave from reading your ~/.octaverc and .octaverc
        files by invoking it with -f.

      * When returning two values, eig now returns [v, d] instead of
        [lambda, v], where d is a diagonal matrix made from lambda.

      * The win_texas_lotto function now produces a sorted list.

      * New functions:

          expm -- matrix exponential.
          logm -- matrix logarithm.

## Summary of changes for version 0.55

      * The following (C-style) backslash escape sequences work in quoted
        strings (useful(?) with printf()):

          \a  bell         \r  carriage return
          \b  backspace    \t  horizontal tab
          \f  formfeed     \v  vertical tab
          \n  newline      \\  backslash

      * Use of `...' at the end of a line will allow a statement to
        continue over more than one line.

      * The names `inf' and `nan' are now aliases for `Inf' and `NaN',
        respectively.

      * New functions:

          casesen -- print a warning if the luser tries to turn off case
                     sensitivity.
          median  -- find median value.
          norm    -- compute the norm of a matrix.
          sort    -- sort columns.

      * New variable, `silent_functions'.  If silent_functions == 'true',
        the results of expressions are not printed even if they are not
        followed by a semicolon.  The disp() and printf() functions still
        result in output.  The default value for this variable is 'false'.

      * New variable `return_last_value_computed'.  If it is 'true',
        functions defined in script files return the last value computed
        if a return value has not been explicitly declared.  The default
        value for this variable is 'false'.

## Summary of changes for version 0.52

      * Name completion works for function and variable names currently in
        the symbol tables.  Coming soon: completion for names of functions
        defined in script files but not yet compiled.

      * The initial value of do_fortran_indexing is now false, and the
        initial value of prefer_column_vectors is now true.  Swap the
        values of these variables if you want behavior that is more like
        Matlab.

      * All script files check the number of input arguments before doing
        much real work.

      * The identifiers `i' and `j' are now also names for sqrt(-1).
        These symbols may be used for other purposes, but their original
        definition will reappear if they are cleared.

      * The symbol tables are now implemented with hash tables for faster
        searching.

      * A small amount of help is now available for most built-in
        operators, keywords and functions.  Coming soon: help for script
        files.

      * Without any arguments, the help command now lists all known
        built-in operators, keywords and functions.

      * Generic parse errors are now signalled by `Eh, what's up doc?',
        which is closer to what Bugs actually says.

      * The who command now only prints variable names by default.
        Use the -fcn (or -fcns, or -functions) switch to print the names of
        built-in or currently compiled functions.

## Summary of changes for version 0.51

      * Major overhaul of array indexing.

      * The colloc function actually works now.

## Summary of changes for version 0.50

      * The lsode and dassl functions now return the states only,
        instead of the time and the states, so you must keep track of
        the corresponding times (this is easy though, because you have
        to specify a vector of desired output times anyway).

      * Solution of NLPs with NPSOL now works on the SPARC.

      * New keywords `endif', `endfor', `endfunction', `endif', and
        `endwhile', which allow for better diagnostics.  The `end' keyword
        is still recognized.  All script files have been changed to use
        these new keywords in place of `end'.

      * It is now possible to uninstall Octave by doing a `make uninstall'
        in the top level directory.

      * The Makefiles are much closer to conforming with GNU coding standards.

      * New functions:

          win_texas_lotto  -- produce six unique random numbers between 1 and 50.
          quad             -- numerical integration.
          lu               -- LU factorization
          qr               -- QR factorization
          dassl            -- Solution of DAEs using DASSL.

      * New files:

          THANKS -- A list of people and organazations who have supported
                    the development of Octave.

          NEWS   -- This file, listing recent changes.

      * Help is now available at the gnuplot prompt.