![[Icon home]](wwwcube.gif)
Gregg M. Townsend
Department of Computer Science
The University of Arizona
www.cs.arizona.edu/icon/v950/relnotes.htm
Last updated April 12, 2010
Version 9.5.0 of Icon is an update of version 9.4.3 of Icon. It incorporates configuration, documentation, and library changes. Some minor bugs have been fixed. Support has been added for "external values" created by user C functions.
Notable changes in this latest version are listed here. Some code cleanup work and documentation editing has also been done.
External code incorporated by loadfunc() can now create
and return to Icon code opaque values that can be stored and passed
on subsequent calls.
This is similar to a feature of the early Macintosh ProIcon implementation.
See External Values for more information.
This version of Icon is the first to deliberately move beyond the 1989 C standard and make use of features of the 1999 C standard, specifically the "struct hack". Consequently, a C99 (or newer) compiler is now required to build Icon.
The cygwin configuration has improved, partially through
removal of unneeded special cases now that Cygwin better approximates Unix.
External functions can now be loaded using loadfunc().
In addition to the cygwin configuration, which uses
Windows graphics, there is now a new xcygwin configuration
that uses the X window system.
Large amounts of conditionalized dead code, including the old Icon compiler, have been removed from the source code.
All platforms now use POSIX threads for context switching instead of system- and processor-dependent assembly language code.
The loadfunc() implementation now specifies to the system
that C globals are to be shared with and among loaded functions.
The command icon nonexistent.icn no longer leaves debris
in the /tmp directory.
The maximum length of a file name has been increased from 256 to 512 characters.
Table copying in the Sparc (Solaris) configuration was fixed by coding a workaround to avoid a GCC 4.2.2 struct assignment bug.
As usual, some files in the Icon program library have been added or edited, but the core library files remain stable. Notable changes include:
procs/echo New procedure for interpolating variables in strings. procs/printf Rewrite parts to fix several bugs, and add test. procs/random Improve thoroughness of randomize(). progs/diffsum Handle output of "cvs diff". progs/unclog Handle CVS branches; fix indentation. progs/weblinks Add option to sort output by referencing page. gprogs/breakout Make the ball large enough to see. gprogs/gallery Treat -wnnn and -hnnn options as *minimums*. gprogs/gallery Handle spaces embedded in JPEG filenames. gprogs/kaleid Add delay to prevent runaway on fast CPUs. gprogs/spider Add shortcuts, opt-in logging, congratulatory display. gprogs/trkvu Limit file legend to onscreen files. gprogs/tron New video game inspired by Tron. packs/loadfuncpp Add C++ interface package. packs/icondb Add MySQL interface package. gpacks/weaving Add "halftone" weaving program htweav.icn.
Two new documentation pages, Loading C functions and External Values, have been added.
These features appeared in earlier releases of Icon but subsequent to publication of the Icon books.
Icon's X-windows interface no longer limits each window to 256 colors at one time. Median-cut quantization selects image colors when writing a GIF file.
An Icon source file can be made executable under Unix by prefixing it with a comment line
#!/usr/bin/env iconicon command,
which in another form allows a small Icon program to be embedded
within a shell script.
See the man page for details.
The traditional icont command
remains available when more flexibility is needed.
Under Unix, colons (:) may now separate directories in the
LPATH and IPATH environment variables as an
alternative to spaces.
The Icon translator and linker search these paths when looking for
$include and link files respectively.
The Icon program library is now searched automatically, but
LPATH and IPATH can still be set to control
the search order.
The effective path in each case is:
Other changes affect the configuration of Icon at installation time and the way executable Icon programs locate the interpreter. These changes, which are transparent to most users, are discussed in more detail on the File Organization page.
The files in a directory can be listed by opening the directory as a file.
Subsequent reads return the names of the files contained in the directory.
The names are returned in no particular order, and for Unix, the directories
"." and ".." are included.
The function read() recognizes
three kinds of line terminators when reading a file
opened in translated mode:
Windows (CR+LF), Macintosh (CR), or Unix (LF).
Consequently, text files created on one platform can be
read by an Icon program running on a different platform.
Large integers cannot be used with i to j,
with seq(), or with integer-valued keywords.
Large-integer literals are constructed at run-time, so such literals are best kept outside of loops.
Conversion of a large integer to a string is quadratic in the length of the integer. Conversion of a very large integer may take a long time.
An "evaluation stack overflow" can occur when a procedure is called
with a huge number (thousands or more) of arguments.
The capacity can be increased by setting the environment variable
MSTKSIZE or COEXPSIZE, as appropriate.
Stack overflow checking uses a heuristic that is not always effective. Stack overflow in a co-expression is especially likely to escape detection and cause a mysterious program malfunction.
Pathologically nested structures can provoke a memory or segmentation
fault during garbage collection by reaching the stack limit.
The stack limit can be raised by the
limit or ulimit shell command.
If an expression such as x := create expr
is used in a loop, and x is not a global variable,
uncollectable co-expressions accumulate with each iteration.
This problem can be circumvented by making x
a global variable or by assigning a value to x
before the create operation, as in
x := &null
x := create expr
Integer overflow on exponentiation may not be detected during execution. Such overflow may occur during type conversion.
See the documentation guide for an overview of the available Icon documentation.
For installation instructions, see Installing Binaries or Building from Source as appropriate.
Carl Sturtivant inspired and participated in the development
of external values. He also contributed the loadfuncpp
and icondb packages.
Eduardo Ochs contributed the tron game.
Charles L. Hethcoat III contributed the echo procedure.
Carl Sturtivant and Steve Waldo supplied numerous Cygwin improvements.
Cheyenne Wills improved the flexibility of the configuration process.
Clint Jeffery fixed an ancient linking bug.
Robert Shiplett and Jonathan Kaye helped with testing.