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Gregg M. Townsend
Department of Computer Science
The University of Arizona
www.cs.arizona.edu/icon/v951/relnotes.htm
Last updated June 5, 2013
Version 9.5.1 of Icon is an update of version 9.5.0. It incorporates configuration, library, and documentation changes. An execution profiler has been added and there are a few new example programs. Some minor bugs have been fixed.
These notes document:
Notable changes in this latest version are listed here.
An execution profile can be produced by setting the environment variable
ICONPROFILE at execution time to specify an output file.
For a separately built program, profiling must also be enabled during linking.
For each line of the program that is executed, the profiler reports the number of visits and also the number of timer ticks attributed to the line.
The report is ordered by memory layout, which is based on linkage order.
To arrange by filename, use the Unix sort utility
with keys –k3,3 –k4n.
To see the CPU hotspots, use sort –nr | head.
A QUIT signal (^\) is now caught to produce
a traceback message.
If profiling has been enabled, the profile report is also generated.
The command
icon filename.icn now searches first in the
directory of filename for $include files.
Pipes can now be opened in untranslated mode.
A memory leak on every 25th co-expression allocation has been fixed.
The external value examples have been rewritten for standards compliance.
Some configurations have been modified in response to changes in their underlying platforms.
Some perfectly legal code has been tweaked to avoid provoking well-intentioned warning messages from C compilers.
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/io Honor "len" parameter in tempname() procs/itlib Use infocmp utility if no termcap file procs/levensht Add procedure for computing Levenshtein edit distance procs/numbers Add quadratic mean procedure qmean(L) procs/numbers Fix spell(i) procedure procs/psrecord Fix positioning of noncircular arcs progs/iprofl Add program for listing source with execution profile progs/lisp Read from standard input after reading named file gprogs/mandel3 Add Mandelbrot Set display gprogs/othello Add interactive Othello board game gprogs/tess Add 4-D tesseract display
There is now a single Cygwin configuration. It uses the X Window System if built with graphics enabled. The alternate configuration using native Windows graphics is no longer supported, and its non-standard compatibility functions are no longer available.
These features appeared in earlier releases of Icon but subsequent to publication of the Icon books.
External code incorporated by loadfunc() can now create
and return to Icon code opaque values that can be stored and passed
on subsequent calls.
See External Values for more information.
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.
Icon deals strictly in 8-bit characters and expects a superset of ASCII such as ISO 8859-1 (“Latin 1”). It does not translate UTF-8 escape sequences and does not support Unicode.
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.
Icon graphics facilities utilize only server-side fonts (those listed
by xlsfonts) and not the more modern client-side fonts.
Now that graphics memory is cheap, very few platforms require or support mutable colors. Icon code for mutable colors is still present but untested.
Windows are not always refreshed properly while a program is blocked awaiting standard input.
Depending on the window manager, values set and read back from the
pos, posx, and posy attributes
may be slightly inconsistent.
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 updated and maintained the Cygwin configuration. Jafar Al-Gharaibeh discovered two problems with co-expression switching and supplied corrective code.
Greg Buchholz published the mandel3 program in comp.lang.icon.
Chris Tenaglia contributed the tess program.
David Gamey contributed the quadratic mean procedure qmean()
as well as a fix for spell().
Jeremy Cowgar supplied the levenshtein() procedure.
Will Evans provided the fix for the PostScript recorder psrecord.
Clint Jeffery supplied the itlib fix.
Phillip Thomas and Clint Jeffery modified the lisp program.
Tom Christopher supplied the tempname fix in some very
old mail that was recently rediscovered.