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Gregg M. Townsend
Department of Computer Science
The University of Arizona
www.cs.arizona.edu/icon/v943/relnotes.htm
Last updated November 10, 2005
Version 9.4.3 of Icon is a minor update to version 9.4.2 of Icon. It incorporates configuration, documentation, and library updates. Some minor bugs have been fixed.
The Icon language is unchanged, and this Unix implementation remains compatible at the source level with Icon 9.3 for Windows.
Notable changes in this latest version are listed here. Some code cleanup work and documentation editing has also been done.
The system-specific Icon configurations have been reorganized and renamed; new names focus on operating systems rather than CPU architectures. The several BSD configurations have been merged into one.
The macintosh configuration now supports the
loadfunc function. This configuration has also been
revised to anticipate Apple's announced migration to the x86 architecture.
A new porting guide has been written, and a new
posix configuration has been added
as a starting point in constructing new ports.
As usual, several files in the Icon program library have been added or edited. The core library files, however, remain stable. Notable changes include:
procs/dijkstra new procedures implement Dijkstra's control structures procs/html add procedure for canonicalization of paths procs/matrix2 new procedures for matrix manipulation procs/nestlist new procedures for representing nested lists as strings procs/printf add %e format and fix a rounding problem progs/noise new program for producing a random bitstream progs/unclog improve logic for combining adjacent entries gprogs/dlgvu improve coverage map; allow altitude in GPS data gprogs/gallery faster thumbnail loading for JPEG images gprogs/img many new features gprogs/sier better color choices gprogs/trkvu accept GPS track logs with altitude as the last fieldThe undocumented
save function, which only worked
on a few platforms, has been removed.
These features appeared in earlier releases of Icon that followed 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 for less specialized purposes.
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.
For version 9.4, 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.
Arthur Eschenlauer contributed the matrix2
and nestlist libraries.
Frank Lhota contributed the dijkstra library.
Nolan Clayton contributed revisions to the img program.
Michael Glass contributed revisions to the printf procedure.
Chris Tenaglia and Andreas Almroth contributed configuration files.