makeThe current status of this entry is:
STATUS: doesn't work with some platforms - please help us fixFor more detailed information see 2011 richards bugs.
echo expression | ./richards./try.shOh no, yet another
dc-style calculator? (see
2000/dlowe using an embedded Perl interpreter and deemed Worst Abuse of the Rules). Well, this one does it (expression calculation, that is,
not the rule abuse) in a different way. The author claims that his calculator
does just-in-time compilation. What would you do to prove or disprove his claim
without attempting to unravel the source?
This is an implementation of the classic UNIX
dc command, the
reverse Polish
calculator. Actually it’s a pretty bad implementation, since it only implements
32-bit integers (well, sizeof(int)-sized integers). It only implements the
commands +, -, *, /, p (only for numbers), register stacks, macros and
comparisons. Wow, you’d think I could’ve done better in 2K of code.
OH! I forgot to mention! It’s a JIT.
Wait, don’t stop reading! I know what you’re thinking, platform-specific code is discouraged in IOCCC. But do you see any platform-specific code? There’s no assembler here! This JIT works on a dozen platforms, and the only platform-specific assumptions it makes are that the stack grows down and integers are at least 32-bit.
You will probably get warnings while compiling the code. In particular:
If your system requires the inclusion of alloca.h to use alloca, use the
compile flag -DAH.
If your system cannot use mmap(), use the compile flag -DNM.
I don’t include any headers I don’t strictly need to, so you’ll get warnings
about (at least) memcpy(), isdigit(), atoi(), calloc(), malloc()
and alloca() if you didn’t use -DAH.
GCC likes to complain about while (a = b) (assignments as a condition).
I don’t return from main(), even though it’s declared to return int.
Platforms on which all known/tested optimization levels work with no additional flags:
Platforms which work but not at all optimization levels or needing special flags:
-DNM -DAH -fno-stack-check