ioccc/2001/schweikh

Best one-liner:

Jens Schweikhardt
Marconi Communications
Schlartaeckerweg 3
D-71384 Weinstadt
Germany

http://www.schweikhardt.net/

To build:

make

To run:

./schweikh string string2

Try:

./schweikh foo 'f??'; echo $?
./schweikh 'best short program' '??st*o**p?*'; echo $?
./schweikh bar 'f??'; echo $?

Judges' comments:

Do you get the pattern here?

Author's comments:

This one-liner program is a glob pattern matcher. It understands the glob characters *' meaning zero or more characters' and `?' meaning exactly one character, just like your unix shell.

Run it with two args, the string and the glob pattern. The exit status is 0 (shell true) when the pattern matches, 1 otherwise. The glob pattern must match the whole string, so you may want to use * at the beginning and end of the pattern if you are looking for something in the middle.

You can use it for your shell scripting needs similar to a silent grep (and without stdout redirected to /dev/null):

if prog "${VARIABLE}" '<glob>'; then
    echo VARIABLE matches
else
    echo no match
fi

Bugs: there is no way to escape the meta characters. Dammit Jim, I'm a one-liner, not a regexp lib.

All obfuscation is obviously in the recursive m() function, an 86 character glob pattern evaluator, returning nonzero for a match:

• just a single complex return expression.
• nested ternary operator ?: to save on if/else verbosity.
• short circuiting && and || to save even more on if/else verbosity.
• Subtraction instead of an equality operator in "*t - 42".
• ASCII codes for '*' and '?'.
• careful use of blanks even though this year's rules have extended that resource limit.
• the source is a complete preprocessed C program. Because it communicates with the world out there by means of argv and the exit status, there is no need for stdio bloat. An asm guru could surely squeeze this program in less than a screenful.
• indent(1) is probably not too helpful.

The recursion wonderfully and magically takes care of iteration and backtracking. I could tell you how it works but then I would have to kill^Wrequest an NDA from you :-) Run it under a debugger with several inputs, it will be quite helpful and instructive. Handling of '?' is straightforward; for '' start out with 'foo' and 'foo' against 'foo'. How does it deal with sequences of adjacent `'? How could this be improved? If all else fails, recode the ?: operators with if/else and try again. For extra credit implement character classes like [a-z].

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