1996 fixes and updates
Update the README.md files - at least with those not in a previous commit. The updates mostly include formatting (make them markdown) but probably also typos here and there. More probably has to be done with these files. The 1996/august/.gitignore was updated as well with a file that is generated by one of the suggested commands.
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@@ -12,119 +12,131 @@
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make all
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### To run
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## To run:
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./schweikh2
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## Judges' comments
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The program accepts up to 4 parameters:
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Also try:
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0. The number of operators in the expression [default: 9]
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1. The value of the first operand [default: 1]
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2. The (possibly negative) increment to the next operand [default: 1]
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3. The goal value or 0/0 [default: 42]
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## Try:
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./schweikh2 15 1 0 0/0
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The program accepts up to 4 parameters:
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What happens if you pass only three parameters like the below?
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1) The number of operators in the expression [default: 9]
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./schweikh2 15 1 0
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2) The value of the first operand [default: 1]
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## Judges' comments:
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3) The (possibly negative) increment to the next operand [default: 1]
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4) The goal value or 0/0 [default: 42]
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The original program, with only slight obfuscations, may be found
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in hunni.c. The perl script, obfuscates it appropriately:
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The original program, with only slight obfuscations, may be found
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in `hunni.c`. The perl script, obfuscates it appropriately:
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perl ./hunni.pl < hunni.c
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This entry was another crowd pleaser at the IOCCC BOF.
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This entry was another crowd pleaser at the IOCCC BOF.
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## Author's comments
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## Author's comments:
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Note: the source must be viewed with tabstop 8. To appreciate the
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beauty have your eyes half closed.
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Note: the source must be viewed with tabstop 8. To appreciate the
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beauty have your eyes half closed.
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Why I think this program is obfuscated:
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### Why I think this program is obfuscated:
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C is a free format language. It is therefore a question of style how
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variables, operators, declarations, functions and syntactic elements
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like braces and parentheses are grouped together. As a rule of thumb,
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I put spaces around operators, after opening braces and before closing
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braces. I have generalized this rule by putting whitespace after *any*
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non-white space character (with the exception of preprocessor directives).
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There are no recognizable keywords anymore. There are no recognizable
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string literals any more. The main function is invisible. All operators
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longer than one character have gone. They have been replaced by macro
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calls with quite a number of arguments. The keys are the token pasting
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and stringizing macros e and O. The "arcane rules of token pasting"
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[K&R2] are used up to three levels, H(O,r)R(O,r)! which is needed to make
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one 8-character token from 8 characters ('unsigned'). BTW, C has no 9 or
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more character reserved words, so a fourth level is only required if
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you intend to generate object names from 9 or more components. The final
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round even swaps the tokens, so all keywords must be spelled backwards
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(sort of, can you spot printf in the P macro?).
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C is a free format language. It is therefore a question of style how
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variables, operators, declarations, functions and syntactic elements
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like braces and parentheses are grouped together. As a rule of thumb,
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I put spaces around operators, after opening braces and before closing
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braces. I have generalized this rule by putting whitespace after *any*
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non-white space character (with the exception of preprocessor directives).
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There are no recognizable keywords anymore. There are no recognizable
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string literals any more. The main function is invisible. All operators
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longer than one character have gone. They have been replaced by macro
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calls with quite a number of arguments. The keys are the token pasting
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and stringizing macros e and O. The "arcane rules of token pasting"
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[K&R2] are used up to three levels, `H(O,r)R(O,r)` (!) which is needed to make
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one 8-character token from 8 characters ('unsigned'). BTW, C has no 9 or
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more character reserved words, so a fourth level is only required if
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you intend to generate object names from 9 or more components. The final
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round even swaps the tokens, so all keywords must be spelled backwards
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(sort of, can you spot printf in the P macro?).
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Try to indent the source. The unbalanced parentheses confuse Solaris'
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indent to the max (although the result does compile):
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Try to indent the source. The unbalanced parentheses confuse Solaris'
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indent to the max (although the result does compile):
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Looking at the indented source is even *less* fun, because the nice
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diamond pattern has been replaced by something that looks like, uhm,
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modem noise.
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Looking at the indented source is even *less* fun, because the nice
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diamond pattern has been replaced by something that looks like, uhm,
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modem noise.
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Lint the source. It's clean. How obfuscated...
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Lint the source. It's clean. How obfuscated...
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What's the exit status? The program exits with J - 1 where J is the
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return value from several non-void functions (needed to shut up
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lint). The last assignment is J = printf ("%c", 10); so the exit
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status is 0 unless the last printf failed, which is even a *useful*
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status. A further obfuscation is the use of 10 instead of '\n'.
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'\n' can not be constructed by token pasting, AFAIK. That's why schweikh2
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is likely to produce occasional garbage on non-ASCII execution character
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set systems.
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What's the exit status? The program exits with J - 1 where J is the
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return value from several non-void functions (needed to shut up
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lint). The last assignment is J = printf ("%c", 10); so the exit
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status is 0 unless the last printf failed, which is even a *useful*
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status. A further obfuscation is the use of 10 instead of '\n'.
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'\n' can not be constructed by token pasting, AFAIK. That's why `schweikh2`
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is likely to produce occasional garbage on non-ASCII execution character
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set systems.
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What this program does:
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-----------------------
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The program is an expression evaluator for a limited class of
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expressions. Known operators are + - * /, operands are real numbers
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(integers or fractions). The operands are restricted in that they must
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differ by a constant value, for example 1 + 2 * 3 / 4 - 5. For any
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combination of operators the expression is evaluated and compared to a
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goal value. If they compare equal the expression is printed. If the goal
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value is specified as 0/0 all expressions and results are printed. For
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any fraction, the numerator and denominator are divided by their
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greatest common divisor.
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What this program does:
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-----------------------
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The program accepts up to 4 parameters:
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1) The number of operators in the expression [default: 9]
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2) The value of the first operand [1]
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3) The (possibly negative) increment to the next operand [1]
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4) The goal value or 0/0 [42]
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The program is an expression evaluator for a limited class of
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expressions. Known operators are + - * /, operands are real numbers
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(integers or fractions). The operands are restricted in that they must
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differ by a constant value, for example 1 + 2 * 3 / 4 - 5. For any
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combination of operators the expression is evaluated and compared to a
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goal value. If they compare equal the expression is printed. If the goal
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value is specified as 0/0 all expressions and results are printed. For
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any fraction, the numerator and denominator are divided by their
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greatest common divisor.
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On ANSI/ISO C conformant systems (where long is at least 32 bits)
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overflow will occur in the default case (first operand 1, increment 1)
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only for more than 11 operators. Because a bit mask is used that needs
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twice the number of operands in bits (plus a sentinel value) on those
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systems the first parameter must not exceed 15.
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The program accepts up to 4 parameters:
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1) The number of operators in the expression [default: 9]
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2) The value of the first operand [1]
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3) The (possibly negative) increment to the next operand [1]
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4) The goal value or 0/0 [42]
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If long is at least 64 bits overflow will occur for more than 19
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operators but you will probably wait quite some time for every of the
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4^19 = 274,877,906,944 combinations to be evaluated... While I'm at it,
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on a 50 MHz sparc, 4^11 expressions are evaluated in about 3 cpu
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minutes (gcc -O3).
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On ANSI/ISO C conformant systems (where long is at least 32 bits)
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overflow will occur in the default case (first operand 1, increment 1)
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only for more than 11 operators. Because a bit mask is used that needs
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twice the number of operands in bits (plus a sentinel value) on those
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systems the first parameter must not exceed 15.
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Sample arguments:
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-----------------
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$ schweikh2 6
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$ schweikh2 7 0
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$ schweikh2 7 7 0
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$ schweikh2 8 9 -1 -67/21
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$ schweikh2 8 2 2/5 -98/25
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$ schweikh2 2 1/0 1 1/0
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If long is at least 64 bits overflow will occur for more than 19
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operators but you will probably wait quite some time for every of the
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4^19 = 274,877,906,944 combinations to be evaluated... While I'm at it,
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on a 50 MHz sparc, 4^11 expressions are evaluated in about 3 cpu
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minutes (gcc -O3).
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Sample arguments:
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-----------------
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$ ./schweikh2 6
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$ ./schweikh2 7 0
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$ ./schweikh2 7 7 0
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$ ./schweikh2 8 9 -1 -67/21
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$ ./schweikh2 8 2 2/5 -98/25
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$ ./schweikh2 2 1/0 1 1/0
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Miscellaneous
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-------------
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The diamond pattern can be continued without a break.
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For a nice printout try this on your Bourne compatible shell:
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% while :; do grep -v '#' schweikh2.c; done
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Miscellaneous
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-------------
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The diamond pattern can be continued without a break.
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For a nice printout try this on your Bourne compatible shell
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% while :; do grep -v '#' schweikh2.c; done
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