Update 1989 winning entries' README.md files
Format and typo fixes.
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@@ -1,23 +1,24 @@
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# Most algorithms in one program
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Merlyn LeRoy (Brian Westley)
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Starfire Consulting
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1026 Blair Ave.
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St. Paul, MN
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55104
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USA
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http://www.westley.org
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Merlyn LeRoy (Brian Westley)
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Starfire Consulting
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1026 Blair Ave.
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St. Paul, MN
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55104
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USA
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<http://www.westley.org>
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## To build:
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make all
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```sh
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make all
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```
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[Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) was able to get
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this to partially work with clang; clang requires that the second, third and
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fourth args to main() be `char **`. Only `westley.c` and `ver0.c` (see below) will
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compile with clang. It's possible to get ver1.c to compile too but this causes
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compile with clang. It's possible to get `ver1.c` to compile too but this causes
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problems with generating the output of the remaining files so we have opted, at
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least for now, to not do that, as it does not have to output just source code.
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He notes that the original source code sometimes segfaults with `ver2` which
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@@ -28,31 +29,32 @@ Thank you Cody for your help!
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## Try:
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./westley < westley.c > ver0.c
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./westley 1 < westley.c > ver1.c
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./westley 1 2 < westley.c > ver2.c
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./westley 1 2 3 < westley.c > ver3.c
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```sh
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./westley < westley.c > ver0.c
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./westley 1 < westley.c > ver1.c
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./westley 1 2 < westley.c > ver2.c
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./westley 1 2 3 < westley.c > ver3.c
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```
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Try compiling and running the 4 resulting programs. To compile try:
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make ver0
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make ver1
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make ver2
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make ver3
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```sh
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make ver0
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make ver1
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make ver2
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make ver3
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```
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## Judges notes:
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## Judges' remarks:
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There is a secret way to get ONE of the versions to print out
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"Hello, world!\n". Can you find how to do it?
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## Selected notes from the author:
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## Author's remarks:
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This is a filter. If it is run with no arguments, it copies
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stdin to stdout. With one argument, it ROT13's stdin to
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@@ -63,42 +65,44 @@ Also requires two's complement (I think).
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The source code will run if ROT13'ed and/or reversed, using a
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different algorithm for each version (hereafter referred to as
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ver0 (original), ver1 (ROT13), ver2 (reversed), and ver3
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`ver0` (original), `ver1` (ROT13), `ver2` (reversed), and `ver3`
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(ROT13 and reversed)).
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When compiling these versions, one needs to define 'trgpune'
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in the compile line (which the Makefile now has). Example:
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cc -Dtrgpune=putchar ver3.c -o ver3
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```sh
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cc -Dtrgpune=putchar ver3.c -o ver3
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```
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"trgpune" is the ROT13 of getchar(), so getchar() and putchar()
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`trgpune` is the ROT13 of `getchar()`, so `getchar()` and `putchar()`
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are exchanged in the ROT13 counterpart. It is easy to see that
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this is unavoidable. I must have a #define for a library
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this is unavoidable. I must have a `#define` for a library
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function; otherwise I would have an unidentified extern for the
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ROT13 version. If I then define this function, it won't link
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in the library version for the ORIGINAL code, since my
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definition will supersede the library function. Hence, the
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compiler option gives me putchar(), and allows me to use
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getchar(). I pass a dummy argument to getchar() to eliminate
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compiler option gives me `putchar()`, and allows me to use
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`getchar()`. I pass a dummy argument to `getchar()` to eliminate
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"variable number of args" from lint (unless it checks against
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the library). Otherwise, all versions lint reasonably (main
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returns random value & constant in conditional context [when I
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check for ROT13 version] is all it complains about).
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ver0 and ver1 use a range check and a calculation to do ROT13,
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while ver2 and ver3 use table lookup. All versions contain
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main() and it's ROT13 fn, znva(). ver0/ver1 [ver2/ver3] are
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`ver0` and `ver1` use a range check and a calculation to do ROT13,
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while `ver2` and `ver3` use table lookup. All versions contain
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`main()` and it's ROT13 fn, `znva()`. `ver0`/`ver1` [`ver2`/`ver3`] are
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(of course) syntactically identical, since the syntax is in the
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non-alphabetic characters. However, since one program starts
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at main() while it's ROT13 counterpart starts at znva(), znva()
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calls main (znva() is also used for output).
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at `main()` while it's ROT13 counterpart starts at `znva()`, `znva()`
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calls main (`znva()` is also used for output).
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All versions use recursion to work. If the program is NOT
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reversing it's output, it prints out the (possibly ROT13'd)
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character before recursing, otherwise it prints it out
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afterward (or doesn't recurse at all when EOF is reached).
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Since most of this code is identical, it is put into znva() and
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called with a first parameter of 0 as a flag (as "main()", it's
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Since most of this code is identical, it is put into `znva()` and
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called with a first parameter of 0 as a flag (as `main()`, it's
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first argument (argc) must be at least one).
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I can't use any flow control. If I used if(), I would have a
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@@ -106,45 +110,62 @@ function vs() to define in the ROT13 version. But a function
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called vs() turns into a function called if() in the original,
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so it can't be done. Therefore, I do:
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expr1 && expr2 && (expr3=etc);
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```c
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expr1 && expr2 && (expr3=etc);
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```
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which is the same as:
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if (expr1 && expr2) expr3=etc;
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```c
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if (expr1 && expr2) expr3=etc;
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```
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A/UX on the Macintosh doesn't get this right; it evaluates ALL
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expressions if they aren't in an assignment or conditional
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statement. This might warrant a warning, since other compilers
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may do this. I found MANY compilers botched:
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expr1 && (expr2,expr3);
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```c
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expr1 && (expr2,expr3);
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```
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expr2 was OFTEN evaluated even if expr1 was false. I removed
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`expr2` was OFTEN evaluated even if `expr1` was false. I removed
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such statements to make it more portable.
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The variable names are worth noting:
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'irk' and 'vex' are ROT13 pairs and are synonyms.
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'Near' and 'Arne' are ROT13 pairs and are anagrams.
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'NOON' and 'ABBA' are ROT13 pairs and are palindromes.
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'tang' and 'gnat' are both ROT13 and palindrome pairs!
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--
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'irk' and 'vex' are ROT13 pairs and are synonyms.
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'Near' and 'Arne' are ROT13 pairs and are anagrams.
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'NOON' and 'ABBA' are ROT13 pairs and are palindromes.
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'tang' and 'gnat' are both ROT13 and palindrome pairs!
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--
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Normally (!), a reversible C program is done thus:
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/**/ forward code /*/ edoc drawkcab /**/
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```c
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/**/ forward code /*/ edoc drawkcab /**/
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```
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If your compiler nests comments, it will get this wrong.
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However, I have made some bits of the code palindromic,
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(or different, but reversible) so it is more like:
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/**/forward/*//**/ palindromic /**//*/drawkcab/**/
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```c
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/**/forward/*//**/ palindromic /**//*/drawkcab/**/
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```
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The code can therefore be interlaced. There are eight
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such palindromic bits. You can find them within the
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`/*//**/ /**//*/` pairs.
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The body of the code of ver0 and ver1 is a large lumpy 'K' (for
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Kernighan); the code of ver2 and ver3 is a flat-topped and
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The body of the code of `ver0` and `ver1` is a large lumpy 'K' (for
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Kernighan); the code of `ver2` and `ver3` is a flat-topped and
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lumpier 'R' (for Ritchie). Judicious use of spaces and tabs
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helped here. It barely fits on an 80x24 screen. Squint. Note
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that the code must start with a blank line, or the reversed version
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