Best Abuse of the C Preprocessor

xxxxxxxxxx

#include <stdio.h>

​

#define maxc (prs >> 16)

#define maxr (prs & 0xff00) >> 8

#define find (col > 1)

#define endb || (prs & 16) && X(0) || chpa || (eols, 0)

#define lnst doln ? 0 : (init, 0) || (prs & 128) && X(0)

#define L    endb) || 0 || (find ? 0 : (rrr++, rrc = 0)) || (lnst

#define X(p) (dfc++ && ((prs & 48) != 32 || rrc < maxc) && ++ccl && \

             (find ? (bat = bit, bit = but, but = p, ccl == col && \

             (ret = bat + bit + but) + 1) : (las = las * 2 + \

             (((main(ccl + 1, cro - 1) + main(ccl + 1, cro) + \

             main(ccl + 1, cro + 1) - p) | p) == 3), occ |= las & 1, \

             printf(" %c", "_O"[las & 1]), ccl == 2 && (sta |= (las & 3) << 6),\

             0)))

#define _    || (find || rrc++, 0) || X(0)

#define O    || (find || rrc++, 0) || X(1)

#define chpa (find && col > ccl && ((ret = bit + but) + 1))

#define eols (!find && (cro == 1 ? (sta |= occ << 3) : cro == 2 && \

             (sta |= occ << 2), sta |= (las & 3) << 4))

#define init (find ? (ret = bit = but = 0) : (ocp = occ, las = occ = 0, \

             printf("\nL")), dfc = (prs & 192) != 64, ccl = 0)

#define doln !(dfl++ && (((prs & 3) != 2) || rrr < maxr) && \

             (++cro == row || !find))

#define recu (col =- col, (ccl = find ? rcf : rcl), cro = rro, 0 _ || \

             (rrc >= maxc ? 0 : (find ? rcf = ccl : (rcl = ccl), \

             main(-col, row))))

#define addl (lnst || (rro = cro, find ? rcf = ccl : (rrc = 0, rcl = ccl), \

             0) || main(-col, row) || (ccl = rcl + 1, 0) endb)

#define outp (find || printf("\n\nGEN %d STAT %ld\nEND\n", ++gen, \

             (long)ccl << 16 | cro << 8 | (sta | occ | ocp << 1) ^ 0x66))

#define GEN  endb) || (prs & 1) && addl || (outp, 0)), ret)); } int gen =

#define STAT ;long prs =

#define END  ;

#define LIFE int bat, bit, but, las, gen, ret, rcl, rcf, rro, rrc, rrr, \

             occ, ocp, sta, dfc; long prs; main(int col, int row) { \

             int dfl = ((prs & 12) != 4), ccl = 0, cro = 0; return \

             col == 1 && printf("LIFE\n"), (col < 0 ? recu : \

             (((ret = 0) || (prs & 8) && addl || 0 && (0

​

#include "life.d"

引用元：https://www.ioccc.org/1993/dgibson.c

審査員・作者による説明：https://github.com/ioccc-src/winner/blob/main/1993/dgibson.hint

動作

ライフゲーム。life.dに初期盤面を入れておく。

$ cat life.d
LIFE

L _ _ _ _ _
L _ _ _ O _
L _ O _ O _
L _ _ O O _
L _ _ _ _ _

GEN 0 
END

1世代すすめる。

$ gcc -ansi dgibson.c -o dgibson

$ ./dgibson
LIFE

L _ _ _ _ _
L _ _ O _ _
L _ _ _ O O
L _ _ O O _
L _ _ _ _ _

GEN 1 STAT 329040
END

見ての通りこの出力は初期盤面と同じフォーマットになっているので、life.dを更新して再コンパイルするとさらに次の世代が求められる。

$ ./dgibson > life.d

$ gcc -ansi dgibson.c -o dgibson

$ ./dgibson
LIFE

L _ _ _ _ _
L _ _ O _ _
L _ _ _ O _
L _ O O O _
L _ _ _ _ _

GEN 2 STAT 328960
END

解説

dgibson.cの最後で#include "life.d"としているとおり、この盤面のフォーマットはdgibson.cで定義されたマクロで展開することで有効なCコードとなる。C言語での組み込みDSLと言える。

こんな大きいのも動くので良い。ビルドにちょっと時間がかかるが、実行は一瞬。

$ time gcc -ansi dgibson.c -o dgibson

real    0m2.400s
user    0m2.179s
sys     0m0.211s

$ ./dgibson
LIFE

L _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
L _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ O _ O _ _ _ _ _ _ _ _ _ _
L _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ O _ _ O _ _ _ _ _ _ _ _ _
L _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ O O _ _ _ _ _ _ _ _
L _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ O O O _ _ _ O O O _ _ _ _ _ O _ _ _ _ O _ _ _ _ _ _ _
L _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ O _ _ O _ _ _ O _ _ O _ _ _ _ O _ O O O O O _ _ _ _ _ _
L _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ O _ _ _ O _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ O O _ _ _
L _ _ _ _ _ _ _ _ _ _ O O _ _ _ _ _ _ _ _ _ _ O _ _ _ O _ _ _ _ _ _ _ _ _ _ _ O O O _ _ _ O _ _
L _ _ _ _ _ _ _ _ _ O _ _ _ _ _ _ _ _ _ _ _ _ O _ _ _ O _ _ _ _ _ _ _ _ _ _ _ _ _ _ O _ _ _ O _
L _ _ _ _ _ _ _ _ O O _ _ O _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ O _ _ _ _ _ O _
L _ _ _ _ _ _ _ O _ _ _ _ O _ _ _ _ _ _ _ O O O _ _ _ O O O _ _ _ _ _ _ _ _ _ _ O _ _ O _ _ O _
L _ _ _ _ _ _ O O O O O _ _ _ _ _ _ _ _ _ _ O _ _ _ _ _ O _ _ _ _ _ _ _ _ O _ O O _ _ O _ O _ _
L _ _ _ O O _ _ _ _ _ O O _ _ _ _ O _ _ _ _ O O O O O O O _ _ _ _ _ _ _ _ O _ _ _ _ _ _ _ _ _ _
L _ _ O _ _ _ O O O _ _ O _ _ O O O _ _ _ O _ _ _ _ _ _ _ O _ _ _ _ _ _ _ _ _ _ _ _ _ _ O O O _
L _ O _ _ _ O _ _ _ _ _ O O _ O O _ _ _ O O O O O O O O O O O _ _ _ _ _ _ _ _ _ _ _ _ _ _ O O _
L _ O _ _ _ _ _ O _ _ _ O _ _ _ O _ _ O _ _ _ _ _ _ _ _ _ _ _ O _ _ _ _ _ _ _ _ _ _ _ _ O O O _
L _ O _ _ O _ _ O _ _ _ _ _ O O O _ O O O O O O O O O O O O O O _ _ _ _ _ O _ _ _ _ _ _ _ _ _ _
L _ _ O _ O _ _ O O _ O _ _ O O _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ O O _ _ O _ O O _ _ O _ O _ _
L _ _ _ _ _ _ _ _ _ _ O _ _ _ _ _ O O O O O O O O O O O O O O _ O O O _ _ _ _ _ O _ _ O _ _ O _
L _ O O O _ _ _ _ _ _ _ _ _ _ _ _ O _ _ _ _ _ _ _ _ _ _ _ O _ _ O _ _ _ O _ _ _ O _ _ _ _ _ O _
L _ O O _ _ _ _ _ _ _ _ _ _ _ _ _ _ O O O O O O O O O O O _ _ _ O O _ O O _ _ _ _ _ O _ _ _ O _
L _ O O O _ _ _ _ _ _ _ _ _ _ _ _ _ _ O _ _ _ _ _ _ _ O _ _ _ O O O _ _ O _ _ O O O _ _ _ O _ _
L _ _ _ _ _ _ _ _ _ _ O _ _ _ _ _ _ _ _ O O O O O O O _ _ _ _ O _ _ _ _ O O _ _ _ _ _ O O _ _ _
L _ _ O _ O _ _ O O _ O _ _ _ _ _ _ _ _ O _ _ _ _ _ O _ _ _ _ _ _ _ _ _ _ O O O O O _ _ _ _ _ _
L _ O _ _ O _ _ O _ _ _ _ _ _ _ _ _ _ O O O _ _ _ O O O _ _ _ _ _ _ _ O _ _ _ _ O _ _ _ _ _ _ _
L _ O _ _ _ _ _ O _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ O _ _ O O _ _ _ _ _ _ _ _
L _ O _ _ _ O _ _ _ _ _ _ _ _ _ _ _ _ _ _ O _ _ _ O _ _ _ _ _ _ _ _ _ _ _ _ O _ _ _ _ _ _ _ _ _
L _ _ O _ _ _ O O O _ _ _ _ _ _ _ _ _ _ _ O _ _ _ O _ _ _ _ _ _ _ _ _ _ O O _ _ _ _ _ _ _ _ _ _
L _ _ _ O O _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ O _ _ _ O _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
L _ _ _ _ _ _ O O O O O _ O _ _ _ _ O _ _ O _ _ _ O _ _ O _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
L _ _ _ _ _ _ _ O _ _ _ _ O _ _ _ _ _ O O O _ _ _ O O O _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
L _ _ _ _ _ _ _ _ O O _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
L _ _ _ _ _ _ _ _ _ O _ _ O _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
L _ _ _ _ _ _ _ _ _ _ O _ O _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
L _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

GEN 2 STAT 3089152
END