gcc makes it possible to code this RPN interpreter more compactly than C89..C11
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//RPN calculator: E:EEf|n f:[+-*/] n:[0-9] typedef int I;typedef long J;typedef char C,*S;typedef J(*F)(J*);I printf(S,...);I(*O)(S,...)=printf; #define R return #define W(x,y...) while(x){y;} #define K(m) m(+)m(-)m(*)m(/) #define L(o) ""#o #define M(o) ({J _f(J*x){R x[0] o x[1];}_f;}), I main(I c,S*v) {if(c!=2)R O("use: %s 12+3-\n",*v); J s[99],*t=s;;J push(J x){R *t++=x;}J*pop(I n){R t-=n;}J jsc(S s,C c){S t=s;W(*t&&c!=*t,t++)R t-s;} C o[]=K(L);F f[]={K(M)0};S e=v[1];W(*e,push(*e>47?*e-'0':f[jsc(o,*e)](pop(2))),e++)R O("%ld\n",*pop(1)); } |