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#include <stdio.h>
#include <stdlib.h>
/*
example: 10 / 3
num denom quotient result
10 3 1 0
10 6 2 2
4 3 1 3
*/
/*
// working, let's simplify it.
int divide(int num, int denom) {
int result = 0, quotient = 1, newdenom;
fprintf(stderr, "\tdivide(%d, %d)\n", num, denom);
do {
fprintf(stderr, "outer loop\n");
newdenom = denom;
quotient = 1;
if(newdenom > num) {
fprintf(stderr, "%d > %d: quotient = 0;\n", newdenom, num);
quotient = 0;
num = 0;
// return result;
} else if(newdenom == num) {
fprintf(stderr, "%d == %d: quotient = 1;\n", newdenom, num);
quotient = 1;
num = 0;
// return ++result;
} else {
while(newdenom <= num) {
fprintf(stderr, "inner loop %d %d %d\n", num, newdenom, quotient);
newdenom <<= 1;
quotient <<= 1;
}
newdenom >>= 1;
num -= newdenom;
quotient >>= 1;
}
result += quotient;
fprintf(stderr, "num==%d, newdenom==%d, quotient==%d, result==%d\n", num, newdenom, quotient, result);
} while(num);
return result;
}
*/
int divide(int num, int denom) {
int result, quotient, newdenom, halfnum;
result = 0;
outerloop:
newdenom = denom;
quotient = 1;
if(newdenom < num)
goto innerprep;
if(newdenom == num)
goto innerprep;
quotient = 0;
num = 0;
goto addquot;
innerprep:
halfnum = num >> 1;
innerloop:
if(newdenom > halfnum)
goto innerdone;
newdenom <<= 1;
quotient <<= 1;
goto innerloop;
innerdone:
num -= newdenom;
addquot:
result += quotient;
if(num) goto outerloop;
return result;
}
/*
// working, but recursive, doesn't lend itself well to
// rewriting in asm.
int divide(int num, int denom) {
int quotient = 1, olddenom = denom;
fprintf(stderr, "\tdivide(%d, %d)\n", num, denom);
if(denom > num) return 0;
if(denom == num) return 1;
while(denom <= num) {
denom <<= 1;
quotient <<= 1;
fprintf(stderr, "num==%d, denom==%d, quotient==%d\n", num, denom, quotient);
}
num -= (denom >> 1);
return ((quotient >> 1) + divide(num, olddenom));
}
*/
int main(int argc, char **argv) {
int num = 100, denom = 10, result1, result2;
if(argc > 1) num = atoi(argv[1]);
if(argc > 2) denom = atoi(argv[2]);
result1 = num / denom;
result2 = divide(num, denom);
printf("%d / %d == %d\n", num, denom, result1);
printf("divide(%d, %d) == %d\n", num, denom, result2);
if(result1 == result2) {
puts("OK");
return 0;
}
puts("FAIL");
return 1;
}
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