當我得到 (j>1) 作為條件時，為什么我得到 1 作為答案？

Question

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>

double rand_double() {
    return ( ((double)rand())/ ((double)RAND_MAX) );
}

int main(){
    double i=rand_double();
    double j;
    do {
        i=(i*0.5);
        j=(1+i);
        printf("%lf\n", j);
    }
    while(j>1);
    return(0);
}

Answer 1

原因是您沒有顯示足夠的小數位。

所以1.000000是 output ，例如，該值為1.00000000000000022 ，即> 1 。

請嘗試更多小數位：

printf("%.17lf\n", j);

默認位數通常為double類型適用於大約 16-17 位有效數字。 修改程序 output：

1.00062562944425792
1.00031281472212896
1.00015640736106448
1.00007820368053224
1.00003910184026612
1.00001955092013306
1.00000977546006653
1.00000488773003338
1.00000244386501658
1.00000122193250829
1.00000061096625426
1.00000030548312702
1.00000015274156362
1.00000007637078170
1.00000003818539085
1.00000001909269542
1.00000000954634771
1.00000000477317386
1.00000000238658693
1.00000000119329346
1.00000000059664673
1.00000000029832337
1.00000000014916179
1.00000000007458079
1.00000000003729039
1.00000000001864531
1.00000000000932254
1.00000000000466138
1.00000000000233058
1.00000000000116529
1.00000000000058265
1.00000000000029132
1.00000000000014566
1.00000000000007283
1.00000000000003642
1.00000000000001821
1.00000000000000910
1.00000000000000466
1.00000000000000222
1.00000000000000111
1.00000000000000067
1.00000000000000022
1.00000000000000022
1.00000000000000000