printf不支持%lf

#include <stdio.h>

int square137(int n);

void p137() {
    double x = 3.0;
    int y = (int)x;
    printf("Square of %f is %d
", x, square137(y));
}

int square137(int n) {
    return n * n;
}

如果你吧%f改为%lf的话，输出就会出乎你的意料，试试便知