[英]C ternary operator branches evaluation?
I always assumed the ternary operator in C
did not evaluate the branch that failed the test.我一直假设C
中的三元运算符没有评估未通过测试的分支。 Why does it in this case?为什么在这种情况下呢? a
is less than b
so only c
should be assigned to 1
, d
should remain 2
. a
小于b
所以只有c
应该分配给1
, d
应该保持2
。 Thank your for tips and suggestions.感谢您的提示和建议。 I have compiled with both gcc-9 and clang.我用 gcc-9 和 clang 编译。
#include <stdio.h>
int main() {
int a = 42;
int b = 99;
int c = 0;
int d = 2;
// Both branches are evaluated?
a < b ? c, c = 1 : d, d = 1;
printf("c %d, d %d.\n", c, d);
// Prints c 1, d 1.
}
The comma operator has lower precedence than the conditional operator, so your expression is equivalent to:逗号运算符的优先级低于条件运算符,因此您的表达式等效于:
(a < b ? c, c = 1 : d), d = 1;
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