这个 C 程序的输出我看不懂

Question

I am revising C again and was making some test programs. At one program I was checking a condition which was translating ino this condition.

#include <stdio.h>
int main()
{
if(0 <= 3000.000000 <= 2000.00){  //this is the condition
printf("3000 is less than 2000, whoa.. \n");
}
return 0;
}

The output is always this print string. I can't understand why.

PS

I am testing the middle value, ie 3000.000000 here, but it can be some variable.

Answer 1

The condition is parsed like this:

if((0 <= 3000.000000) <= 2000.00){ 

The first part, (0 <= 3000.000000) , is true, and evaluates to 1 in the comparison with 2000.00 . And 1 <= 2000.00 is true.

If you're trying to test whether a value a lies between two values b and c or is equal to either, then you need an expression along the lines of

(a >= b) && (a <= c)

Answer 2

You're getting caught by the fact that in C, booleans are integers: either 0 or 1 .

So that line is interpreted left-to-right: First 0 <= 3000 , which is true so it ends up as 1 . Then that value is fed into the next half, (1) <= 2000 , which is obviously true.

Answer 3

It will prints the string in printf.

Because the condition is static.

The 0 is always less than 30000.000000. For the next condition the output of the first condition returns 1. it checks using the 1.

The second condition checking is 1 <= 2000.00. This condition is also true.

So, only this prints the string.

Answer 4

第一个条件评估为 1 作为输出，并进一步检查 1<2000 这也是真的。所以，字符串被打印出来。