Confusing C code, does someone explain this to me?

Question

The order of evaluation is important, so what is called non-referential transparency?

int i = 1;
int counter(){
     i = i + 1;
     return i;
}
int foo(int i, int j){
    return i*2 + 3*j;
}
int main(){
   printf("%d", foo(counter(), counter()));
}

Answer 1

I assume that you can keep in mind that the order of evaluation of function parameters is not standardized in C. Since it counter()returns a different result for each call, and the result foo(2, 3)is different from the result foo(3, 2), compiling and executing this code can give different results on different platforms.

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Answer 4

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Answer 5

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#include <stdio.h>

int i = 1;

int counter1(){
     i = i * 3;
     printf( "counter1()\n");
     return i;
}

int counter2(){
     i = i * 5;
     printf( "counter2()\n");
     return i;
}

int foo(int i, int j){
    return i + j;
}

int main(){
   int x;
   for (x=0; x<2; ++x) {
       printf("%d\n", foo(counter1(), counter2()));
   }

   return 0;
}

, ( ):

1:

counter1()
counter2()
18
counter1()
counter2()
270

2:

counter1()
counter2()
18
counter2()
counter1()
300

3:

counter2()
counter1()
20
counter2()
counter1()
300

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Answer 6

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Answer 7

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Answer 8

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(there are many ways to make a link function opaque, they are more common)

Here, subsequent calls to counter () lead to different values, so they are opaque by reference.