CODEWITHSUNDEEP
c
radhika
radhika

Reputation: 29

What is the return type of this expression in C?

If i is an int variable and f is a float variable, what is the type of the conditional expression (i > 0 ? i : f)?

Consider any arbitrary value of i because I just want to know the type of the expression. I am not getting how can we check the type of this expression because if we store the result in an int variable, we get the output as integer and if the result is stored in a float variable, the output is float.

Question taken from K. N. King book.

Upvotes: 0

Views: 382

Answers (3)

Rorschach
Rorschach

Reputation: 60

#include <stdio.h>

int main(void)
{
   int i=0;
   double f=1.0;
   printf("%d\n",i>0?i:f);
   return 0;
}

gcc version 6.3.0, compile with -Wall

warning: format '%d' expects argument of type 'int', but argument 2 has type 'double' [-Wformat=]
  printf("%d\n",i>0?i:f);

so the type of (condition?int:float) is float

Upvotes: -3

bolov
bolov

Reputation: 75924

Getting inspired by Determining the type of an expression:

void test()
{
    int i = 0;
    float f = 0.;

    int ***a = i > 0 ? i : f;
}

error: initializing 'int ***' with an expression of incompatible type 'float'

int ***a = i > 0 ? i : f;
       ^   ~~~~~~~~~~~~~

So the type is float.

The printf method suggested is unreliable as in varargs float gets promoted to double.

As for the reasoning there is already another answer with quotes from the standard mentioning common type so I won't repeat it here.

Upvotes: 3

Acorn
Acorn

Reputation: 26194

In 6.5.15 Conditional operator, paragraph 4:

If both the second and third operands have arithmetic type, the result type that would be determined by the usual arithmetic conversions, were they applied to those two operands, is the type of the result.

And then in 6.3.1.8 Usual arithmetic conversions, paragraph 1:

Otherwise, if the corresponding real type of either operand is float, the other operand is converted, without change of type domain, to a type whose corresponding real type is float.

Therefore, the type of the expression is float.

Upvotes: 4

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