CODEWITHSUNDEEP
c
Tristan
Tristan

Reputation: 2088

Why does float divided by an integer return a float

I am learning C. I was wondering why you get a float, even if one of your variables is an int. 

float x = 5.0;
int y = 2;

float result = x / y;

My guess would be that result would be 2.00000. But it does return a float (2.500000)

I think it would be 2.000000 because if you divide 2 ints that is the result. And I would think that if you use an int and a float it would pick the least precise value.

Upvotes: 0

Views: 10368

Answers (6)

Shon
Shon

Reputation: 486

The result of the code is a float and therefore it will produce a float. When you devide an int by anf int it will return 2.5 but the result being an int truncates the result to be 2

Upvotes: 0

Matteo Italia
Matteo Italia

Reputation: 126937

And I would think that if you use an int and a float it would pick the least precise value.

That's exactly the opposite; the general rule is that before performing any arithmetic operation both operands are promoted to the "most powerful" type of the two involved in the operation.

The "most powerful" type is determined according to the rules that the standard calls "Usual arithmetic conversions" (C99, §6.3.1.8), which essentially say that long double > double > float > all integral types; if an expression involves only integral types, some other rules kick in that are a bit more lengthy to describe (at §6.3.1.1).

Now, in your case you have an int and a float, the "best" type is float and thus the int is promoted to float before performing the division.

Upvotes: 1

Leandros
Leandros

Reputation: 16825

Because of C's Usual arithmetic conversions.

Quoting the ANSI C standard § 3.2.1.5 Usual arithmetic conversions:

Many binary operators that expect operands of arithmetic type cause conversions and yield result types in a similar way. The purpose is to yield a common type, which is also the type of the result. This pattern is called the usual arithmetic conversions: First, if either operand has type long double, the other operand is converted to long double . [...] Otherwise, if either operand has type float, the other operand is converted to float.

Emphasis mine.

Upvotes: 4

Ario Aliabadi
Ario Aliabadi

Reputation: 90

First of all, result is a float, so it can hold decimal values.

Secondly, one of the operands x, and y is a float, so the returned value is a float. This holds for addition, multiplication and subtraction also.

Upvotes: 0

ForceBru
ForceBru

Reputation: 44906

If one of the operands in you division is a float and the other one is a whole number (int, long, etc), your result's gonna be floating-point.

This means, this will be a floating-point division: if you divide 5 by 2, you get 2.5 as expected.

Upvotes: 0

August Karlstrom
August Karlstrom

Reputation: 11377

The operator / only performs integer division if both operands are integers.

Upvotes: 2

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