CODEWITHSUNDEEP
c++
H.L.Alumnus
H.L.Alumnus

Reputation: 69

About float to int

float x = 2.5;
int i = (int)x;

We all know the result is 2, but I want to know why we get this result, what is the theory and how the system work? Can it be explained using binary form (IEEE)?

Upvotes: 1

Views: 80

Answers (2)

R Sahu
R Sahu

Reputation: 206577

This is specified in the C++ Standard (Draft Standard N3337)

4.9 Floating-integral conversions

1 A prvalue of a floating point type can be converted to a prvalue of an integer type. The conversion truncates; that is, the fractional part is discarded. The behavior is undefined if the truncated value cannot be represented in the destination type. [ Note: If the destination type is bool, see 4.12. — end note ]

Upvotes: 1

Cheers and hth. - Alf
Cheers and hth. - Alf

Reputation: 145269

C++11 §4.9/1:

” The conversion truncates; that is, the fractional part is discarded. The behavior is undefined if the truncated value cannot be represented in the destination type.

That’s it, the theory of it: because the standard says so.

It's a reasonable language design choice but by no means the only possible reasonable choice.

Upvotes: 2

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