CODEWITHSUNDEEP
c++c++14autotype-deduction
qdii
qdii

Reputation: 12953

How does the compiler know which type to return

This article says:

If I write a line of code like this inside a function: return 1.4, It is obvious to both me and the compiler that the function is returning a double.

It is not obvious to me: the return type could be a float, a double, or a long double. How does the compiler choose between the 3 types?

Upvotes: 4

Views: 172

Answers (5)

Humam Helfawi
Humam Helfawi

Reputation: 20264

No, 1.4 is a double. float is written as 1.4f

75         // int
75u        // unsigned int
75l        // long
75ul       // unsigned long 
75lu       // unsigned long

3.14159L   // long double
6.02e23f   // float

Source

Upvotes: 3

ammar26
ammar26

Reputation: 1612

1.4 is double here, any simple decimal point number is double.

float will be 1.4f

long double will be 1.4L

1.4  // double
1.4f // float
1.4L // long double

Upvotes: 1

Baum mit Augen
Baum mit Augen

Reputation: 50043

I guess you are asking about auto return type deduction, otherwise the return type is whatever you declare it to be.

The answer is straight forward: The literal 1.4 has type double, not float or long double, so double will be deduced. Easy as that.

Upvotes: 2

Mats Petersson
Mats Petersson

Reputation: 129314

Because 1.4 (or any other floating point number) is double. To make it float you need to write 1.4f, and long double is 1.4L.

Upvotes: 1

cadaniluk
cadaniluk

Reputation: 15229

1.4 is a double literal as opposed to the float literal 1.4f and the long double literal 1.4l.

Therefore, the compiler can deduce the type unambiguously.

Upvotes: 3

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