c++ basic question please resolve

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what is difference between 0.0 and 0.00 and 0.0f and 0.000f?

Posted 4-Sep-13 19:32pm

nilesh_code_project

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Sergey Alexandrovich Kryukov · Answer 1 · 2013-09-04T19:39:00

Solution 1

~~No difference.~~You apparently need to lean about the syntax for literal and how floating-point data types work: http://en.wikipedia.org/wiki/Floating_point[^].

[EDIT]

The literal without "f" is implementation dependent in C++, can be double of float, but the ones with "f" mean single-precision floating-point literal. All values are identical and represent zero real number.

(Credit to the comment by Ron Beyer below.)

—SA

Posted 4-Sep-13 19:39pm

Sergey Alexandrovich Kryukov

Updated 4-Sep-13 20:25pm

v6

Comments

Ron Beyer 5-Sep-13 1:48am

Almost :) At least with MSVCPP compiler 0.0 is a double and 0.0f is a float. See this post. This is pretty compiler and platform specific so it doesn't behave the same way on all of them, it may be equal or different.

Sergey Alexandrovich Kryukov 5-Sep-13 1:57am

Oops! I forgot it's C++ and used the .NET rule for floating-point, which is float type if no "f" or "d" postfix is used (I think double by default would be better). I fixed the answer and credited your comment. Thank you.
—SA

Ron Beyer 5-Sep-13 1:58am

Almost there, even in .NET just typing 0.0 is a double, 0.0f is a float. Try it out (I just did to verify). I get an invalid cast error and a red underline when I write float f = 0.0;

Sergey Alexandrovich Kryukov 5-Sep-13 2:17am

Oh bother, that's right; I messed up things. (After I saw this error for the first time, the idea to write without proper suffix never came to my mind.)
Thank you, I fixed again.
—SA

Ron Beyer 5-Sep-13 2:20am

5'd for all the effort (despite getting my name wrong LOL)

Sergey Alexandrovich Kryukov 5-Sep-13 2:26am

Thank you and sorry. I could not possibly forget your name, just time to have some sleep.
(Sigh...) Fixed again.
—SA

Ron Beyer 5-Sep-13 2:31am

:)

H.Brydon 6-Sep-13 17:19pm

Still still almost almost :-) :-)
It is not dependent on compiler or platform. This is defined in the C standard, and brought forward to C++ and beyond. It is common for all compliant compilers and platforms.

There is no difference (to generated code or internal representation between values on each of the following lines:
0. 0.0 0.000 00.0000
0.f 0.0f 0.0F 0.000f 00.000F
The first line represents a double zero, and the second line, each represents a float zero.

Sergey Alexandrovich Kryukov 6-Sep-13 21:27pm

Ah, thank you. That's why I hate to use literal without suffix, even when it is not formally required.
By the way, I don't like that approach at all. In Ada, there is a concept of "generic integer", "generic floating point literal", and so on. Such literal has the meaning defined by the actual type of the object being initialized, as soon as the literal can be interpreted as the correct value (in correct range, etc.) for the declared type.
—SA

Myung-Joo · Answer 2 · 2013-09-04T20:34:00

Solution 2

i know... "0.0 and 0.00" means double Type
i know... "0.0f and 0.000f" means float Type

for example,

C++

float a = 0.0;   // float <= double
float b = 0.00;   // float <= double
double c = 0.0f;   // double <= float 
double d = 0.00f;   // double <= float

Posted 4-Sep-13 20:34pm

Myung-Joo