Purpose of a ".f" appended to a number?
Without the .f
the number gets interpreted as an integer, hence 1/3
is (int)1/(int)3
=> (int)0
instead of the desired (float)0.333333
. The .f
tells the compiler to interpret the literal as a floating point number of type float. There are other such constructs such as for example 0UL
which means a (unsigned long)0
, whereas a plain 0
would be an (int)0
.
The .f
is actually two components, the .
which indicates that the literal is a floating point number rather than an integer, and the f
suffix which tells the compiler the literal should be of type float rather than the default double type used for floating point literals.
Disclaimer; the "cast construct" used in the above explanation is not an actual cast, but just a way to indicate the type of the literal.
If you want to know all about literals and the suffixes you can use in them, you can read the C++ standard, (1997 draft, C++11 draft, C++14 draft, C++17 draft) or alternatively, have a look at a decent textbook, such as Stroustrup's The C++ Programming Language.
As an aside, in your example (float)1/3
the literals 1
and 3
are actually integers, but the 1 is first cast to a float by your cast, then subsequently the 3 gets implicitly cast to a float because it is a righthand operand of a floating point operator. (The operator is floating point because its lefthand operand is floating point.)
3.
is equivalent to 3.0
, it's a double.
f
following a number literal makes it a float.