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.\" Copyright (c) 2011 Jukka Ruohonen
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.Dd September 18, 2011
.Dt SCALBN 3
.Os
.Sh NAME
.Nm scalbn ,
.Nm scalbnf ,
.Nm scalbnl
.Nd exponent using FLT_RADIX
.Sh LIBRARY
.Lb libm
.Sh SYNOPSIS
.In math.h
.Ft double
.Fn scalbn "double x" "int n"
.Ft float
.Fn scalbnf "float x" "int n"
.Ft long double
.Fn scalbnl "long double x" "int n"
.Sh DESCRIPTION
The
.Fn scalbn ,
.Fn scalbnf ,
and
.Fn scalbnl
functions compute
.Fa x
*
.Fa r^n ,
where
.Fa r
is the radix of the machine's floating point arithmetic, defined by the
.Dv FLT_RADIX
constant in
.In float.h .
The rationale is efficiency;
.Fa r^n
is not computed explicitly.
.Sh RETURN VALUES
As described above, upon successful completion, the described functions return
the exponent computed using
.Dv FLT_RADIX .
Otherwise the following may occur:
.Pp
.Bl -enum -offset indent
.It
When the result would cause an overflow, a range error occurs and
.Dv \*(Pm\*HHUGE_VAL ,
.Dv \*(Pm\*HHUGE_VALF ,
or
.Dv \*(Pm\*HHUGE_VALL
is returned according to the sign of
.Fa x
and the return type of the corresponding function.
.It
When the correct value would cause an underflow
and it is not representable, a range error occurs and
either 0.0 or an implementation-defined value is returned.
When an underflow occurs but the correct value is representable,
a range error occurs but the correct value is returned.
.It
If
.Fa x
is \*(Pm0 or \*(Pm\Inf,
.Fa x
is returned.
Likewise, if
.Fa n
is zero,
.Fa x
is returned.
If
.Fa x
is \*(Na, \*(Na is returned.
.El
.Sh SEE ALSO
.Xr exp 3 ,
.Xr frexp 3 ,
.Xr ldexp 3 ,
.Xr math 3
.Sh STANDARDS
The described functions conform to
.St -isoC-99 .