[#BloombergLP-bdldfp-DecimalImpUtil-logB-040]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdldfp.adoc[bdldfp]::xref:BloombergLP/bdldfp/DecimalImpUtil.adoc[DecimalImpUtil]::logB
:relfileprefix: ../../../
:mrdocs:

Return the FLT_RADIX‐based logarithm (i.e., base 10) of the absolute value of the specified `x`.

== Synopsis

Declared in `<bdldfp_decimalimputil.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
static
xref:BloombergLP/bdldfp/DecimalImpUtil/ValueType32.adoc[DecimalImpUtil::ValueType32]
logB(xref:BloombergLP/bdldfp/DecimalImpUtil/ValueType32.adoc[ValueType32] x);
----

== Description

Special value handling: * If `x` is +/‐0, ‐infinity is returned and the value of the macro `ERANGE` is stored into `errno`. * If `x` is 1, +0 is returned. * If `x` is +/‐infinity, +infinity is returned. * If `x` is quiet NaN, quiet NaN is returned. * If `x` is signaling NaN, quiet NaN is returned and the value of the macro `EDOM` is stored into `errno`.

Examples: `logB( 10.0)` ==> 1.0; `logB(‐100.0)` ==> 2.0


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