[#BloombergLP-bslfmt-FormatterIntegralBase-formatPrefix]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslfmt.adoc[bslfmt]::xref:BloombergLP/bslfmt/FormatterIntegralBase.adoc[FormatterIntegralBase]::formatPrefix
:relfileprefix: ../../../
:mrdocs:

Write the output prefix for `value` into `prefixStorage`.

== Synopsis

Declared in `<bslfmt_formatterintegralbase.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class t_ACTUAL_VALUE_TYPE>
char*
formatPrefix(
    char* prefixStorage,
    int storageSize,
    t_ACTUAL_VALUE_TYPE value) const;
----

== Description

Create the prefix for output of the specified `value` and write it into the character buffer starting at the specified `prefixStorage` and having the specified `storageSize`. Return the address one past the last character. Throw `bsl::format_error` if parsed format specification is intended for non‐integer type.

== Return Value

address one past the last character written

== Parameters

[cols="1,4"]
|===
| Name| Description
| *prefixStorage*
| buffer that receives the prefix characters
| *storageSize*
| size of `prefixStorage` in characters
| *value*
| value whose format prefix is produced
|===


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