[#BloombergLP-balxml-NamespaceRegistry-lookup-0c]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/balxml.adoc[balxml]::xref:BloombergLP/balxml/NamespaceRegistry.adoc[NamespaceRegistry]::lookup
:relfileprefix: ../../../
:mrdocs:

Return the integer ID for the specified `namespaceUri`, or ‐1 if it is unregistered.

== Synopsis

Declared in `<balxml_namespaceregistry.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
lookup(std::string_view const& namespaceUri) const;
----

== Description

Note that not all negative return values correspond to unregistered namespaces. Preregistered namespaces always have negative IDs. (See "Preregistered Namespaces" in the `balxml_namespaceregistry` component‐level documentation.) Note that a return value of ‐1 can mean either an unregistered namespace or an empty URI string. This dual‐use of ‐1 is deliberate and simplifies error handling in most clients.

== Return Value

the integer ID for `namespaceUri`, or ‐1 if unregistered

== Parameters

[cols="1,4"]
|===
| Name| Description
| *namespaceUri*
| namespace URI to look up
|===


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