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

Return the integer ID for the specified `namespaceUri` or ‐1 if the namespace has not been registered. 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.

== Synopsis

Declared in `<balxml_namespaceregistry.h>`

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


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