[#BloombergLP-bdlb-BitMaskUtil-lt64]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdlb.adoc[bdlb]::xref:BloombergLP/bdlb/BitMaskUtil.adoc[BitMaskUtil]::lt64
:relfileprefix: ../../../
:mrdocs:

Return the unsigned integral value having all bits at positions less than the specified `index` set to 1, and all other bits set to 0. The behavior is undefined unless `0 <= index <= # of bits in result`.

== Synopsis

Declared in `<bdlb_bitmaskutil.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
static
uint64_t
lt64(int index);
----


[.small]#Created with https://www.mrdocs.com[MrDocs]#