[uaxid.immutable]

# Annex E (informative) Conformance with UAX #31 [[uaxid]](./#uaxid)

## E.3 R2 Immutable identifiers [uaxid.immutable]

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/uax31.tex#L65)

An implementation may choose to guarantee that
the set of identifiers will never change
by fixing the set of code points allowed in identifiers forever[.](#1.sentence-1)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/uax31.tex#L70)

C++ does not choose to make this guarantee[.](#2.sentence-1)

As scripts are added to Unicode,
additional characters in those scripts may become available
for use in identifiers[.](#2.sentence-2)