regexp_replace( , , , NULL ) returns null?

Is there any particular reason for this:

decibel@decina.local=# SELECT regexp_replace( 'a', 'a', 'b', null ) IS NULL;?column?
----------t
(1 row)

ISTM it’d be a lot better if it treated NULL flags the same as ‘’...
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Jim Nasby, Lead Data Architect   (512) 569-9461