string-fill!

[procedure] string-fill! string char

R5RS: Stores char in every element of the given string and returns an unspecified value.

R6RS: In R6RS, this procedure is moved to a library (rnrs mutable-strings (6)), which is not included in the composite library (rnrs (6)).

[procedure] string-fill! string char [start end]

SRFI-13 extends R5RS to take optional arguments.