substring

[.]

Hi,

Why do we need substring [1]? We already have string-copy which looks
similar to me.
(These functions take different number of arguments, but string-copy
can handle this because it's more generic.)

Is this connected with compatability, convenience or something else?

[1] 
http://www.gnu.org/software/guile/manual/html_node/String-Selection.html#String-Selection

Thanks