Split a character string based on change of character: Difference between revisions

=={{header|Standard ML}}==

<lang sml>(*

* Head-Tail implementation of grouping

*)

fun group' ac nil = [ac]

| group' nil (y::ys) = group' [y] ys

| group' (x::ac) (y::ys) = if x=y then group' (y::x::ac) ys else (x::ac) :: group' [y] ys

fun group xs = group' nil xs

fun groupString str = String.concatWith ", " (map implode (group (explode str)))</lang>

{{out}}

<pre>- groupString "gHHH5YY++///\\";

val it = "g, HHH, 5, YY, ++, ///, \\" : string</pre>