Merge pull request #241 from ianthehenry/document-split

document the (split) PEG special

Author: bakpakin

content/docs/peg.mdz

@@ -218,7 +218,17 @@ compiled to bytecode).
              @code`patt` cannot match more than @code`window-patt`; it will
              see end-of-input at the end of the substring matched by
              @code`window-patt`. If @code`patt` also succeeds, @code`sub` will
-             advance to the end of what @code`window-patt` matched. }}}
+             advance to the end of what @code`window-patt` matched. }}
+
+    @tr{@td{@code`(split separator-patt patt)` }
+        @td{ Split the remaining input by @code`separator-patt`, and execute
+             @code`patt` on each substring. @code`patt` will execute with its
+             input constrained to the next instance of @code`separator-patt`,
+             as if narrowed by @code`(sub (to separator-patt) ...)`.
+             @code`split` will continue to match separators and patterns until
+             it reaches the end of the input; if you don't want to match to the
+             end of the input you should first narrow it with
+             @code`(sub ... (split ...))`. }}}
 
 PEGs try to match an input text with a pattern in a greedy manner.  This means
 that if a rule fails to match, that rule will fail and not try again. The only