document and provide string-split-lens

unstable/lens/main.rkt

@@ -6,6 +6,7 @@
          "arrow.rkt"
          "isomorphism.rkt"
          "mapper.rkt"
+         "string-split.rkt"
          )
 
 (provide (all-from-out "syntax.rkt"
@@ -14,4 +15,5 @@
                        "arrow.rkt"
                        "isomorphism.rkt"
                        "mapper.rkt"
+                       "string-split.rkt"
                        ))

unstable/lens/main.scrbl

@@ -15,3 +15,4 @@ this library being backwards-compatible.
 @include-section["arrow.scrbl"]
 @include-section["isomorphism.scrbl"]
 @include-section["mapper.scrbl"]
+@include-section["string-split.scrbl"]

unstable/lens/string-split.scrbl

@@ -0,0 +1,26 @@
+#lang scribble/manual
+
+@(require lens/doc-util/main)
+
+@title{Splitting Strings}
+
+@defmodule[unstable/lens/string-split]
+
+@defproc[(string-split-lens [sep (or/c string? char? regexp?)]) lens?]{
+Creates a lens that splits a string into multiple pieces like
+@racket[regexp-split] or @racket[string-split].
+@lenses-unstable-examples[
+  (lens-view (string-split-lens ",") "a,b,c")
+  (lens-set (string-split-lens ",") "a,b,c" '("1" "2" "3"))
+]
+Lenses created by @racket[string-split-lens] do not trim strings first, so that
+when viewing a target that either starts or ends with something matching
+@racket[sep], the view will include empty strings as the first or last element,
+which is consistant with @racket[regexp-split] or @racket[string-split] with
+@racket[#:trim? #f]. This is also more useful when using @racket[lens-set].
+@lenses-unstable-examples[
+  (lens-view (string-split-lens ",") ",b,c")
+  (lens-set (string-split-lens ",") ",b,c" '("a" "b" "c"))
+  (lens-view (string-split-lens ",") "a,b,c,")
+  (lens-set (string-split-lens ",") "a,b,c," '("a" "b" "c" "d"))
+]}