add `whitespace?` to unstable/typography

pollen/private/ts.rktd

@@ -1 +1 @@
-1455307528
+1455676575

pollen/scribblings/typography.scrbl

@@ -69,4 +69,36 @@ Be warned: there are many edge cases this function does not handle well.
 @examples[#:eval my-eval
 (code:comment @#,t{Argh: this edge case is not handled properly})
 (wrap-hanging-quotes '(p "“" (em "What?") "We need to hang quotes?”"))
+]
+
+@defproc[
+(whitespace?
+[v any/c])
+boolean?]
+A predicate that returns @racket[#t] for any stringlike @racket[_v] that's entirely whitespace, but also the empty string, as well as lists and vectors that are made only of @racket[whitespace?] members. Following the @racket[regexp-match] convention, @racket[whitespace?] does not return @racket[#t] for a nonbreaking space. If you prefer that behavior, use @racket[whitespace/nbsp?]. 
+
+
+@examples[#:eval my-eval
+(whitespace? "\n\n   ")
+(whitespace? (string->symbol "\n\n   "))
+(whitespace? "")
+(whitespace? '("" "  " "\n\n\n" " \n"))
+(define nonbreaking-space (format "~a" #\u00A0))
+(whitespace? nonbreaking-space)
+]
+
+@defproc[
+(whitespace/nbsp?
+[v any/c])
+boolean?]
+Like @racket[whitespace?], but also returns @racket[#t] for nonbreaking spaces.
+
+
+@examples[#:eval my-eval
+(whitespace/nbsp? "\n\n   ")
+(whitespace/nbsp? (string->symbol "\n\n   "))
+(whitespace/nbsp? "")
+(whitespace/nbsp? '("" "  " "\n\n\n" " \n"))
+(define nonbreaking-space (format "~a" #\u00A0))
+(whitespace/nbsp? nonbreaking-space)
 ]

pollen/unstable/typography.rkt

@@ -1,5 +1,7 @@
 #lang racket/base
-(require racket/list sugar/define sugar/test txexpr racket/match sugar/unstable/container sugar/coerce sugar/unstable/len racket/string "../private/to-string.rkt" )
+(require racket/list sugar/define sugar/test txexpr racket/match sugar/unstable/container sugar/coerce sugar/unstable/len  "../private/whitespace.rkt")
+
+(provide whitespace? whitespace/nbsp?)
 
 (define (make-replacer query+replacement)
   (let ([queries (map car query+replacement)]