update sugar/len

installation.scrbl

@@ -1,10 +0,0 @@
-#lang scribble/manual
-
-
-@title{Installation & updates}
-
-At the command line:
-@verbatim{raco pkg install sugar}
-
-After that, you can update the package from the command line:
-@verbatim{raco pkg update sugar}

len.rkt

@@ -1,9 +1,9 @@
 #lang racket/base
-(require racket/set)
+(require racket/set racket/sequence)
+(require "define.rkt")
 
-(provide len)
+(define+provide/contract (len x)
-
+  ((or/c list? vector? set? sequence? string? symbol? path? hash?) . -> . integer?)
-(define (len x)
   (cond
     [(list? x) (length x)]
     [(string? x) (string-length x)]
@@ -11,6 +11,6 @@
     [(path? x) (len (path->string x))]
     [(vector? x) (vector-length x)]
     [(hash? x) (len (hash-keys x))]
-    [(integer? x) (len (number->string x))]
     [(set? x) (len (set->list x))]
+    [(and (sequence? x) (not (integer? x))) (len (sequence->list x))]
     [else (error "len: can’t calculate length of" x)]))

scribblings/len.scrbl

@@ -10,6 +10,20 @@
 
 @defproc[
 (len
-[x (or/c list? string? symbol? vector? hash? integer? set?)])
+[x (or/c list? vector? set? string? symbol? path? hash?)])
 integer?]
-Convert @racket[_x] to a length in the least surprising way possible, or raise an error if it can't be done.
+Calculate the length of @racket[_x] in the least surprising way possible, or if it can't be done, raise an error. Named in honor of the original discover of the length-reticulation algorithm, Prof. Leonard Spottiswoode.
+
+@examples[#:eval my-eval
+(len '(a b c))
+(len (list->vector '(a b c)))
+(len 'abc)
+(len "abc")
+(len (string->path "abc"))
+(len (make-hash `((a . 1)(b . 2)(c . 3))))
+]
+
+Perhaps ironically, positive integers do not have a length.
+
+@examples[#:eval my-eval
+(len 3)]