utils: Add drop-first-last.

scribblings/utils.scrbl

@@ -222,6 +222,16 @@ Reads a list of symbols from a string.
 (read-symbol-list "a b c")
 ]}
 
+@defproc[(drop-first-last (str String)) String]{
+
+Removes the first and the last symbol of a given string.
+
+Useful for removing the parentheses in string representations of lists.
+
+@examples[#:eval utils-evaluator
+(drop-first-last "(a b)")
+]}
+
 @section{Additional graph utilities}
 
 @section{Pretty printing}

utils-untyped.rkt

@@ -10,8 +10,7 @@
 
 (provide
  ;; Functions
- (contract-out [drop-first-last (-> string? string?)]
-               [list-sets->list-strings (-> (listof (set/c any/c)) (listof string?))]
+ (contract-out [list-sets->list-strings (-> (listof (set/c any/c)) (listof string?))]
                [pretty-print-set-sets (-> (set/c (set/c symbol?) #:kind 'dont-care) string?)]
                [update-vertices/unweighted (-> graph? (-> any/c any/c) graph?)]
                [update-graph (->* (graph?)

utils.rkt

@@ -9,7 +9,7 @@
          extract-symbols
          any->string stringify-variable-mapping string->any map-sexp
          read-org-sexp unorg unstringify-pairs
-         read-org-variable-mapping unorgv read-symbol-list
+         read-org-variable-mapping unorgv read-symbol-list drop-first-last
          ;; Syntax
          auto-hash-ref/explicit auto-hash-ref/:)
 
@@ -262,3 +262,11 @@
 (module+ test
   (test-case "read-symbol-list"
     (check-equal? (read-symbol-list "a b c") '(a b c))))
+
+(: drop-first-last (-> String String))
+(define (drop-first-last str)
+  (substring str 1 (- (string-length str) 1)))
+
+(module+ test
+  (test-case "drop-first-last"
+    (check-equal? (drop-first-last "(a b)") "a b")))