;;;; string-utils.scm  -*- Hen -*-
;;;; Kon Lovett, Aug '10

(module string-utils

  (;export
    make-string*)

  (import
    scheme
    chicken
    (only data-structures
      alist-ref alist-update!)
    lookup-table
    miscmacros
    (only type-checks
      check-integer check-char))

  (require-library
    data-structures
    miscmacros lookup-table type-checks)

  (declare
    (bound-to-procedure
      ##sys#make-string))

;; Memeoized `make-string'

(define make-string*
  (let ((+strings+ (make-dict eqv?)))
    (lambda (len #!optional (ch #\space))
      (if* (dict-ref +strings+ ch)
        (or (dict-ref it len)
            (let ((str (##sys#make-string len ch)))
              (dict-set! it len str)
              ; dict `it' already member of +strings+
              str ) )
        (begin
          (dict-update-dict! +strings+ ch)
          (make-string* len ch) ) ) ) ) )

) ;module string-utils