From Newsgroup: comp.lang.lisp

Barry Margolin wrote:

(defun map-with-constant (mapping-function function constant &rest lists)
(apply mapping-function function (circular-list constant) lists))

This can then be used as
(map-with-constant #'mapcar #'cons 1 '(1 2 3)) =>
((1 . 1) (1 . 2) (1 . 3)).

Scheme

(% map (cons 'X _) '(1 2 3))
===>
((X . 1) (X . 2) (X . 3))

Given:


;; Anaphoric macro to abbreviate lambdas for higher-order functions.
;; Uses "_" for 1 argument;
;; uses "A:" and "B:" and so on for 2 or more arguments.
;; This version works under both Gauche Scheme
;; and Racket. Racket needs:
;; (require compatibility/defmacro)
;; When used with functions such as "map" and "fold", the macro
;; can deduce the number of arguments the lambda will receive.
;; The number of arguments can be specified by an integer
;; after the function name. For example:
;; (% 2 lset-adjoin (eq? B: (char-upcase A:)) '(#\M #\N) #\m #\o)
;;
(define-macro %
(case-lambda
((func expr List) `(,func (lambda(_) ,expr) ,List))
((func expr . more)
;; Number of arguments received by the lambda.
(let ((n (if (integer? func)
(begin0
func
(set! func expr)
(set! expr (car more))
(set! more (cdr more)))
(length more))))
(let* ((nums (do ((i n (- i 1))
(r '() (cons (+ i 64) r))) ((= 0 i) r)))
(vnames
(map (lambda(n)
(string->symbol (string (integer->char n) #\:)))
nums)))
`(,func (lambda ,vnames ,expr) ,@more))))))
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