prelude.ss

;; Our by-now usual prelude.

(define (compiler-error . bobbins)
  (error bobbins))

(define (runtime-error . bobbins)
  (error bobbins))

;; A unique value for uninitialised variables.
(define undefined-value '(constant . undefined))

(define (init* self . fields)
  (define (init1 fields)
    (if (pair? fields)
        (if (pair? (cdr fields))
            (begin
              ((car fields) self (cadr fields))
              (init1 (cddr fields)))
            (error "Field spec not in format (:mutator! value ...)" fields))))
  (init1 fields))

(define-macro (-> value . rest)
  (cond
   ((null? rest)
    value)
   ((pair? rest)
    (let ((next (car rest)))
      (if (pair? next)
          `(-> (,(car next) ,value ,@(cdr next)) ,@(cdr rest))
          `(-> (,next ,value) ,@(cdr rest)))))))

;; A working implementation of compose, since it seems to be missing from SISC
(define (compose . procs)
  (if (null? procs)
      (lambda (v) v)
      (lambda (v) ((car procs) ((apply compose (cdr procs)) v)))))