alist.scm

#|
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|#

;; manipulate association lists

(define (alist-ref alist key . def0)
  (let ((def (if (fx= (length def0) 1) (car def0) #f)))
    (if (not (list? alist)) def
      (let* ((a (assoc key alist)))
        (if (list? a) (if (= (length a) 1) def (cadr a)) 
          (if (pair? a) (cdr a) def))))))

(define (alist-refstr alist key defstr)
  (let ((res (alist-ref alist key defstr)))
    (if (string? res) res
      (if (number? res) (number->string res) 
        (if (symbol? res) (symbol->string res) defstr)))))

(define (alist-refnum alist key defnum)
  (let* ((res (alist-ref alist key defnum)))
    (if (number? res) res
      (if (string? res) 
         (let ((tmp (string->number res)))
           (if (number? tmp) tmp defnum))
        (if (symbol? res)
          (let ((tmp (string->number (symbol->string res))))
            (if (number? tmp) tmp defnum)) defnum)))))

(define (alist-delkeys alist . keys)
  (define (list-del-item lst item)
    (if (not item) lst (cond
      ((fx= (length lst) 0) lst)
      ((equal? item (car lst)) (cdr lst))
      (else (cons (car lst) (list-del-item (cdr lst) item)))
    )))
  (let loop ((ks keys)(res alist))
    (if (= (length ks) 0) res
      (let ((item (assoc (car ks) res)))
        (loop (cdr keys) (list-del-item res item))))))
   
(define (alist-set alist . keyvals)
  (let loop ((kvs keyvals)(res (if alist alist '())))
    (if (< (length kvs) 2) 
      (append (alist-delkeys res 'timestamp) (list (list 'timestamp (time->seconds (current-time)))))
      (loop (cddr kvs) (append (alist-delkeys res (car kvs)) (list (list (car kvs) (cadr kvs))))))))

(define (alist-set-notime alist . keyvals)
  (let loop ((kvs keyvals)(res (if alist alist '())))
    (if (< (length kvs) 2) 
      res
      (loop (cddr kvs) (append (alist-delkeys res (car kvs)) (list (list (car kvs) (cadr kvs))))))))


(define (write-alist-to-file filename alist)
  (with-output-to-file filename
    (lambda ()
      (write alist))))

(define (read-alist-from-file filename)
  (with-input-from-file filename
    (lambda ()
      (read))))

;; eof