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list-bindings

This module provides 6 binding constructs, including a version of Common Lisp's destructuring-bind but with shorter name, and - as an application - define-macro. Contrary to the bindings egg, destructuring is only done for list expressions, which is sufficient for low-level macros.

Programming interface

list-bindings

[procedure] (list-bindings [sym])

documentation procedure. Without sym produces a list of exported symbols and with sym that sym's documentation

bind

[syntax] (bind pat seq xpr . xprs)

binds pattern variables of pat, a nested lambda-list, to subexpressions of the list expression seq and executes xpr . xprs in this context

bind-let*

[syntax] (bind-let* ((pat seq) ...) xpr . xprs)

binds pattern variables of pat to corresponding subexpressions of seq ... in sequence and executes body xpr . xprs in this context.

bind-let

[syntax] (bind-let ((pat seq) ...) xpr . xprs)

binds pattern variables of pat to corresponding subexpressions of seq ... in parallel and executes body xpr . xprs in this context.

bindable?

[syntax] (bindable? pat . pats)

returns a predicate which checks, if its only list argument matches any of the patterns pat . pats.

bind-case

[syntax] (bind-case seq clause . clauses)

where seq is a list expression and each clause is of the form (pat xpr . xprs), with pat a nested lambda-list.

Matches seq against each pattern pat in sequence and executes the corresponding body xpr . xprs of the first match.

bind/cc

[syntax] (bind/cc cont xpr . xprs)

syntactic sugar for call-with-current-continuation. Captures the current contiunuation, binds it to cont and evaluates the body xpr . xprs in this context.

define-macro

[syntax] (define-macro (name . args) (renaming (prefix . prefixed-identifiers) (comparing keyword-predicate body)))
[syntax] (define-macro (name . args) (renaming (prefix . prefixed-identifiers) body))
[syntax] (define-macro (name . args) (injecting identifiers (comparing keyword-predicates body)))
[syntax] (define-macro (name . args) (injecting identifiers body))
[syntax] (define-macro (name . args) (comparing keyword-predicate body))
[syntax] (define-macro (name . args) body)

where renaming and injecting and comparing are keywords, prefixed-identifiers is a list, where all identifiers share the same prefix, identifiers is a list, keyword-predicates is either null or of the form (suffix . suffixed-keywords), suffixed-keywords is a list, where all identifiers share the same suffix.

Simplifies implicit-renaming macros by destructuring the macro-code automatically. The defined macro is either implicit- or explicit-renaming depending on the chosen keyword injecting or renaming. The macro either provides identifiers bound to itself injected or prefixed-identifiers bound to itself with the prefixed stripped and renamed. Moreover the macro provides keyword-predicates, suffixed-keywords, to check if a symbol compares to the keyword-predicate's name with its suffix stripped. The short-hand versions simply add the missing clauses with empty lists, where a missing injecting or renaming clause is interpreted as injecting.

Requirements

None

Examples

 

(use list-bindings)

(bind a 1 a) ; -> 1
(bind (a b) '(1 2)  (list a b)) ; -> '(1 2)
(bind (x y z w) '(1 2 3 4) (list x y z w)) ; -> '(1 2 3 4)
(bind (x (y (z . u) . v) . w)
	'(1 (2 (3 4) 5) 6)
	(list x y z u v w)) ; -> '(1 2 3 (4) (5) (6))
(bind-let* (((a b) '(1 2)) ((x . y) '(3))) (list a b x y))
  ; -> '(1 2 3 ())
(bind-let* (((a b) '(1 2)) ((x . y) (list a))) (list a b x y))
  ; -> '(1 2 1 ())
(bind-let (((a b) '(1 2)) ((x . y) '(3 4 4))) (list a b x y))
  ; -> '(1 2 3 (4 4))
(bind-case '(1 (2 3))
	((x (y z)) (list x y z))
	((x (y . z)) (list x y z))
	((x y) (list x y))) ; -> '(1 2 3)
(bind-case '(1 (2 3))
	((x (y . z)) (list x y z))
	((x y) (list x y))
	((x (y z)) (list x y z))) ; -> '(1 2 (3)))
(bind-case '(1 (2 3))
	((x y) (list x y))
	((x (y . z)) (list x y z))
	((x (y z)) (list x y z))) ; -> '(1 (2 3))
(bind-case '(1 (2 . 3))
	((x y) (list x y))
	((x (y . z)) (list x y z))
	((x (y z)) (list x y z))) ; -> '(1 (2 . 3))
(letrec (
	(my-map
		(lambda (fn lst)
			(bind-case lst
				(() '())
				((x . xs) (cons (fn x) (map fn xs))))))
	)
	(my-map add1 '(1 2 3))) ; -> '(2 3 4)
((bindable? (a b)) '(1 2)) ; -> #t 
((bindable? (a . b)) '(1)) ; -> #t
((bindable? (x)) '(name 1)) ;-> #f
((bindable? (_ x)) '(name 1)) ; -> #t
((bindable? (_ x)) '(name 1 2)) ;-> #f
((bindable? (_) (_ x y)  (_ x y)) '(name 1 2)) ; -> #t

(define-er-macro (efreeze xpr)
	(renaming (% %lambda)
		(comparing ()
			`(,%lambda () ,xpr))))
((efreeze 3)) ; -> 3
(define-macro (ifreeze xpr)
	`(lambda () ,xpr))
((ifreeze 5)) ; -> 5
(define-macro (alambda args xpr . xprs)
	(injecting (self)
		`(letrec ((,self (lambda ,args ,xpr ,@xprs)))
			 ,self)))
(define ! (alambda (n) (if (zero? n) 1 (* n (self (- n 1))))))
(! 5) ; -> 120
(define-macro (foo pair)
	(comparing (? bar?) `(if ,(bar? (car pair)) ,@(cdr pair) 'unchecked)))
(foo (bar 'checked)) ; -> 'checked
(foo (baz 'checked)) ; -> 'unchecked)
(define-macro (baz pair)
	(renaming (% %if)
		(comparing (? bar?)
			`(,%if ,(bar? (car pair)) ,@(cdr pair) 'unchecked))))
(baz (bar 'checked)) ; -> 'checked
(baz (foo 'checked)) ; -> 'unchecked
(define-macro (swap! x y)
  `(let ((tmp ,x)) (set! ,x ,y) (set! ,y tmp)))
(let ((x 'x) (y 'y)) (swap! x y) (list x y))
  ; -> '(y x)

Last update

Aug 08, 2013

Author

Juergen Lorenz

License

 
Copyright (c) 2011-2013, Juergen Lorenz
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Version History
1.3
define-macro now incorporates define-ir-macro and define-er-macro, which are no longer exported
1.2
define-macro added
1.1
bind-let and bind-let* added
1.0
initial import