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list-bindings

This module provides 4 binding constructs, including a version of Common Lisp's destructuring-bind but with shorter name, as well as two macros to simplyfy the definition of low-level macros. 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-ir-macro

[syntax] (define-ir-macro (name . args) (injecting identifiers (comparing keyword-predicates xpr . xprs)))

where injecting and comparing are keywords and keyword-predicates is either null or of the form (suffix . suffixed-keywords). Simplifies implicit-renaming macros by destructuring the macro-form (name . args), injecting the identifiers and providing keyword-predicates, suffixed-keywords, to check if a symbol compares to the keyword-predicate's name with its suffix stripped. Note, that this syntax shows nicely in the header, if there are injected identifiers, i.e. if the macro is hygienic or not, and what the additional keywords are, namely the suffixed-keywords with suffix stripped.

define-er-macro

[syntax] (define-er-macro (name . args) (renaming (prefix . prefixed-identifiers) (comparing keyword-predicate xpr . xprs)))

where renaming and comparing are keywords and keyword-predicates is either null or of the form (suffix . suffixed-keywords). Simplifies explicit-renaming macros by destructuring the macro-form (name . args), binding prefixed-identifiers to its own name but with prefix stripped and providing keyword-predicates, suffixed-keywords, to check if a symbol compares to the keyword-predicate's name with the suffix stripped. Note, that contrary to the identifiers list in define-ir-macro, the list prefixed-identifiers exposes information of the macro's implementation; this list is usually updated in the process of macro-writing. The list suffixed-keywords, on the other hand, provides information on the additional keywords of the macro, if any: Simply strip the suffix.

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

Last update

Aug 05, 2013

Author

Juergen Lorenz

License

 
Copyright (c) 2011-2013, Juergen Lorenz
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Version History
1.1
bind-let and bind-let* added
1.0
initial import