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Various useful little macros.
Documentation[syntax] (let/cc K BODY ...)
Executes BODY ... with K bound to the current-continuation.[syntax] (until TEST BODY ...)
Executes BODY ... repeatedly while the expression TEST returns #f.[syntax] (repeat TIMES BODY ...)
Executes BODY ... TIMES times.[syntax] (repeat* TIMES BODY ...)
Executes BODY ... TIMES times, with the variable it bound to the count-down value.[syntax] (dotimes (VAR TIMES [FINAL]) BODY ...)
Executes BODY ... TIMES times, with the variable VAR bound to the count-up value.
Returns the result of the FINAL expression or (void) when no FINAL expression.[syntax] (while TEST BODY ...)
Executes BODY ... repeatedly until the expression TEST returns #f.[syntax] (while* TEST BODY ...)
Executes BODY ... repeatedly, with the result of TEST bound to the variable it, until the expression TEST returns #f.[syntax] (if* X Y [Z])
The anaphoric if: if the expression X evaluates to a true value, the expression Y will be executed with the result of X bound to the variable it. If X is false, then Z (if supplied) will be evaluated:
(if* (> 3 1) it) ==> #t (if* (memq 'a '(b a c)) (cdr it) 99) ==> (c) (if* #f it 1) ==> 1 (if* #f #f) ==> #<unspecified>[syntax] (push! X LOC)
(set! LOC (cons X LOC))
Note that LOC may be any settable location.[syntax] (pop! LOC)
Returns the first element from the list stored in the location LOC and sets LOC to the cdr of the previous value.[syntax] (inc! LOC [AMOUNT])
Equivalent to (set! LOC (+ LOC AMOUNT)). AMOUNT defaults to 1. Returns the new value.[syntax] (dec! LOC [AMOUNT])
Equivalent to (set! LOC (- LOC AMOUNT)). AMOUNT defaults to 1. Returns the new value.[syntax] (ignore-errors BODY ...)
Evaluates the expressions in BODY .... If any exceptions should be raised during execution of the body, then the exceptions will be caught, and ignore-errors returns #f.[syntax] (begin0 BODY ...)
Evaluates BODY ... just like begin, but instead of returning the last value(s), begin0 returns the result (or the results) of the first expression in BODY ....[syntax] (define-enum ->INT ->SYM ID ...)
Defines an enumeration. The variables ID, ... are bound to the exact integers 0, 1, ... with define-constant. ID may also take the form (ID N), in which case the counter will be set to the exact integer N for that variable, and continue upward normally from there. A procedure named ->INT will be defined that takes a symbols and returns the respective integer. A procedure ->SYM will also be defined that takes an integer and returns the respective symbol (from the set of IDs). If a symbol doesn't map to an integer (or vice versa), #f is returned.[syntax] (define-optionals ((VAR1 DEFAULT1) ...) ARGUMENTS)
Defines the globals VAR1 ... with the values taken from the list ARGUMENTS, or with DEFAULT1 ..., if the list is shorter.[syntax] (define-parameter VAR [VALUE [GUARD]])
(define VAR (make-parameter VALUE [GUARD]))
VALUE defaults to (void).[syntax] (ignore-values EXP)
Evaluates EXP ignoring any return values. Returns an unspecified value.[syntax] (modify-location LOC PROC)
Expands into a call to PROC with two arguments: a zero-argument procedure for retrieving the value from the settable location LOC and a one argument procedure for setting the value of LOC. Care is taken to evaluate any subforms in LOC only once.
modify-location is intended to create modification macros for generalized locations (as in SRFI-17.
(define-syntax-rule (increment! loc) (modify-location loc (lambda (ref upd) (upd (add1 (ref)))) ) ) (define x (vector 123)) (increment! (vector-ref x (print 0))) ; sets x to #(124) and prints "0" only once[syntax] (modify! LOC PROC)
Modifies the contents of location LOC by applying the procedure PROC to it's contents and setting LOCs to the result. LOC may be any settable location.
(define-macro (increment! loc) `(modify! ,loc add1) )[syntax] (exchange! LOC1 LOC2)
Exchanges the contents of the given locations. LOC1 and LOC2 may be any settable locations.[syntax] (define-syntax-rule (NAME ARGUMENT ...) TEMPLATE)
(define-syntax NAME (syntax-rules () ((_ ARGUMENT ...) TEMPLATE)))[syntax] (doto X FORM ...)
Inserts the value of X into the procedure-call forms FORM ... as the first argument and returns that value:
(doto (some-data) (init-data) (show-data window) (throw-away-data)) => (let ((tmp (some-data))) (init-data tmp) (show-data tmp window) (throw-away-data tmp) tmp)[syntax] (ecase EXP ((LITERAL ...) BODY ...) ...)
Similar to case, but signals an error if no clause matches.
- 2.91 Added doto (contributed by Martin DeMello)
- 2.9 inc! and dec! return the new value
- 2.8 added define-syntax-rule
- 2.7 added import-only extension property and allowed optional increment/decrement for inc! and dec!
- 2.6 removed -host option from setup script
- 2.5 Add counter set capability to define-enum [zbigniew]
- 2.4 Added modify! and exchange! [felix]
- 2.3 Added dotimes [by Kon Lovett]
- 2.2 Fixed bug in pop!
- 2.1 Added modify-location and made location-modification macros general for set!table locations
- 2.0 Added some simple looping constructs [by Kon Lovett]
- 1.9 Added while* [by Kon Lovett]
- 1.8 Fixed bug in if* [Thanks to Houman Zolfaghari]
- 1.7 Added ignore-values and define-parameter
- 1.6 Fixed bug in if* [Thanks to Michele Simionato]
- 1.5 removed shift! and rotate!
- 1.4 ignore-errors returns #f on exception
- 1.3 Added missing documentation for define-optionals
- 1.2 Added define-enum [by Alex Shinn]
- 1.1 Added inc! and dec!
- 1.0 Initial release
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