You are looking at historical revision 9467 of this page. It may differ significantly from its current revision.
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) BODY ...)
Executes BODY ... TIMES times, with the variable VAR bound to the count-up value.[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 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)
Equivalent to (set! LOC (add1 LOC)).[syntax] (dec! LOC)
Equivalent to (set! LOC (sub1 LOC)).[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-macro (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.
- 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
Copyright (c) 2004-2005, Felix L. Winkelmann All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. Neither the name of the author nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.