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Article contents:[[tags: egg]] == miscmacros [[toc:]] === Description Various useful little macros. Note: since version 2.95, this extension does not support {{doto}} anymore. It is provided instead by Moritz Heidkamp's [[clojurian]] egg, among other other interesting Clojure macros. === Author [[/users/felix winkelmann|felix winkelmann]] === Repository This egg is hosted on the CHICKEN Subversion repository: [[https://anonymous@code.call-cc.org/svn/chicken-eggs/release/6/miscmacros|https://anonymous@code.call-cc.org/svn/chicken-eggs/release/6/miscmacros]] If you want to check out the source code repository of this egg and you are not familiar with Subversion, see [[/egg-svn-checkout|this page]]. === Requirements None === Documentation <macro>(let/cc K BODY ...)</macro> Executes {{BODY ...}} with {{K}} bound to the current-continuation. <macro>(until TEST BODY ...)</macro> Executes {{BODY ...}} repeatedly while the expression {{TEST}} returns {{#f}}. <macro>(repeat TIMES BODY ...)</macro> Executes {{BODY ...}} {{TIMES}} times. <macro>(repeat* TIMES BODY ...)</macro> Executes {{BODY ...}} {{TIMES}} times, with the variable {{it}} bound to the count-down value. <macro>(dotimes (VAR TIMES [FINAL]) BODY ...)</macro> 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. <macro>(while TEST BODY ...)</macro> Executes {{BODY ...}} repeatedly until the expression {{TEST}} returns {{#f}}. <macro>(while* TEST BODY ...)</macro> Executes {{BODY ...}} repeatedly, with the result of {{TEST}} bound to the variable {{it}}, until the expression {{TEST}} returns {{#f}}. <macro>(select EXP ((KEY ...) EXP1 ...) ... [(else EXPn ...)])</macro> This is similar to {{case}}, but the keys are evaluated. <macro>(if* X Y [Z])</macro> 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> <macro>(push! X LOC)</macro> equivalent to (set! LOC (cons X LOC)) Note that {{LOC}} may be any settable location. <macro>(pop! LOC)</macro> Returns the first element from the list stored in the location {{LOC}} and sets {{LOC}} to the cdr of the previous value. <macro>(inc! LOC [AMOUNT])</macro> Equivalent to {{(set! LOC (+ LOC AMOUNT))}}. {{AMOUNT}} defaults to 1. Returns the new value. <macro>(dec! LOC [AMOUNT])</macro> Equivalent to {{(set! LOC (- LOC AMOUNT))}}. {{AMOUNT}} defaults to 1. Returns the new value. <macro>(ignore-errors BODY ...)</macro> 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}}. <macro>(begin0 BODY ...)</macro> 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 ...}}. <macro>(define-enum ->INT ->SYM ID ...)</macro> 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 {{ID}}s). If a symbol doesn't map to an integer (or vice versa), {{#f}} is returned. <macro>(define-optionals ((VAR1 DEFAULT1) ...) ARGUMENTS)</macro> Defines the globals {{VAR1 ...}} with the values taken from the list {{ARGUMENTS}}, or with {{DEFAULT1 ...}}, if the list is shorter. <macro>(define-parameter VAR [VALUE [GUARD]])</macro> Equivalent to (define VAR (make-parameter VALUE [GUARD])) {{VALUE}} defaults to {{(void)}}. <macro>(ignore-values EXP)</macro> Evaluates {{EXP}} ignoring any return values. Returns an unspecified value. <macro>(modify-location LOC PROC)</macro> 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 [[http://srfi.schemers.org/srfi-17|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 <macro>(modify! LOC PROC)</macro> 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) ) <macro>(exchange! LOC1 LOC2)</macro> Exchanges the contents of the given locations. LOC1 and LOC2 may be any settable locations. <macro>(define-syntax-rule (NAME ARGUMENT ...) TEMPLATE)</macro> Shorthand for (define-syntax NAME (syntax-rules () ((_ ARGUMENT ...) TEMPLATE))) <macro>(ecase EXP ((LITERAL ...) BODY ...) ...)</macro> Similar to {{case}}, but signals an error if no clause matches. <macro>(ensure PREDICATE EXP [ARGUMENTS ...])</macro> Evaluates the expression {{EXP}} and applies the one-argument procedure {{PREDICATE}} to the result. If the predicate returns {{#f}} an error is signaled, otherwise the result of {{EXP}} is returned. If compiled in ''unsafe'' mode (either by specifying the {{-unsafe}} compiler option or by declaring {{(unsafe)}}), then this expression expands to an unspecified value. If specified, the optional {{ARGUMENTS}} are used as arguments to the invocation of the error-signalling code, as in {{(error ARGUMENTS ...)}}. If no {{ARGUMENTS}} are given, a generic error message is displayed with the offending value and {{PREDICATE}} expression. <macro>(eval-when (SITUATION ...) EXP ...)</macro> Controls evaluation/compilation of subforms. {{SITUATION}} should be one of the symbols {{eval}}, {{compile}} or {{load}}. When encountered in the evaluator, and the situation specifier {{eval}} is not given, then this form is not evaluated and an unspecified value is returned. When encountered while compiling code, and the situation specifier {{compile}} is given, then this form is evaluated at compile-time. When encountered while compiling code, and the situation specifier {{load}} is not given, then this form is ignored and an expression resulting into an unspecified value is compiled instead. The following table should make this clearer: <table> <tr><th></th><th>In compiled code</th><th>In interpreted code</th></tr> <tr><td>{{eval}}</td><td>ignore</td><td>evaluate</td></tr> <tr><td>{{compile}}</td><td>evaluate at compile time</td><td>ignore</td></tr> <tr><td>{{load}}</td><td>compile as normal</td><td>ignore</td></tr> </table> === Changelog * 1.1 Port to CHICKEN 6 * 1.0 Initial release for CHICKEN 5, based on version 2.95 of CHICKEN 4, added {{ensure}}, {{select}} and {{eval-when}} === License Copyright (c) 2006-2018, The CHICKEN Team 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. Description of your changes:

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