miscmacros
Note: This is taken from the Chicken Wiki, where a more recent version could be available.
Various useful little macros.
None
<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>(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 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)</macro>
Equivalent to (set! LOC (add1 LOC)).
<macro>(dec! LOC)</macro>
Equivalent to (set! LOC (sub1 LOC)).
<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 IDs). 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 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<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.
Copyright (c) 2004-2005, Felix L. Winkelmann
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