Add util-proc with basic arity predicates.

src/Makefile

@@ -46,7 +46,7 @@ HACKERBASE-OBJS=hackerbase.o testing.o listing.o month.o period.o ansi.o	\
 	 bank-account.o bank-fio.o members-payments.o member-parser.o	\
 	 web-static.o environment.o mailman.o util-set-list.o		\
 	 util-time.o util-tag.o util-io.o util-string.o util-io.o	\
-	 util-list.o util-parser.o texts.o tests.o
+	 util-list.o util-parser.o texts.o tests.o util-proc.o
 
 .PHONY: imports
 imports: $(HACKERBASE-DEPS)
@@ -69,7 +69,7 @@ install: static
 	$(CSC) -c -static $<
 
 %.import.scm: %.scm
-	rm -f $@
+	@rm -f $@
 	$(CSC) -P -J $<
 
 ################################################################
@@ -303,3 +303,8 @@ TESTS-SOURCES=tests.scm listing.import.scm util-dict-list.import.scm	\
 
 tests.o: tests.import.scm
 tests.import.scm: $(TESTS-SOURCES)
+
+UTIL-PROC-SOURCES=util-proc.scm
+
+util-proc.o: util-proc.import.scm
+util-proc.import.scm: $(UTIL-PROC-SOURCES)

src/util-proc.scm

@@ -0,0 +1,75 @@
+;;
+;; util-proc.scm
+;;
+;; Auxiliary procedure functions.
+;;
+;; ISC License
+;;
+;; Copyright 2023 Brmlab, z.s.
+;; Dominik Pantůček <dominik.pantucek@trustica.cz>
+;;
+;; Permission to use, copy, modify, and/or distribute this software
+;; for any purpose with or without fee is hereby granted, provided
+;; that the above copyright notice and this permission notice appear
+;; in all copies.
+;; 
+;; THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
+;; WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
+;; WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
+;; AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR
+;; CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
+;; OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
+;; NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+;; CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+;;
+
+(declare (unit util-proc))
+
+(module
+ util-proc
+ (
+  procedure-arity=?
+  procedure-arity>=?
+  procedure-arity>?
+  )
+
+ (import scheme
+	 (chicken base))
+ 
+ ;; Returns two values: the proper part of the list length and #t if
+ ;; there is an improper list end
+ (define (improper-list-info lst)
+   (let loop ((lst lst)
+	      (len 0))
+     (if (symbol? lst)
+	 (values len #t)
+	 (if (null? lst)
+	     (values len #f)
+	     (loop (cdr lst)
+		   (add1 len))))))
+
+ ;; Returns two values: the number of mandatory arguments and
+ ;; information whether the procedure accepts optional arguments
+ (define (procedure-arity-info proc)
+   (let-values (((len rest?) (improper-list-info (procedure-information proc))))
+     (values (sub1 len) rest?)))
+
+ ;; Returns true if given procedure arity is exactly n
+ (define ((procedure-arity=? n) proc)
+   (let-values (((args rest?) (procedure-arity-info proc)))
+     (and (not rest?)
+	  (= args n))))
+
+ ;; Returns true if given procedure arity is greater than or equal to n
+ (define ((procedure-arity>=? n) proc)
+   (let-values (((args rest?) (procedure-arity-info proc)))
+     (or rest?
+	 (>= args n))))
+
+ ;; Returns true if given procedure arity is greater than n
+ (define ((procedure-arity>? n) proc)
+   (let-values (((args rest?) (procedure-arity-info proc)))
+     (or rest?
+	 (> args n))))
+
+ )