Procedure utilities documentation.

doc/utils.md

@@ -207,6 +207,52 @@ pair consisting of symbol created by interning the string of
 non-whitespace characters before the first whitespace character and
 the string with the rest of the line.
 
+### Proc
+
+    (import util-proc)
+
+This module provides a few simple procedures for querying properties
+of other procedures.
+
+    ((procedure-arity=? n) proc)
+
+* ```n``` - integer representing the number of arguments
+* ```proc``` - procedure to query
+
+Returns true if the procedure ```proc``` accepts exactly ```n```
+arguments.
+
+    ((procedure-arity>=? n) proc)
+
+* ```n``` - integer representing the number of arguments
+* ```proc``` - procedure to query
+
+Returns true if the procedure ```proc``` accepts at least ```n```
+arguments.
+
+    ((procedure-arity>? n) proc)
+
+* ```n``` - integer representing the number of arguments
+* ```proc``` - procedure to query
+
+Returns true if the procedure ```proc``` accepts more than ```n```
+arguments.
+
+    (procedure-num-args proc)
+
+* ```proc``` - procedure to check
+
+Returns the number of mandatory arguments.
+
+    (procedure-arg-names proc)
+
+* ```proc``` - procedure to check
+
+Returns the (possibly improper) list of arguments the procedure
+```proc``` accepts. If it accepts arbitrary number of arguments, it is
+signalled by simple symbol instead of pair at the last position. If it
+accepts an exact number of arguments, it returns a proper list.
+
 ### Set (List)
 
     (import util-set-list)