-Search for partial matches to STRING in ALIST.
-Each car of each element of ALIST is tested to see if it begins with STRING.
-The value is a list of all the strings from ALIST that match.
-ALIST can be an obarray instead of an alist.
-Then the print names of all symbols in the obarray are the possible matches.
-
-ALIST can also be a function to do the completion itself.
-It receives three arguments: the values STRING, PREDICATE and t.
-Whatever it returns becomes the value of `all-completions'.
-
-If optional third argument PREDICATE is non-nil,
-it is used to test each possible match.
-The match is a candidate only if PREDICATE returns non-nil.
-The argument given to PREDICATE is the alist element or
-the symbol from the obarray.
+Search for partial matches to STRING in COLLECTION.
+COLLECTION must be an alist, an obarray, or a function.
+Each string in COLLECTION is tested to see if it begins with STRING.
+The value is a list of all the strings from COLLECTION that match.
+
+If COLLECTION is an alist, the cars of the elements of the alist
+\(which must be strings) form the set of possible completions.
+
+If COLLECTION is an obarray, the names of all symbols in the obarray
+are the possible completions.
+
+If COLLECTION is a function, it is called with three arguments: the
+values STRING, PREDICATE and t. Whatever it returns becomes the
+value of `all-completions'.
+
+If optional third argument PREDICATE is non-nil, it is used to test
+each possible match. The match is a candidate only if PREDICATE
+returns non-nil. The argument given to PREDICATE is the alist element
+or the symbol from the obarray.