#file. LISTUT.HLP

#updated. 1 October 1984

#purpose.
Provides list processing utilities

#datatype.
Operates on standard Prolog lists, of form
		[Head|Tail]
or
		[Item, Item, Item .....]

#needs.
This module requires
	select/3	(from SetUtl.Pl) for perm/2
	listtoset/2	(from SetUtl.Pl) for remove_dups/2
If you don't want those routines, it can be used on its own.

#author.
I am not sure how much of the original code was by Bob Welham
and how much by Lawrence Byrd.  The layout and comments are by
R.A.O'Keefe, as are nth*, same_length, shorter_list, and subseq*.
Keys_and_values has moved to PROJEC.PL.

#commands.
append(Prefix, Suffix, Combined)	Append list Sufffix to list Prefix
					giving Combined.
correspond(X, Xlist, Y,Ylist)		Is X in same position in Xlist as
					as Y is in Ylist?
delete(List, Elem, Residue)		Delete Elem from List leaving Residue
last(Last, List)			Is Last the last element in List?
nextto(X, Y, List)			Do X and Y appear side-by-side in List?
nth0(N, List, Elem)			Unify Elem with N'th element of List
					Head of list is element number 0
nth0(N, List, Elem, Rest)		Unify Elem with N'th element of List
					and Rest with the other elements.
					Head of list is element number 0
nth1(N, List, Elem)			As nth0. Head of list is element number
					1
nth1(N, List, Elem, Rest)		As nth0. Head of list is element number
					1
nmember(Elem, List, Index)		Is Elem the Index'th member of List?
numlist(Lower, Upper, List)		Does list consist of integers
					[Lower, ..., Upper] ?
perm(List, Perm)			Generates permutations of List
perm2(A, B, C, D)			Is {A,B} = {C, D} ?
remove_dups(List, Pruned)		Pruned is List with no duplicate
					elements.
rev(List, Reversed)			As reverse.
reverse(List, Reversed)			Reversed is reverse of List
same_length(List1, List2)		Is List1 the same length as List2?
select(X, Xlist, Y, Ylist)		Xlist and Ylist are identical apart
					from K'th elements (X and Y).
shorter-list(Short, Long)		Is list Short shorter than list Long?
subseq(Seq, Subseq, Complement)		If Subseq is a subsequence of Seq then
					Complement is the other elements of Seq
subseq0(Sequence, Subsequence)		Is Subsequence a sub-sequence of or
					the same sequence as Sequence?
subseq1(Sequence, Subsequence)		Is Subsequence a subsequence of
					Sequence?
sumlist(Numbers, Total)			Total is sum of integers in list
					Numbers

#user_keys.
list, listut, sequence, sequences.