From 410c4c96d5eda5b0b68f386e4ec2afd90543641f Mon Sep 17 00:00:00 2001
From: Vitor Santos Costa <vsc@dcc.fc.up.pt>
Date: Wed, 4 Aug 2010 23:26:50 +0100
Subject: [PATCH] Ulrich Neumerkel's lambda expressions.

---
 changes-6.0.html    |  3 +-
 docs/yap.tex        | 82 +++++++++++++++++++++++++++++++++++++++++++--
 library/Makefile.in |  1 +
 3 files changed, 83 insertions(+), 3 deletions(-)

diff --git a/changes-6.0.html b/changes-6.0.html
index 1af7b9640..a4c4712d7 100644
--- a/changes-6.0.html
+++ b/changes-6.0.html
@@ -16,7 +16,8 @@
 <h1>Changes in YAP-6</h1>
 
 <h2>Yap-6.0.7:</h2>
-<ul> FIXED: make install clpqr was broken if we used local install_sh .</li>
+<ul>
+<li> FIXED: make install in clpqr was broken if we used local install_sh .</li>
 <li> DELETE: atan/2 arithmetic function, use atan2/2 instead (WG17).</li>
 <li> FIXED: compilation in Solaris was broken because  of conflict in
   declaration of gethostname.</li>
diff --git a/docs/yap.tex b/docs/yap.tex
index 325e5c7c4..e17376ddb 100644
--- a/docs/yap.tex
+++ b/docs/yap.tex
@@ -198,6 +198,7 @@ Subnodes of Library
 * AVL Trees:: Predicates to add and lookup balanced binary  trees.
 * Heaps:: Labelled binary tree where the key of each node is less
     than or equal to the keys of its children.
+* Lambda:: Ulrich Neumerkel's Lambda Library
 * LineUtilities:: Line Manipulation Utilities
 * Lists:: List Manipulation
 * MapList:: SWI-Compatible Apply library.
@@ -8465,6 +8466,7 @@ Library, Extensions, Built-ins, Top
 * Heaps:: Labelled binary tree where the key of each node is less
     than or equal to the keys of its children.
 * LAM:: LAM MPI
+* Lambda:: Ulrich Neumerkel's Lambda Library
 * Lists:: List Manipulation
 * LineUtilities:: Line Manipulation Utilities
 * MapList:: SWI-Compatible Apply library.
@@ -12503,7 +12505,7 @@ The path @var{Path} is a path starting at vertex @var{Vertex} in graph
 
 @end table
 
-@node UnDGraphs, LAM , DGraphs, Library
+@node UnDGraphs, Lambda , DGraphs, Library
 @section Undirected Graphs
 @cindex undirected graphs
 
@@ -12599,7 +12601,83 @@ directed graph @var{DGraph}.
 
 @end table
 
-@node LAM, , UnDGraphs, Library
+@node Lambda, LAM, UnDGraphs, Library
+@section Lambda Expressions
+@cindex Lambda Expressions
+
+
+This library, designed and implemented by Ulrich Neumerkel, provides
+lambda expressions to simplify higher order programming based on @code{call/N}.
+
+Lambda expressions are represented by ordinary Prolog terms.  There are
+two kinds of lambda expressions:
+
+@example
+    Free+\X1^X2^ ..^XN^Goal
+
+         \X1^X2^ ..^XN^Goal
+@end example
+
+The second is a shorthand for@code{ t+\X1^X2^..^XN^Goal}, where @code{Xi} are the parameters.
+
+@var{Goal} is a goal or continuation (Syntax note: @var{Operators} within @var{Goal}
+require parentheses due to the low precedence of the @code{^} operator).
+
+Free contains variables that are valid outside the scope of the lambda
+expression. They are thus free variables within.
+
+All other variables of @var{Goal} are considered local variables. They must
+not appear outside the lambda expression. This restriction is
+currently not checked. Violations may lead to unexpected bindings.
+
+In the following example the parentheses around @code{X>3} are necessary.
+
+@example
+?- use_module(library(lambda)).
+?- use_module(library(apply)).
+
+?- maplist(\X^(X>3),[4,5,9]).
+true.
+@end example
+
+In the following @var{X} is a variable that is shared by both instances
+of the lambda expression. The second query illustrates the cooperation
+of continuations and lambdas. The lambda expression is in this case a
+continuation expecting a further argument.
+
+@example
+?- Xs = [A,B], maplist(X+\Y^dif(X,Y), Xs).
+Xs = [A, B],
+dif(X, A),
+dif(X, B).
+
+?- Xs = [A,B], maplist(X+\dif(X), Xs).
+Xs = [A, B],
+dif(X, A),
+dif(X, B).
+
+@end example
+
+The following queries are all equivalent. To see this, use
+the fact @code{f(x,y)}.
+
+@example
+?- call(f,A1,A2).
+?- call(\X^f(X),A1,A2).
+?- call(\X^Y^f(X,Y), A1,A2).
+?- call(\X^(X+\Y^f(X,Y)), A1,A2).
+?- call(call(f, A1),A2).
+?- call(f(A1),A2).
+?- f(A1,A2).
+A1 = x,
+A2 = y.
+@end example
+
+Further discussions
+at @url{http://www.complang.tuwien.ac.at/ulrich/Prolog-inedit/ISO-Hiord}.
+
+
+@node LAM, , Lambda, Library
 @section LAM
 @cindex lam
 
diff --git a/library/Makefile.in b/library/Makefile.in
index af5c2a2ad..ced0b98f9 100644
--- a/library/Makefile.in
+++ b/library/Makefile.in
@@ -44,6 +44,7 @@ PROGRAMS= \
 	$(srcdir)/gensym.yap \
 	$(srcdir)/hacks.yap \
 	$(srcdir)/heaps.yap \
+	$(srcdir)/lambda.pl \
 	$(srcdir)/lineutils.yap \
 	$(srcdir)/lists.yap \
 	$(srcdir)/nb.yap \