lambda calculus and free variables

git-svn-id: https://slps.svn.sourceforge.net/svnroot/slps@706 ab42f6e0-554d-0410-b580-99e487e6eeb2
grammarware · Nov 13, 2009 · c48555b · c48555b
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diff --git a/topics/exercises/lambda1/Makefile b/topics/exercises/lambda1/Makefile
@@ -0,0 +1,6 @@
+test:
+	swipl -f syntax.pro -t "write(term(`cat input.txt`)),nl"
+
+prompt:
+	swipl -s syntax.pro
+
diff --git a/topics/exercises/lambda1/input.txt b/topics/exercises/lambda1/input.txt
@@ -0,0 +1 @@
+lambda(f,lambda(g,lambda(x,apply(f,apply(g,x)))))
diff --git a/topics/exercises/lambda1/syntax.pro b/topics/exercises/lambda1/syntax.pro
@@ -0,0 +1,12 @@
+% see slides #147
+
+term(x).
+term(y).
+term(z).
+term(f).
+term(g).
+term(h).
+
+term(apply(M,N)) :- term(M), term(N).
+term(lambda(X,M)) :- term(X), term(M).
+
diff --git a/topics/exercises/lambda2/Makefile b/topics/exercises/lambda2/Makefile
@@ -0,0 +1,6 @@
+test:
+	swipl -f variables.pro -t "free(`cat input.txt`,FV),write(FV),nl"
+
+prompt:
+	swipl -s variables.pro
+
diff --git a/topics/exercises/lambda2/input.txt b/topics/exercises/lambda2/input.txt
@@ -0,0 +1 @@
+apply(lambda(x,y),lambda(z,z))
diff --git a/topics/exercises/lambda2/syntax.pro b/topics/exercises/lambda2/syntax.pro
@@ -0,0 +1,12 @@
+% see slides #147
+
+term(x).
+term(y).
+term(z).
+term(f).
+term(g).
+term(h).
+
+term(apply(M,N)) :- term(M), term(N).
+term(lambda(X,M)) :- term(X), term(M).
+
diff --git a/topics/exercises/lambda2/variables.pro b/topics/exercises/lambda2/variables.pro
@@ -0,0 +1,25 @@
+:- ['syntax.pro'].
+
+%% see slide 153
+
+free(x,[x]).
+free(y,[y]).
+free(z,[z]).
+free(f,[f]).
+free(g,[g]).
+free(h,[h]).
+
+free(apply(M,N),FV) :-
+ free(M,FV1),
+ free(N,FV2),
+ append(FV1,FV2,FV).
+
+free(lambda(X,M),FV) :-
+ free(M,FV1),
+ (
+  append(L1,[X|L2],FV1),
+  append(L1,L2,FV)
+ ;
+  FV = FV1
+ ).
+