completed (modulo the parser)

git-svn-id: https://slps.svn.sourceforge.net/svnroot/slps@700 ab42f6e0-554d-0410-b580-99e487e6eeb2

topics/exercises/while3/bigStm.pro

@@ -1,15 +1,19 @@
-% Big-step transition relation for statement execution
+%% Big-step transition relation for statement execution
 
+% Skip statement
 execute(skip,M,M).
 
+% Sequential composition
 execute(slist(S1,S2),M1,M3) :-
  execute(S1,M1,M2),
  execute(S2,M2,M3).
 
+% Assignment
 execute(assign(identifier(X),A),M1,M2) :-
  evala(A,M1,Y),
  update(M1,X,Y,M2).
 
+% Conditional statement
 execute(ifthenelse(B,S1,S2),M1,M2) :-
  evalb(B,M1,X),
  (
@@ -20,4 +24,15 @@ execute(ifthenelse(B,S1,S2),M1,M2) :-
   execute(S2,M1,M2)
  ).
 
+% Loop statement
+execute(while(B,S),M1,M3) :-
+ evalb(B,M1,X),
+ (
+  X == tt,
+  execute(S,M1,M2),
+  execute(while(B,S),M2,M3)
+ ;
+  X == ff,
+  M3 = M1
+ ).
 

topics/exercises/while3/compExpr.pro

@@ -1,5 +1,4 @@
 %% Evaluate arithmetic expressions
-
 % Number is evaluated to its value
 evala(number(V),_,V).
 
@@ -25,7 +24,6 @@ evala(mul(A1,A2),M,V) :-
   V is V1 * V2.
 
 %% Evaluate Boolean expressions
-
 % True is tt
 evalb(true,_,tt).
 
@@ -37,13 +35,19 @@ evalb(not(B),M,V) :-
  evalb(B,M,V1),
  not(V1,V).
 
+% Conjunction
+evalb(and(B1,B2),M,V) :-
+ evalb(B1,M,V1),
+ evalb(B2,M,V2),
+ and(V1,V2,V).
+
 % Test for equality
 evalb(equals(A1,A2),M,V) :-
   evala(A1,M,V1),
   evala(A2,M,V2),
   equals(V1,V2,V).
 
-% Test for equality
+% Test for being less than or equal
 evalb(lte(A1,A2),M,V) :-
   evala(A1,M,V1),
   evala(A2,M,V2),
@@ -56,4 +60,7 @@ lte(V1,V2,tt) :- V1 =< V2.
 lte(V1,V2,ff) :- \+ V1 =< V2.
 not(tt,ff).
 not(ff,tt).
+and(tt,tt,tt).
+and(ff,_,ff).
+and(_,ff,ff).
 

topics/exercises/while3/input.txt

@@ -1 +1,8 @@
-y:=2; if y = 3 then z := y else z := 1000
+y:=2;
+x:=(y+4);
+if (y = 2 ^ x = 6)
+ then
+  z := y
+ else
+  z := 1000;
+while x≤10 do x := (x + 1)

topics/exercises/while3/mappings.pro

@@ -4,6 +4,6 @@ lookup(M,X,Y) :- append(_,[(X,Y)|_],M).
 % Function update in one position
 update([],X,Y,[(X,Y)]).
 update([(X,_)|M],X,Y,[(X,Y)|M]).
-update([(X1,_)|M1],X2,Y2,[(X1,Y2)|M2]) :- \+ X1 = X2, update(M1,X2,Y2,M2).
+update([(X1,Y1)|M1],X2,Y2,[(X1,Y1)|M2]) :- \+ X1 = X2, update(M1,X2,Y2,M2).