+ifthenelse, +booleans

git-svn-id: https://slps.svn.sourceforge.net/svnroot/slps@692 ab42f6e0-554d-0410-b580-99e487e6eeb2

topics/exercises/while1/Parser.pro

@@ -22,11 +22,40 @@ statement(assign(identifier(V),E)) -->
  expression(E).
 
 % Conditional statement
-%  (homework)
+statement(ifthenelse(E,S1,S2)) -->
+ keyword("if"),
+ expression(E),
+ keyword("then"),
+ statement(S1),
+ keyword("else"),
+ statement(S2).
 
 % Expressions
+% Number is a an expression
 expression(number(N)) --> number(N).
 
+% Boolean primitives are expressions
+expression(true) --> keyword("true").
+expression(false) --> keyword("false").
+
+% Comparison is a boolean expression: greater than
+expression(isgreaterthan(V,E)) -->
+ identifier(V),
+ keyword(">"),
+ expression(E).
+
+% Less than
+expression(islessthan(V,E)) -->
+ identifier(V),
+ keyword("<"),
+ expression(E).
+
+% Equals
+expression(equals(V,E)) -->
+ identifier(V),
+ keyword("=="),
+ expression(E).
+
 % Dealing with spaces
 spaces --> [0' ], spaces. %'
 spaces --> [].

topics/exercises/while1/input.txt

@@ -1 +1 @@
-x:=2;y:=2
+if x == 0 then y:=2 else z:=2; skip