####### DOCUMENTATIATOIAITAT ION ########
+Files:
+Typechecker.hs: Simple modification of the bnfc-generated Testsyntax which calls the type-checking functions.
+Typecheck.hs: Contains the type-checking functions typeCheckExp, typeCheckVar and typeCheckStm and some utility functions, responsible for the entire type-checking process.
-a simple c-like language with support for if/else-statements, while-loops and the standard arithmetic (+, -, /, *) and comparison expressions (<, >, <=, >=, ==, !=). also, increase/decrease expressions (++, --) are supported.
+Abssyntax.hs, Parsyntax.y, Lexsyntax.x,ErrM.hs,Printsyntax.hs,Skelsyntax.hs: The files generated by bnfc, only modification is the removal of the Bool type in Abssyntx.hs so haskell's internal type can be used.
-data types:
-integers and booleans.
-comments:
-// and /* */ comments are allowed.
+typing rules
+++++++++++++
+(t is little tau, T is large tau, E is 'in', and + is that other symbol)
+[Eq, Neq]
+e:bool <= e1:t & e2:t
+where e is e1 Eq e2.
+[Plus, Minus, Times, Div]
+e:int <= e1:int & e2:int
+where e is e1 Plus e2.
+[Lt, ELt, Gt, EGt]
+e:bool <= e1:int & e2:int
+where e is e1 Lt e2.
-examples:
-fib
----
-int n1 = 0;
-int n2 = 1;
-int n = readInt;
+[Assignment]
-while(n-- > 0){
- int temp = n1+n2;
- n1 = n2;
- n2 = temp;
-}
-print n2;
+T+ i := e:t <= i:t E T & T+ e:t
+where the assignment is identifier i = expression e.
-tests while, decr and assignment.
+[ExpT]
+u,e:t <= e:t & u:t
+where the expression is type u expression e.
-if
---
-if (readBool) {
- if (readInt < 0)
- print true;
- else
- print false;
-}
+[ENeg]
+e:int <= e:int
-tests if and if/else.
+[ENot]
+
+e:bool <= e:bool
+
+
+[SExp, SBlock]
+
+S:NoType <= e:t
+
+
+[SIf]
+
+T+ if e then s1 else s2 <= T+ e:bool & T+ s1 & T+ s2
+
+
+[SWhile]
+
+T+ while e do s <= T+ e:bool & T+ s
+
+
+[SDecl]
+
+T+ i:t => T', i:t <= i!ET & e:t & u:t
+
+(Type u Ident i = Exp e)
-sum
----
-int n;
-int sum = 0;
-while ((n = readInt) != -1) sum = sum + n;
-print sum;
-var
----
-int a = 3;
-int b = a - 5;
-int c = a + b*7;
-bool d = a == b;
-tests simple variable operations.
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