Node expr()
{
switch (currToken.Type)
{
case TokenType.IDE:
return ide();
case TokenType.LET:
Env savedEnv = top;
top = new Env(top);
Token letToken = match(currToken.Type);
IdeNode id = ide();
match(TokenType.EQUAL);
Node definition = expr();
top.Put(id.Token, definition.eval());
match(TokenType.IN);
Node body = expr();
LetNode let = new LetNode(letToken, id, definition, body, top);
top = savedEnv;
return let;
case TokenType.AND:
Token andToken = match(currToken.Type);
match(TokenType.OPENB);
AndNode and = new AndNode(andToken);
while (currToken.Type != TokenType.CLOSEB)
{
and.addExpression(expr());
if (currToken.Type != TokenType.CLOSEB)
match(TokenType.COMMA);
}
match(TokenType.CLOSEB);
return and;
case TokenType.BOOL:
return new Node(match(currToken.Type));
default:
Error("Error: invalid token: " + currToken.Type.ToString());
return null;
}
}
public IdeNode(Token t, Env e)
: base(t, e)
{
}
public LetNode(Token t, IdeNode ide, Node definition, Node body, Env e)
: base(t, e)
{
this.ide = ide;
this.definition = definition;
this.body = body;
}
public Node(Token t, Env e = null)
{
this.token = t;
this.env = e;
}
public Env(Env p = null)
{
table = new Hashtable();
this.prev = p;
}