private Stmt ParseForStatement()
{
ConsumeToken(TokenType.LEFT_PARENTHESIS, "Expect '(' after for keyword");
Stmt initializer;
if (MatchTokens(TokenType.SEMICOLON))
{
initializer = null;
}
else if (MatchTokens(TokenType.VAR))
{
initializer = ParseVarDeclaration();
}
else
{
initializer = ParseExpressionStatement();
}
Expr condition = null;
if (!CheckToken(TokenType.SEMICOLON))
{
condition = ParseExpression();
}
ConsumeToken(TokenType.SEMICOLON, "Expect ';' after for loop condition");
Expr increment = null;
if (!CheckToken(TokenType.RIGHT_PARENTHESIS))
{
increment = ParseExpression();
}
ConsumeToken(TokenType.RIGHT_PARENTHESIS, "Expect ')' after for clause");
Stmt body = ParseStatement();
if (increment != null)
{
body = new Stmt.Block(new List <Stmt>()
{
body, new Stmt.Expression(increment)
});
}
if (condition is null)
{
condition = new Expr.Literal(true);
}
body = new Stmt.While(condition, body);
if (initializer != null)
{
body = new Stmt.Block(new List <Stmt>()
{
initializer, body
});
}
return(body);
}
public object VisitBlockStmt(Stmt.Block stmt)
{
ExecuteBlock(stmt.statements, new Environment(environment));
return(null);
}