private Stmt ForStatement()
{
Consume(TokenType.LEFT_PAREN, "Expect '(' after 'for'.");
// If the token following the ( is a semicolon then the initializer
// has been omitted. Otherwise, we check for a var keyword to see
// if it’s a variable declaration. If neither of those matched, it
// must be an expression. We parse that and wrap it in an expression
// statement so that the initializer is always of type Stmt
Stmt initializer = Match(TokenType.SEMICOLON)
? null
: Match(TokenType.VAR)
? VarDeclaration()
: ExpressionStatement();
// If next token is a semicolon then the condition has been omitted.
Expr condition = Check(TokenType.SEMICOLON) ? null : Expression();
Consume(TokenType.SEMICOLON, "Expect ';' after loop condition.");
// If next token is closing right paren, increment ommitted.
Expr increment = Check(TokenType.RIGHT_PAREN) ? null : Expression();
Consume(TokenType.RIGHT_PAREN, "Expect ')' after for clauses.");
var body = Statement();
// Add the increment expression evaluation to end of body if not null
if (increment != null)
{
body = new Block(new List <Stmt> {
body, new Expression(increment)
});
}
// Wrap the body into a while based on condition. If null then set
// condition to true (infinite loop)
if (condition is null)
{
condition = new Literal(true);
}
body = new While(condition, body);
// If initializer was set, wrap body in block with initializer to run
// first before the loop body is executed
if (initializer != null)
{
body = new Block(new List <Stmt> {
initializer, body
});
}
return(body);
}
public string VisitWhileStmt(While stmt)
{
throw new System.NotImplementedException();
}
public object VisitWhileStmt(While stmt)
{
Resolve(stmt.Condition);
Resolve(stmt.Body);
return(null);
}