/// <summary>
/// Consumes an if statement.
/// </summary>
private IfStatement IfStatement()
{
Consume(TokenType.LeftParen, "Expected '(' after 'if'.");
var condition = Expression();
Consume(TokenType.RightParen, "Expected ')' after 'if' condition.");
var thenBranch = Statement();
StatementBase elseBranch = null;
if (NextTokenMatches(TokenType.Else))
{
elseBranch = Statement();
}
return(new IfStatement(condition, thenBranch, elseBranch));
}
public IfStatement(ExpressionBase condition, StatementBase thenBranch, StatementBase elseBranch)
{
Condition = condition;
ThenBranch = thenBranch;
ElseBranch = elseBranch;
}
public WhileStatement(ExpressionBase condition, StatementBase body)
{
Condition = condition;
Body = body;
}
/// <summary>
/// Runs the statement's <see cref="StatementBase.Accept(IStatementVisitor)"/> method.
/// </summary>
/// <param name="statement">Statement to execute.</param>
private void Execute(StatementBase statement)
{
statement.Accept(this);
}
/// <summary>
/// Consumes a for statement (desugars into a block-enclosed while loop).
/// </summary>
private StatementBase ForStatement()
{
Consume(TokenType.LeftParen, "Expected '(' after 'for'.");
StatementBase initializer = null;
if (!NextTokenMatches(TokenType.SemiColon))
{
initializer = NextTokenMatches(TokenType.Var)
? VarDeclaration()
: ExpressionStatement();
}
ExpressionBase condition = null;
if (!PeekMatches(TokenType.SemiColon))
{
condition = Expression();
}
Consume(TokenType.SemiColon, "Expected ';' after for loop condition.");
ExpressionBase increment = null;
if (!PeekMatches(TokenType.RightParen))
{
increment = Expression();
}
Consume(TokenType.RightParen, "Expected ')' after for loop clauses.");
try
{
_loopDepth++;
var body = Statement();
if (increment != null)
{
// wrap the body in a block with the increment executing at the end
body = new BlockStatement(new[]
{
body,
new ExpressionStatement(increment)
});
}
// wire up a while loop using the condition and body
condition ??= new LiteralExpression(true);
body = new WhileStatement(condition, body);
if (initializer != null)
{
// wrap the body in another block with the increment executing first
body = new BlockStatement(new[]
{
initializer,
body
});
}
return(body);
}
finally
{
_loopDepth--;
}
}