private void CompareListToPeekableEnumerator(List <string> list, IPeekableEnumerator <string> enumerator)
{
Assert.AreEqual(list[0], enumerator.PeekNext);
Assert.IsNull(enumerator.Current);
Assert.IsTrue(enumerator.MoveNext());
Assert.AreEqual(list[0], enumerator.Current);
Assert.AreEqual(list[0], ((IEnumerator)enumerator).Current);
Assert.AreEqual(list[1], enumerator.PeekNext);
Assert.IsTrue(enumerator.MoveNext());
Assert.AreEqual(list[2], enumerator.PeekNext);
Assert.AreEqual(list[1], enumerator.Current);
Assert.IsTrue(enumerator.MoveNext());
Assert.IsNull(enumerator.PeekNext);
Assert.AreEqual(list[2], enumerator.Current);
Assert.IsFalse(enumerator.MoveNext());
Assert.IsNull(enumerator.Current);
Assert.IsNull(enumerator.PeekNext);
try
{
enumerator.Reset();
Assert.IsNull(enumerator.Current);
Assert.AreEqual(list[0], enumerator.PeekNext);
Assert.IsTrue(enumerator.MoveNext());
Assert.AreEqual(list[0], enumerator.Current);
}
catch (System.NotSupportedException)
{
// ignore if enumerator.Reset() is unavailable
}
}
private IStatement ParseLetStatement(IPeekableEnumerator <Token> tokens)
{
if (ExpectTokenAndAdvance(tokens, Token.Tokens.Let) == null)
{
return(null);
}
var identifierToken = ExpectTokenAndAdvance(tokens, Token.Tokens.Ident);
if (identifierToken == null)
{
return(null);
}
var identifier = new Identifier(identifierToken.Literal);
if (ExpectTokenAndAdvance(tokens, Token.Tokens.Assign) == null)
{
return(null);
}
// TODO: parse expression
while (tokens.MoveNext())
{
if (tokens.Current.Type == Token.Tokens.Semicolon)
{
return(new LetStatement(identifier, null));
}
}
return(null);
}
private Token ExpectTokenAndAdvance(IPeekableEnumerator <Token> tokens, Token.Tokens ident)
{
var currentToken = tokens.Current;
if (currentToken?.Type != ident)
{
AddError(string.Format("expected {0}, got {1} instead",
ident,
currentToken?.ToString() ?? "<EOF>"));
return(null);
}
tokens.MoveNext();
return(currentToken);
}
private IStatement ParseExpressionStatement(IPeekableEnumerator <Token> tokens)
{
var expression = _expressionParser.ParseExpression(tokens, Precedence.Lowest);
if (expression == null)
{
return(null);
}
var statement = new ExpressionStatement(expression);
if (tokens.PeekNext?.Type == Token.Tokens.Semicolon)
{
tokens.MoveNext();
}
return(statement);
}
private IStatement ParseReturnStatement(IPeekableEnumerator <Token> tokens)
{
if (ExpectTokenAndAdvance(tokens, Token.Tokens.Return) == null)
{
return(null);
}
// TODO: parse expression
while (tokens.MoveNext())
{
if (tokens.Current.Type == Token.Tokens.Semicolon)
{
return(new ReturnStatement(null));
}
}
return(null);
}
// IEnumerator public bool MoveNext() => _with.MoveNext();