public override IMatched <Unit> Parse(ParseState state, Token[] tokens, ExpressionBuilder builder)
{
state.Colorize(tokens, Color.Whitespace, Color.Keyword);
if (builder.ToExpression().If(out var expression, out var exception))
{
var comprehensions = new List <(Symbol, Expression, IMaybe <Expression>, string)>();
if (getInnerComprehension(state).ValueOrCast <Unit>(out var tuple, out var asUnit))
{
var(comparisand, source, ifExp) = tuple;
var image = $"for {comparisand} := {source}";
comprehensions.Add((comparisand, source, ifExp, image));
}
else
{
return(asUnit);
}
while (state.More)
{
var parser = new InnerComprehensionParser(builder, comprehensions);
if (parser.Scan(state).If(out _, out var anyException))
{
}
else if (anyException.If(out exception))
{
return(failedMatch <Unit>(exception));
}
else
{
break;
}
}
var stack = new Stack <(Symbol, Expression, IMaybe <Expression>, string)>();
foreach (var item in comprehensions)
{
stack.Push(item);
}
For forStatement;
var images = new StringBuilder();
if (stack.Count > 0)
{
var(symbol, source, ifExp, image) = stack.Pop();
images.Append(image);
var yieldStatement = new Yield(expression);
var block = new Block(yieldStatement);
if (ifExp.If(out var boolean))
{
block = new Block(new If(boolean, block));
}
forStatement = new For(symbol, source, block);
}
else
{
return(notMatched <Unit>());
}
while (stack.Count > 0)
{
var(symbol, source, ifExp, image) = stack.Pop();
images.Append(image);
var block = new Block(forStatement);
if (ifExp.If(out var boolean))
{
block = new Block(new If(boolean, block));
}
forStatement = new For(symbol, source, block);
}
builder.Clear();
state.CreateReturnType();
var statements = new List <Statement>
{
forStatement, new Return(new Expression(new NoneSymbol()), state.GetReturnType())
};
state.RemoveReturnType();
builder.Add(new ComprehensionSymbol(new Block(statements), images.ToString()));
return(Unit.Matched());
}
else
{
return(failedMatch <Unit>(exception));
}
}