public static StateEither <ParserState <T>, string, T> Peek()
{
return
(from i in Index.GetS().ToStateEither <ParserState <T>, string, uint>()
from data in Data.GetS().ToStateEither <ParserState <T>, string, T[]>()
from @byte in i >= data.Length
? "Unexpected end of input sequence".InsertLeft <ParserState <T>, string, T>()
: data[i].InsertRight <ParserState <T>, string, T>()
select @byte);
}
public void LensReadTest()
{
var nameAndPosition = from name in TurtleName.GetS()
from x in TurtleX.GetS()
from y in TurtleY.GetS()
select Tuple.Create(name, x, y);
var turtle1 = new Turtle("bob", new Position(x: 10, y: -2));
var result = nameAndPosition.Eval(turtle1);
Console.WriteLine(result);
Assert.AreEqual("bob", result.Item1);
Assert.AreEqual(10, result.Item2);
Assert.AreEqual(-2, result.Item3);
}
