public void TestTransform()
{
ParserMonad <int> p = text => Tuple.Create(int.Parse(text.Substring(0, 5)), text.Substring(5));
var q = p.Transform(e => e * e);
q("00005wonder").AssertEquals(Tuple.Create(25, "wonder"));
}
/// <summary>
/// Returns a parser that uses the given parser to parse an intermediate parser,
/// then immediately applies that intermediate parser to the remaining text,
/// then returns the resulting value and final remaining text.
/// </summary>
public static ParserMonad <T> Flatten <T>(this ParserMonad <ParserMonad <T> > parserOfParser)
{
return(text => {
var mid = parserOfParser(text);
var parser = mid.Item1;
var remainingText = mid.Item2;
return parser(remainingText);
});
}
/// <summary>
/// Returns a parser that uses the given parser but transforms its resulting value with the given transformation.
/// </summary>
public static ParserMonad <TOut> Transform <TIn, TOut>(this ParserMonad <TIn> parser, Func <TIn, TOut> transformation)
{
return(text => {
var mid = parser(text);
var value = mid.Item1;
var remainingText = mid.Item2;
var result = transformation(value);
return Tuple.Create(result, remainingText);
});
}
public void TestFlatten()
{
ParserMonad <ParserMonad <int> > p = text => {
var first = text[0];
if (first == 'a')
{
return(Tuple.Create <ParserMonad <int>, string>(
rest => Tuple.Create(int.Parse(rest.Substring(0, 5)), rest.Substring(5)),
text.Substring(1)));
}
return(Tuple.Create(ParserMonad.Wrap(-1), text.Substring(1)));
};
var q = p.Flatten();
q("a00004x").AssertEquals(Tuple.Create(4, "x"));
q("b00004x").AssertEquals(Tuple.Create(-1, "00004x"));
}
public void TestWrap()
{
var s = ParserMonad.Wrap("test");
s("whatever").AssertEquals(Tuple.Create("test", "whatever"));
}
