/// <summary>
/// p1.Or(p2) tries p1, but if it fails without consuming input, runs p2 instead.
/// </summary>
/// <typeparam name="T">The type of result object generated.</typeparam>
/// <param name="p1">The first parser to run.</param>
/// <param name="p2">The second parser to run.</param>
/// <returns>Returns the combined parser function.</returns>
internal static P <TInput, TValue> Or <TInput, TValue>(this P <TInput, TValue> p1, P <TInput, TValue> p2)
where TInput : IComparable
{
return(input =>
{
Consumed <TInput, TValue> consumed1 = p1(input);
if (consumed1.ParseResult.Succeeded || consumed1.HasConsumedInput)
{
return consumed1;
}
else
{
Consumed <TInput, TValue> consumed2 = p2(input);
if (consumed2.HasConsumedInput)
{
return consumed2;
}
return new Consumed <TInput, TValue>(
consumed2.HasConsumedInput,
consumed2.ParseResult.MergeError(consumed1.ParseResult.ErrorInfo));
}
});
}
/// <summary>
/// This function runs parser p1 on the input. If it fails, return
/// an empty Consumed. If it succeeds, run the provided function on the result
/// of the initial function.
/// </summary>
/// <typeparam name="TValue1">The type of result object generated by the first function.</typeparam>
/// <typeparam name="TValue2">The type of result object generated by the second function.</typeparam>
/// <param name="p1">The initial parser to run.</param>
/// <param name="f">The function defining the second parser to run.</param>
/// <returns>Returns the completely constructed parser.</returns>
internal static P <TInput, TValue2> Then <TInput, TValue1, TValue2>(
this P <TInput, TValue1> p1, Func <TValue1, P <TInput, TValue2> > f)
where TInput : IComparable
{
return(input =>
{
Consumed <TInput, TValue1> consumed1 = p1(input);
if (consumed1.ParseResult.Succeeded)
{
Consumed <TInput, TValue2> consumed2 =
f(consumed1.ParseResult.Result)(consumed1.ParseResult.RemainingInput);
return new Consumed <TInput, TValue2>(
consumed1.HasConsumedInput || consumed2.HasConsumedInput,
consumed2.HasConsumedInput
? consumed2.ParseResult
: consumed2.ParseResult.MergeError(consumed1.ParseResult.ErrorInfo));
}
else
{
return new Consumed <TInput, TValue2>(
consumed1.HasConsumedInput,
new ParseResult <TInput, TValue2>(consumed1.ParseResult.ErrorInfo));
}
});
}
/// <summary>
/// p1.Or(p2) tries p1, but if it fails without consuming input, runs p2 instead.
/// </summary>
/// <typeparam name="T">The type of result object generated.</typeparam>
/// <param name="p1">The first parser to run.</param>
/// <param name="p2">The second parser to run.</param>
/// <returns>Returns the combined parser function.</returns>
internal static P <TokenTuple, T> Or <T>(this P <TokenTuple, T> p1, P <TokenTuple, T> p2)
{
return(input =>
{
Consumed <TokenTuple, T> consumed1 = p1(input);
if (consumed1.ParseResult.Succeeded || consumed1.HasConsumedInput)
{
return consumed1;
}
else
{
Consumed <TokenTuple, T> consumed2 = p2(input);
if (consumed2.HasConsumedInput)
{
return consumed2;
}
return new Consumed <TokenTuple, T>(
consumed2.HasConsumedInput,
consumed2.ParseResult.MergeError(consumed1.ParseResult.ErrorInfo));
}
});
}
/// <summary>
/// If the parse succeeded and consumed input, create a token that indicates
/// the result and contains the text and position of the consumed input.
/// If the parse was not successful, returns a default TokenTuple
/// (TokenType=None).
/// </summary>
/// <param name="newState">The state after a successful parse.</param>
/// <param name="startingState">The state before the parse began.</param>
/// <returns>Returns a TokenTuple containing the token type, text and position.</returns>
internal static TokenTuple CreateToken(this Consumed <string, TokenType> newState,
ParserState <string> startingState)
{
TokenTuple tok = default(TokenTuple);
if ((newState.HasConsumedInput) && (newState.ParseResult.Succeeded))
{
tok.TokenType = newState.ParseResult.Result;
tok.Position = startingState.Position;
tok.Text = ConstructString(newState.InputConsumedSince(startingState));
}
return(tok);
}
/// <summary>
/// Try(p) attempts to run parser p. If it fails, it pretends
/// that it hasn't consumed any input.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="p"></param>
/// <returns></returns>
internal static P <TInput, TValue> Try_ <TInput, TValue>(this P <TInput, TValue> p)
{
return(input =>
{
Consumed <TInput, TValue> consumed = p(input);
if (consumed.HasConsumedInput && !consumed.ParseResult.Succeeded)
{
return new Consumed <TInput, TValue>(false, consumed.ParseResult);
}
else
{
return consumed;
}
});
}
/// <summary>
/// This function runs parser p1 on the input. If it fails, return
/// null. If it succeeds, run the provided function on the result
/// of the initial function.
/// </summary>
/// <typeparam name="T">The type of result object generated by the first function.</typeparam>
/// <typeparam name="U">The type of result object generated by the second function.</typeparam>
/// <param name="p1">The initial parser to run.</param>
/// <param name="f">The function defining the second parser to run.</param>
/// <returns>Returns the completely constructed parser.</returns>
internal static P <TokenTuple, U> Then <T, U>(this P <TokenTuple, T> p1, Func <T, P <TokenTuple, U> > f)
{
return(input =>
{
Consumed <TokenTuple, T> consumed1 = p1(input);
if (consumed1.ParseResult.Succeeded)
{
Consumed <TokenTuple, U> consumed2 = f(consumed1.ParseResult.Result)(consumed1.ParseResult.RemainingInput);
return new Consumed <TokenTuple, U>(
consumed1.HasConsumedInput || consumed2.HasConsumedInput,
consumed2.HasConsumedInput
? consumed2.ParseResult
: consumed2.ParseResult.MergeError(consumed1.ParseResult.ErrorInfo));
}
else
{
return new Consumed <TokenTuple, U>(
consumed1.HasConsumedInput,
new ParseResult <TokenTuple, U>(consumed1.ParseResult.ErrorInfo));
}
});
}
internal List <TInput> InputConsumedSince(Consumed <TInput, TValue> previousConsumedResult)
{
return(this.ParseResult.ConsumedInputSince(previousConsumedResult.ParseResult));
}
