FParsec.CSharp

FParsec.CSharp is a C# wrapper for the F# package FParsec. FParsec is a parser combinator library with which you can implement parsers declaratively.

Why FParsec.CSharp?

While using FParsec from C# is entirely possible in theory, it is very awkward in practice. Most of FParsec's elegance is lost in translation due to C#'s inferior type inference and its lack of custom operators.

FParsec.CSharp tries to alleviate that by wrapping FParsec's operators as extension functions.

FParsec.CSharp does not try to hide any types from FParsec or FSharp.Core--the wrapper is thin and also avoids name collisions. That way you can always fallback to FParsec anytime you need some functionality not implemented by FParsec.CSharp.

Based on the current implementation it should be easy to extend the wrapper yourself if needed. Pull requests are always welcome!

Note that the documentation assumes prior knowledge on FParsec or other parser combinator libraries.

Getting started

Import the combinators, pre-defined parsers, and helper functions:

using FParsec.CSharp; // extension functions (combinators & helpers)
using static FParsec.CSharp.PrimitivesCS; // combinator functions
using static FParsec.CSharp.CharParsersCS; // pre-defined parsers

Now you can write some parsers:

var parser = AnyChar.And(Digit);
var reply = parser.ParseString("a1");
Debug.Assert(reply.Result == ('a', '1'));

Executing parsers

An FParsec parser is a function that takes a CharStream<T> and returns a Reply<T>. In C# such parsers are represented by the type FSharpFunction<CharStream<TUserState>, Reply<TResult>> and can be executed with the method Reply<TResult>> Invoke(CharStream<TUserState>).

FParsec.CSharp comes with extensions to make things easier for you.

Running the parser function and getting the `Reply`

You have already seen one way to execute a parser in the previous section: ParseString().

ParseString(string) is just a wrapper for FSharpFunc<CharStream<Unit>, Reply<T>>.Invoke(). It constructs the CharStream for you from the given string.

ParseFile(string) will do the same for a given file path.

If you need maximum control then Parse(CharStream<Unit>) is your best option. You can configure the CharStream yourself and inspect all the details of the Reply after parsing.

Getting nicer error messages with `ParserResult`

Using Invoke(), Parse(), or any of its variants is generally not recommended. FParsec provides a better way to execute parsers that generates nicely formatted error messages: Run().

The extension ParserResult<T, Unit> Run(string) does the same as Reply<T> ParseString(string), but also builds an error message from the Reply's errors and the parser postion:

var result = Many1(Digit).AndR(Upper).Run("123a");

// Don't be shocked: in the next section we will learn how to improve this.
var msg = ((ParserResult<char, Unit>.Failure)result).Item1;

Console.WriteLine(msg);

The above will print the following detailed parsing failure message:

Error in Ln: 1 Col: 4
123a
   ^
Expecting: decimal digit or uppercase letter

Run(string) is actually just a short form for RunOnString(string).

Additionally, there are three more Run...() functions: RunOnString(string, int, int) (parse a substring), RunOnStream() (parse a Stream), and RunOnFile() (parse... well you get the idea).

Handling parser results

FParsec's ParserResult is an F# discriminated union, which are awkward to work with in C#. FParsec.CSharp comes with extensions methods that hide those ugly details.

Getting the result or an exception

The easiest way to get the parser result is to use GetResult():

var one = Digit.Run("1").GetResult();
Debug.Assert(one == '1');

GetResult() will throw an InvalidOperationException in case the parser failed. The exception will contain the detailed parsing failure message.

Getting the result with custom error handling

If you need more graceful error handling you can use GetResult<T>(Func<string, T>) which delegates error handling to the caller and provides the failure message to it:

// provide fallback value
var d1 = Digit.Run("a").GetResult(_ => default);
Debug.Assert(d1 == '\0');

// throw your own exception
var d2 = Digit.Run("a").GetResult(msg => throw new Exception($"whoops... {msg}"));

// do anything as long as you return a fallback value or throw
var d3 = Digit.Run("a").GetResult(_ => {
    Console.WriteLine("oof");
    return GetRandomChar();
});

Additionally, the extensions GetResultOrError<T>(Func<ParserError, T>) and GetResultOrFailure<T>(Func<ParserResult<T, Unit>.Failure, T>) let you inspect the ParserError or Failure objects during error handling.

Safe unwrapping

Alternatively, you can can safely unwrap a ParserResult<T, Unit> into a tuple (T? result, string? message) using UnwrapResult() (which will never throw):

var (res, msg) = Digit.Run("a").UnwrapResult();
Console.WriteLine(msg ?? $"Parser succeeded: {res}");

In case parsing succeeded the left side of the tuple will hold the parser's return value and the right side will be null.

In case parsing failed the left side of the tuple will hold the return value type's default value and the right side will hold the detailed parser error message.

Hence the safest way to check if the parser result tuple indicates failure is to check whether the right side is null.

With C# 8.0 you can do that quite nicely using a switch expression and recursive patterns:

var response = Digit.Run("a").UnwrapResult() switch {
    (var r, null) => $"Parser succeeded: {r}",
    (_,    var m) => $"Parser failed: {m}"
};

UnwrapWithError() and UnwrapWithFailure() work the same way, but return the ParserError or ParserResult<TResult, Unit>.Failure instance in the right side of the tuple.

Deconstructing parser results (C# 8.0)

FParsec.CSharp extends the types involved with parser results with deconstructors so you can make use of C# 8.0's recursive patterns inside switch statements/expressions:

var response = Digit.Run("1") switch {
    ParserResult<char, Unit>.Success(var c, _, _) => $"Parsed '{c}'.",
    ParserResult<char, Unit>.Failure(_, (_, (_, _, var col, _)), _) => $"Some error at column {col}."
};

var response = Digit.ParseString("a") switch {
    (ReplyStatus.Ok, var c, _) => $"Parsed '{c}'.",
    (ReplyStatus.Error, _, (ErrorMessage.Expected err, _)) => $"Expected a {err.Label}.",
    _ => "oof."
};

You will need to import some of FParsec's namespaces for this to work:

using FParsec; // contains `ReplyStatus` and `ErrorMessage`
using static FParsec.CharParsers; // contains `ParserResult`

Working with user state

FParsec.CSharp, like FParsec, supports parsing with user state. This is reflected by the type parameter U in the signatures:

public FSharpFunc<CharStream<U>, Reply<(T1, T2)>> And<U, T1, T2>(
    this FSharpFunc<CharStream<U>, Reply<T1>> p1,
    FSharpFunc<CharStream<U>, Reply<T2>> p2);

If a combinator/parser supports user state then it will always have U as the first type parameter.

For the combinators from FParsec.CSharp.PrimitivesCS this will be transparent most of the time, because C# is able to infer the user state type of the combinator from the user state type of the parser argument(s).

Unfortunately C# is not able to infer the user state type retrospectively from later bindings and hence forces you to explicitly specify the user state type on parsers that have no parser parameters. In the case of the predefined parsers from FParsec.CSharp.CharParsersCS (which usually don't take other parsers as arguments) this restriction would be cause for much annoyance.

That's why all parsers/combinators that have no parser parameters have two variants: one assuming a user state type of Unit and another one expecting the explicit type argument U. The names of the latter ones are always suffixed with the letter "U":

var parserWithoutUserState = Digit.And(Letter);

var parserWithUserState = DigitU<int>().And(LetterU<int>());

Below are example test cases to demonstrate working with user state:

[Fact] public void SimpleSet() {
    switch (SetUserState(12).RunOnString("", 0)) {
        case ParserResult<Unit, int>.Success(_, 12, _):
            break;
        default:
            throw new Exception();
    }
}

[Fact] public void CountParsedLetters() {
    var countedLetter = LetterU<int>().And(UpdateUserState<int>(cnt => cnt + 1));

    SkipMany(countedLetter).And(GetUserState<int>())
    .RunOnString("abcd", 0).GetResult()
    .ShouldBe(4);
}

[Fact] public void CheckNestingLevel() {
    FSharpFunc<CharStream<int>, Reply<Unit>> expr = null;
    var parens = Between('(', Rec(() => expr), ')');
    var empty = ReturnU<int, Unit>(null);
    expr = Choice(
        parens.AndR(UpdateUserState<int>(depth => depth + 1)),
        empty);

    expr.AndR(UserStateSatisfies<int>(depth => depth < 3))
    .RunOnString("((()))", 0)
    .IsFailure
    .ShouldBeTrue();
}

Using FParsec.CSharp and FParsec together

Working with FParsec parsers directly

In case you need one of FParsec's more specialized parsers you can easily import their namespace:

using static FParsec.CharParsers;

In the example below we are using FParsec.CharParsers.many1Chars2(). As you can see it integrates seemlessly with FParsec.CSharp:

var first = Letter.Or(CharP('_'));
var rest = Letter.Or(CharP('_')).Or(Digit);
var identifier = many1Chars2(first, rest);
var p = identifier.And(Skip('=')).And(Int);

var r = p.ParseString("my_1st_var=13");

System.Diagnostics.Debug.Assert(r.Result == ("my_1st_var", 13));

Passing lambdas to FParsec

Some of FParsec's parsers take anonymous functions. But since they expect curried FSharpFuncs they won't accept C# lambdas. FParsec.CSharp comes with a little helper to create FSharpFuncs from Func objects:

// convert lambda with factory method
var fsfunc1 = FSharpFunc.From<char, bool>(c => c == 'x' || c == 'y');

// convert Func object with extension method
Func<char, bool> func = c => c == '1' || c == '2';
var fsfunc2 = func.ToFSharpFunc();

var p = manySatisfy<Unit>(fsfunc1).And(manySatisfy<Unit>(fsfunc2));

var r = p.ParseString("xyxyyy212221212");

Examples

You can find lots of examples in the test project. Below are some parser definitions from there.

Simple JSON

FSharpFunc<CharStream<Unit>, Reply<JToken>> jvalue = null;

var jnull = StringCI("null", (JToken)null).Lbl("null");

var jnum = Float.Map(i => (JToken)i).Lbl("number");

var jbool = StringCI("true").Or(StringCI("false"))
    .Map(b => (JToken)bool.Parse(b))
    .Lbl("bool");

var quotedString = Between('"', ManyChars(NoneOf("\"")), '"');

var jstring = quotedString.Map(s => (JToken)s).Lbl("string");

var arrItems = Many(Rec(() => jvalue), sep: CharP(',').And(WS));
var jarray = Between(CharP('[').And(WS), arrItems, CharP(']'))
    .Map(elems => (JToken)new JArray(elems))
    .Lbl("array");

var jidentifier = quotedString.Lbl("identifier");
var jprop = jidentifier.And(WS).And(Skip(':')).And(WS).And(Rec(() => jvalue))
    .Map((name, value) => new JProperty(name, value));
var objProps = Many(jprop, sep: CharP(',').And(WS));
var jobject = Between(CharP('{').And(WS), objProps, CharP('}'))
    .Map(props => (JToken)new JObject(props))
    .Lbl("object");

jvalue = Choice(jnum, jbool, jnull, jstring, jarray, jobject).And(WS);

var simpleJsonParser = WS.And(jobject).And(WS).And(EOF).Map(o => (JObject)o);

Simple XML

var nameStart = Choice(Letter, CharP('_'));
var nameChar = Choice(Letter, Digit, AnyOf("-_."));
var name = Many1Chars(nameStart, nameChar).And(WS);

var quotedString = Between('"', ManyChars(NoneOf("\"")), '"');
var attribute = name.And(Skip('=')).And(WS).And(quotedString).And(WS)
    .Lbl_("attribute")
    .Map((attrName, attrVal) => new XAttribute(attrName, attrVal));
var attributes = Many(attribute);

FSharpFunc<CharStream<Unit>,Reply<XElement>> element = null;

var elementStart = Skip('<').AndTry(name.Lbl("tag name")).And(attributes);

FSharpFunc<CharStream<Unit>, Reply<string>> closingTag(string tagName) => Between("</", StringP(tagName).And(WS), ">")
    .Lbl_($"closing tag '</{tagName}>'");

FSharpFunc<CharStream<Unit>, Reply<object>> textContent(string leadingWS) => NotEmpty(ManyChars(NoneOf("<"))
    .Map(text => leadingWS + text)
    .Map(x => (object)x)
    .Lbl_("text content"));

var childElement = Rec(() => element).Map(x => (object)x).Lbl_("child element");

object EmptyContentToEmptyString(FSharpList<object> xs) => xs.IsEmpty ? (object)"" : xs;

var elementContent = Many(WS.WithSkipped().AndTry(ws => Choice(textContent(ws), childElement)))
    .Map(EmptyContentToEmptyString);

FSharpFunc<CharStream<Unit>,Reply<XElement>> elementEnd(string elName, FSharpList<XAttribute> elAttrs) =>
    Choice(
        Skip("/>").Return((object)null),
        Skip(">").And(elementContent).And(WS).AndL(closingTag(elName)))
    .Map(elContent => new XElement(elName, elContent, elAttrs));

element = elementStart.And(elementEnd);

var simpleXmlParser = WS.And(element).And(WS).And(EOF);

Glob patterns

var globParser =
    Many(Choice(
        Skip('?').Map(NFA.MakeAnyChar),
        Skip('*').Map(NFA.MakeAnyChar).Map(NFA.MakeZeroOrMore),
        Between('[', AnyChar.And(Skip('-')).And(AnyChar), ']').Map(NFA.MakeCharRange),
        Skip('\\').And(AnyOf(@"?*[]\")).Map(NFA.MakeChar),
        AnyChar.Map(NFA.MakeChar)))
    .And(EOF)
    .Map(NFA.Concat)
    .Map(proto => proto(new Final()));

This example contructs a non-deterministic finite automaton (NFA) during parsing and can be used for matching:

[Fact] public void CanParseAndMatchGlobPattern() => globParser
    .ParseString("The * syntax is easy?").Result
    .Matches("The glob syntax is easy!")
    .ShouldBe(true);

Arithmetic expressions

FParsec.CSharp comes with a builder to construct FParsec.OperatorPrecedenceParsers:

var basicExprParser = new OPPBuilder<Unit, int, Unit>()
    .WithOperators(ops => ops
        .AddInfix("+", 1, (x, y) => x + y)
        .AddInfix("*", 2, (x, y) => x * y))
    .WithTerms(Natural)
    .Build()
    .ExpressionParser;

var recursiveExprParser = new OPPBuilder<Unit, int, Unit>()
    .WithOperators(ops => ops
        .AddInfix("+", 1, (x, y) => x + y)
        .AddInfix("*", 2, (x, y) => x * y))
    .WithTerms(term => Choice(Natural, Between('(', term, ')')))
    .Build()
    .ExpressionParser;

It also supports implicit operators:

var exprParser =
    WS.And(new OPPBuilder<Unit, int, Unit>()
        .WithOperators(ops => ops
            .AddInfix("+", 10, WS, (x, y) => x + y)
            .AddInfix("-", 10, WS, (x, y) => x - y)
            .AddInfix("*", 20, WS, (x, y) => x * y)
            .AddInfix("/", 20, WS, (x, y) => x / y)
            .AddPrefix("-", 20, x => -x)
            .AddInfix("^", 30, Associativity.Right, WS, (x, y) => (int)Math.Pow(x, y))
            .AddPostfix("!", 40, Factorial))
        .WithImplicitOperator(20, (x, y) => x * y)
        .WithTerms(term => Choice(
            Natural.And(WS),
            Between(CharP('(').And(WS), term, CharP(')').And(WS))))
        .Build()
        .ExpressionParser);

Simple regular expressions

Armed with the OPPBuilder and the NFA implementation used for the glob parser above we can even build a simple regex parser & matcher:

var simpleRegexParser =
    Many(new OPPBuilder<Unit, NFA.ProtoState, Unit>()
        .WithImplicitOperator(2, NFA.Connect)
        .WithOperators(ops => ops
            .AddPostfix("*", 3, NFA.MakeZeroOrMore)
            .AddPostfix("+", 3, NFA.MakeOneOrMore)
            .AddPostfix("?", 3, NFA.MakeZeroOrOne)
            .AddInfix("|", 1, NFA.MakeAlternation))
        .WithTerms(matchExpr => {
            var group = Between('(', Many(matchExpr), ')');
            var wildcard = Skip('.');
            var charMatch = NoneOf("*+?|()");
            return Choice(
                group.Map(NFA.Concat),
                wildcard.Map(NFA.MakeAnyChar),
                charMatch.Map(NFA.MakeChar));
        })
        .Build()
        .ExpressionParser)
    .And(EOF)
    .Map(NFA.Concat)
    .Map(proto => proto(new Final()));

[Fact] public void CanParseAndMatchRegex() => simpleRegexParser
    .ParseString("The( simple)? .+ syntax is .*more tricky( and (complex|difficult|involved))+.").Result
    .Matches("The simple regex syntax is only a little bit more tricky and complex and involved!")
    .ShouldBe(true);

Simple script language

This example implements a simple functional script language. It only knows one type (int) and is super inefficient, but it has lots of functional fu (e.g. lazy evaluation, partial application, lambdas, higher order functions, and function composition).

var number = Natural.Lbl("number");

static StringParser notReserved(string id) => id == "let" || id == "in" || id == "match" ? Zero<string>() : Return(id);
var identifier1 = Choice(Letter, CharP('_'));
var identifierRest = Choice(Letter, CharP('_'), CharP('\''), Digit);
var identifier = Purify(Many1Chars(identifier1, identifierRest)).AndTry(notReserved).Lbl("identifier");

var parameters = Many(identifier, sep: WS1, canEndWithSep: true).Lbl("parameter list");

ScriptParser? expression = null;

var letBinding =
    Skip("let").AndR(WS1)
    .And(identifier).And(WS)
    .And(parameters)
    .And(Skip('=')).And(WS)
    .And(Rec(() => expression).Lbl("'let' definition expression"))
    .And(Skip("in")).And(WS1)
    .And(Rec(() => expression).Lbl("'let' body expression"))
    .Map(Flat)
    .Lbl("'let' binding");

var lambda =
    Skip('\\')
    .And(parameters)
    .And(Skip("->")).And(WS)
    .And(Rec(() => expression).Lbl("lambda body"))
    .Lbl("lambda");

var defaultCase = Skip('_').AndRTry(NotFollowedBy(identifierRest)).AndR(WS).Return(ScriptB.AlwaysMatches);
var caseValueExpr = Rec(() => expression).Map(ScriptB.Matches);
var caseExpr =
    Skip('|').AndR(WS)
    .And(defaultCase.Or(caseValueExpr).Lbl("case value expression"))
    .And(Skip("=>")).And(WS)
    .And(Rec(() => expression).Lbl("case result expression"))
    .Lbl("match case");
var matchExpr =
    Skip("match").AndR(WS1)
    .And(Rec(() => expression).Lbl("match value expression"))
    .And(Many1(caseExpr))
    .Lbl("'match' expression");

expression = new OPPBuilder<Unit, Script, Unit>()
    .WithOperators(ops => ops
        .AddInfix("+", 10, WS, ScriptB.Lift2((x, y) => x + y))
        .AddInfix("-", 10, WS, ScriptB.Lift2((x, y) => x - y))
        .AddInfix("*", 20, WS, ScriptB.Lift2((x, y) => x * y))
        .AddInfix("/", 20, WS, ScriptB.Lift2((x, y) => x / y))
        .AddInfix("%", 20, WS, ScriptB.Lift2((x, y) => x % y))
        .AddPrefix("-", 20, ScriptB.Lift(x => -x))
        .AddInfix(".", 30, Associativity.Right, WS, ScriptB.Compose))
    .WithImplicitOperator(50, ScriptB.Apply)
    .WithTerms(term =>
        Choice(
            letBinding.Map(ScriptB.BindVar),
            matchExpr.Map(ScriptB.Match),
            Between(CharP('(').And(WS), term, CharP(')').And(WS)),
            number.And(WS).Map(ScriptB.Return),
            identifier.And(WS).Map(ScriptB.Resolve),
            lambda.Map(ScriptB.Lambda))
        .Lbl("expression"))
    .Build()
    .ExpressionParser;

var scriptParser = WS.And(expression).And(EOF);

This parser builds a function that can be invoked (with an empty arguments list and an empty "runtime environment") to execute the script:

[Fact] public void FibonacciNumber() => scriptParser
    .Run(@"
        let fib n = match n
            | 0 => 0
            | 1 => 1
            | _ => fib (n-1) + fib (n-2)
        in fib 7")
    .GetResult()
    .Invoke(FSharpList<Script>.Empty, new Dictionary<string, Script>())
    .ShouldBe(13);

Hints

Debugging

When you need to debug into your parser chain, use the Debug() combinator on any of your chain's parsers.

It takes two Actions:

Action<CharStream<Unit>> before: is run before the parser is applied,
Action<CharStream<Unit>, Reply<T>> after: is run after the parser was applied.

For instance, you can use empty Actions and place break points inside them:

var p = Digit.Debug(cs => {}, (cs, r) => {})
        .And(
            Letter.Debug(cs => {}, (cs, r) => {}))
        .Debug(cs => {}, (cs, r) => {});

Reducing namespace noise

The signatures of FParsec.CSharp's combinators can look pretty daunting. For instance, the signature of the combinator Many() might appear like this in InteliSense or when hovering over its name:

Microsoft.FSharp.Core.FSharpFunc<FParsec.CharStream<Unit>, FParsec.Reply<Microsoft.FSharp.Collections.FSharpList<T>>> PrimitivesCS.Many<U, T>(Microsoft.FSharp.Core.FSharpFunc<FParsec.CharStream<Unit>, FParsec.Reply<T>> p)

Remember that Visual Studio hides namespaces in the UI that have a using in the current file. So if you add the following usings (even though not all of them are actually needed)...

using FParsec;
using Microsoft.FSharp.Collections;
using Microsoft.FSharp.Core;

...then the Visual Studio UI will simplify the above signature to:

FSharpFunc<CharStream<Unit>, Reply<FSharpList<T>>> PrimitivesCS.Many<U, T>(FSharpFunc<CharStream<Unit>, Reply<T>> p)

Still a mouthful, but a little more readable nonetheless.

Aliasing awkward types

You can use type aliases to further simplify signatures in the Visual Studio UI and your code:

using Chars = FParsec.CharStream<Microsoft.FSharp.Core.Unit>;

Unfortunately C# does not support type aliases with open generics. Hence if you want to simplify the type of a parser you will have to do it for each of the possible Reply<T>s you are using:

using StringParser = Microsoft.FSharp.Core.FSharpFunc<FParsec.CharStream<Microsoft.FSharp.Core.Unit>, FParsec.Reply<string>>;
using JsonParser = Microsoft.FSharp.Core.FSharpFunc<FParsec.CharStream<Microsoft.FSharp.Core.Unit>, FParsec.Reply<JObject>>;
// ...

If you place your import usings outside, and your alias usings inside your namespace declaration then this will simplify your alias definitions:

using System.Xml.Linq;
using FParsec;
using Microsoft.FSharp.Core;

namespace Tests
{
    using XElParser = FSharpFunc<CharStream<Unit>, Reply<XElement>>;
    // ...

Combining all suggestions your usings could look like this for minimal noise:

#pragma warning disable IDE0065 // Misplaced using directive
using FParsec;
using FParsec.CSharp;
using Microsoft.FSharp.Collections;
using Microsoft.FSharp.Core;
using static FParsec.CSharp.PrimitivesCS;
using static FParsec.CSharp.CharParsersCS;

namespace MyParser
{
    using Chars = CharStream<Unit>;
    using CharParser = FSharpFunc<CharStream<Unit>, Reply<char>>;
    using StringParser = FSharpFunc<CharStream<Unit>, Reply<string>>;
    // ...

Where is the FParsec function `x`?

FParsec.CSharp does not mirror all of FParsec's functions exactly. A few are not wrapped and some are just named differently.

Below is a table that maps FParsec's parser functions, combinators, and helper functions to their FParsec.CSharp equivalent.

The type FSharpFunc<CharStream<U>, Reply<T>> is shortened to P<T> for brewity.

Keep in mind that many predefined parsers and some of the combinators have a variant that supports parsing with user state. Those variants always have a U suffix in their name and are not listed in this table.

FParsec	FParsec.CSharp
`preturn`	`P<T> Return(T)`
`pzero`	`P<T> Zero<T>()`
`(>>=)`	`P<TR> P<T1>.And(Func<T1, P<TR>>)`, `P<TR> P<Unit>.And(Func<P<TR>>)` if left side returns `Unit`, `P<TR> P<(T1,T2)>.And(Func<T1, T2, P<TR>>)` deconstructs left tuple result, `P<TR> P<(T1,T2,T3)>.And(Func<T1, T2, T3, P<TR>>)` deconstructs left 3-tuple result
`(>>%)`	`P<T2> P<T1>.Return(T2)`
`(>>.)`	`P<T2> P<T1>.AndR(P<T2>)` skips left explicitly, `P<T> P<Unit>.And(P<T>)` skips left implicitly when it returns `Unit`
`(.>>)`	`P<T1> P<T1>.AndL(P<T2>)` skips right explicitly, `P<T> P<T>.And(P<Unit>)` skips right implicitly when it returns `Unit`
`(.>>.)`	`P<(T1,T2)> P<T1>.And(P<T2>)` if neither side returns `Unit`, `P<(Unit,Unit)> P<Unit>.And_(P<Unit>)` if any side returns `Unit`
`(\|>>)`	`P<TR> P<T1>.Map(Func<T1, TR>)`, `P<TR> P<Unit>.Map(Func<TR>)` if left side returns `Unit`, `P<TR> P<(T1,T2)>.Map(Func<T1, T2, TR>)` deconstructs left tuple result, `P<TR> P<(T1,T2,T3)>.Map(Func<T1, T2, T3, TR>)` deconstructs left 3-tuple result
`between`	`P<T2> Between(P<T1>, P<T2>, P<T3>)` (different argument order)
`pipe2`	`P<TR> Pipe(P<T1>, P<T2>, Func<T1, T2, TR>)`
`pipe3`	`P<TR> Pipe(P<T1>, P<T2>, P<T3>, Func<T1, T2, T3, TR>)`
`pipe4`	`P<TR> Pipe(P<T1>, P<T2>, P<T3>, P<T4>, Func<T1, T2, T3, T4, TR>)`
`pipe5`	`P<TR> Pipe(P<T1>, P<T2>, P<T3>, P<T4>, P<T5>, Func<T1, T2, T3, T4, T5, TR>)`
`(<\|>)`	`P<T> P<T>.Or(P<T>)`
`choice`	`P<T> Choice(params P<T>[])`
`choiceL`	`P<T> Choice(string, params P<T>[])`
`(<\|>%)`	`P<T> P<T>.Or(T)`
`opt`	`P<FSharpOption<T>> Opt_(P<T>)`, `P<T> Opt(P<T>)` unwraps the `FSharpOption<T>`, `P<T> Opt(P<T>, T)` unwraps the `FSharpOption<T>` with default value
`optional`	`P<Unit> Optional(P<T>)`
`attempt`	`P<T> Try(P<T>)`
`(>>=?)`	`P<T2> P<T1>.AndTry(Func<T1, P<T2>>)`
`(>>?)`	`P<T2> P<T1>.AndRTry(P<T2>)` skips left explicitly, `P<T> P<Unit>.AndTry(P<T>)` skips left implicitly when it returns `Unit`
`(.>>?)`	`P<T1> P<T1>.AndLTry(P<T2>)` skips right explicitly, `P<T> P<T>.AndTry(P<Unit>)` skips right implicitly when it returns `Unit`
`(.>>.?)`	`P<(T1,T2)> P<T1>.AndTry(P<T2>)` if neither side returns `Unit`, `P<(Unit,Unit)> P<Unit>.AndTry_(P<Unit>)` if any side returns `Unit`
`notEmpty`	`P<T> NotEmpty(P<T>)`
`followedBy`	`P<Unit> FollowedBy(P<T>)`
`followedByL`	`P<Unit> FollowedBy(P<T>, string)`
`notFollowedBy`	`P<Unit> NotFollowedBy(P<T>)`
`notFollowedByL`	`P<Unit> NotFollowedBy(P<T>, string)`
`lookAhead`	`P<T> LookAhead(P<T>)`
`(<?>)`	`P<T> P<T>.Label(string)`
`(<??>)`	`P<T> P<T>.Label_(string)`
`fail`	`P<T> Fail(string)`
`failFatally`	`P<T> FailFatally(string)`
`tuple2`	`P<(T1,T2)> Tuple(P<T1>, P<T2>)`
`tuple3`	`P<(T1,T2,T3)> Tuple(P<T1>, P<T2>, P<T3>)`
`tuple4`	`P<(T1,T2,T3,T4)> Tuple(P<T1>, P<T2>, P<T3>, P<T4>)`
`tuple5`	`P<(T1,T2,T3,T4,T5)> Tuple(P<T1>, P<T2>, P<T3>, P<T4>, P<T5>)`
`parray`	`P<T[]> Array(int, P<T>)`
`skipArray`	`P<Unit> SkipArray(int, P<T>)`
`many`	`P<FSharpList<T>> Many(P<T>)`
`skipMany`	`P<Unit> SkipMany(P<T>)`
`many1`	`P<FSharpList<T>> Many1(P<T>)`
`skipMany1`	`P<Unit> SkipMany1(P<T>)`
`sepBy`	`P<FSharpList<T>> Many(P<T>, P<TSep>)`
`skipSepBy`	`P<Unit> SkipMany(P<T>, P<TSep>)`
`sepBy1`	`P<FSharpList<T>> Many1(P<T>, P<TSep>)`
`skipSepBy1`	`P<Unit> SkipMany1(P<T>, P<TSep>)`
`sepEndBy`	`P<FSharpList<T>> Many(P<T>, P<TSep>, canEndWithSep: true)`
`skipSepEndBy`	`P<Unit> SkipMany(P<T>, P<TSep>, canEndWithSep: true)`
`sepEndBy1`	`P<FSharpList<T>> Many1(P<T>, P<TSep>, canEndWithSep: true)`
`skipSepEndBy1`	`P<Unit> SkipMany1(P<T>, P<TSep>, canEndWithSep: true)`
`manyTill`	`P<FSharpList<T>> ManyTill(P<T>, P<TEnd>)`
`skipManyTill`	`P<Unit> SkipManyTill(P<T>, P<TEnd>)`
`many1Till`	`P<FSharpList<T>> Many1Till(P<T>, P<TEnd>)`
`skipMany1Till`	`P<Unit> SkipMany1Till(P<T>, P<TEnd>)`
`chainl1`	`P<T> ChainL(P<T>, P<Func<T, T, T>>)`
`chainl`	`P<T> ChainL(P<T>, P<Func<T, T, T>>, T)`
`chainr1`	`P<T> ChainR(P<T>, P<Func<T, T, T>>)`
`chainr`	`P<T> ChainR(P<T>, P<Func<T, T, T>>, T)`
`runParserOnString`	`ParserResult<T> P<T>.RunOnString(string, string)`
`runParserOnSubstring`	`ParserResult<T> P<T>.RunOnString(string, int, int, string)`
`runParserOnStream`	`ParserResult<T> P<T>.RunOnStream(Stream, Encoding, string)`
`runParserOnFile`	`ParserResult<T> P<T>.RunOnFile(string, Encoding)`
`run`	`ParserResult<T> P<T>.Run(string)`
`getPosition`	`P<Position> PositionP`
`getUserState`	`P<U> GetUserState<U>()`
`setUserState`	`P<Unit> SetUserState<U>(U)`
`updateUserState`	`P<Unit> UpdateUserState<U>(Func<U, U>)`
`userStateSatisfies`	`P<Unit> UserStateSatisfies<U>(Func<U, bool>)`
`pchar`	`P<char> CharP(char)`
`skipChar`	`P<Unit> Skip(char)`
`charReturn`	`P<T> CharP(char, T)`
`anyChar`	`P<char> AnyChar`
`skipAnyChar`	`P<Unit> SkipAnyChar`
`satisfy`	`P<char> CharP(Func<char, bool>)`
`skipSatisfy`	`P<Unit> Skip(Func<char, bool>)`
`satisfyL`	`P<char> CharP(Func<char, bool>, string)`
`skipSatisfyL`	`P<Unit> Skip(Func<char, bool>, string)`
`anyOf`	`P<char> AnyOf(IEnumerable<char>)`
`skipAnyOf`	`P<Unit> SkipAnyOf(IEnumerable<char>)`
`noneOf`	`P<char> NoneOf(IEnumerable<char>)`
`skipNoneOf`	`P<Unit> SkipNoneOf(IEnumerable<char>)`
`asciiUpper`	`P<char> AsciiUpper`
`asciiLower`	`P<char> AsciiLower`
`asciiLetter`	`P<char> AsciiLetter`
`upper`	`P<char> Upper`
`lower`	`P<char> Lower`
`letter`	`P<char> Letter`
`digit`	`P<char> Digit`
`hex`	`P<char> Hex`
`octal`	`P<char> Octal`
`isAnyOf`	not implemented
`isNoneOf`	not implemented
`isAsciiUpper`	`bool IsAsciiUpper(char)`
`isAsciiLower`	`bool IsAsciiLower(char)`
`isAsciiLetter`	`bool IsAsciiLetter(char)`
`isUpper`	`bool IsUpper(char)`
`isLower`	`bool IsLower(char)`
`isLetter`	`bool IsLetter(char)`
`isDigit`	`bool IsDigit(char)`
`isHex`	`bool IsHex(char)`
`isOctal`	`bool IsOctal(char)`
`tab`	`P<char> Tab`
`newline`	`P<char> Newline`
`skipNewline`	`P<Unit> SkipNewline`
`newlineReturn`	`P<T> NewlineReturn(T)`
`unicodeNewline`	`P<Unit> UnicodeNewline`
`skipUnicodeNewline`	`P<Unit> SkipUnicodeNewline`
`unicodeNewlineReturn`	`P<T> UnicodeNewlineReturn(T x)`
`spaces`	`P<Unit> Spaces`
`spaces1`	`P<Unit> Spaces1`
`unicodeSpaces`	`P<Unit> UnicodeSpaces`
`unicodeSpaces1`	`P<Unit> UnicodeSpaces1`
`eof`	`P<Unit> EOF`
`pstring`	`P<string> StringP(string)`
`skipString`	`P<Unit> Skip(string)`
`stringReturn`	`P<T> StringP(string, T)`
`pstringCI`	`P<string> StringCI(string)`
`skipStringCI`	`P<Unit> SkipCI(string)`
`stringCIReturn`	`P<T> StringP(string, T)`
`anyString`	`P<string> AnyString(int)`
`skipAnyString`	`P<Unit> SkipAnyString(int)`
`restOfLine`	`P<string> RestOfLine(bool)`
`skipRestOfLine`	`P<Unit> SkipRestOfLine(bool)`
`charsTillString`	`Reply<string> CharsTillString(string, int, bool)`
`skipCharsTillString`	`Reply<Unit> SkipCharsTillString(string, int, bool)`
`charsTillStringCI`	`Reply<string> CharsTillStringCI(string, int, bool)`
`skipCharsTillStringCI`	`Reply<Unit> SkipCharsTillStringCI(string, int, bool)`
`manySatisfy`	`P<string> ManyChars(Func<char, bool>)`
`manySatisfy2`	`P<string> ManyChars(Func<char, bool>, Func<char, bool>)`
`skipManySatisfy`	`P<Unit> SkipManyChars(Func<char, bool>)`
`skipManySatisfy2`	`P<Unit> SkipManyChars(Func<char, bool>, Func<char, bool>)`
`many1Satisfy`	`P<string> Many1Chars(Func<char, bool>)`
`many1Satisfy2`	`P<string> Many1Chars(Func<char, bool>, Func<char, bool>)`
`skipMany1Satisfy`	`P<Unit> SkipMany1Chars(Func<char, bool>)`
`skipMany1Satisfy2`	`P<Unit> SkipMany1Chars(Func<char, bool>, Func<char, bool>)`
`many1SatisfyL`	`P<string> Many1Chars(Func<char, bool>, string)`
`many1Satisfy2L`	`P<string> Many1Chars(Func<char, bool>, Func<char, bool>, string)`
`skipMany1SatisfyL`	`P<Unit> SkipMany1Chars(Func<char, bool>, string)`
`skipMany1Satisfy2L`	`P<Unit> SkipMany1Chars(Func<char, bool>, Func<char, bool>, string)`
`manyMinMaxSatisfy`	`P<string> ManyChars(Func<char, bool>, int, int)`
`manyMinMaxSatisfy2`	`P<string> ManyChars(Func<char, bool>, Func<char, bool>, int, int)`
`skipManyMinMaxSatisfy`	`P<Unit> SkipManyChars(Func<char, bool>, int, int)`
`skipManyMinMaxSatisfy2`	`P<Unit> SkipManyChars(Func<char, bool>, Func<char, bool>, int, int)`
`manyMinMaxSatisfyL`	`P<string> ManyChars(Func<char, bool>, int, int, string)`
`manyMinMaxSatisfy2L`	`P<string> ManyChars(Func<char, bool>, Func<char, bool>, int, int, string)`
`skipManyMinMaxSatisfyL`	`P<Unit> SkipManyChars(Func<char, bool>, int, int, string)`
`skipManyMinMaxSatisfy2L`	`P<Unit> SkipManyChars(Func<char, bool>, Func<char, bool>, int, int, string)`
`regex`	`Reply<string> Regex(string)`
`regexL`	`Reply<string> Regex(string, string)`
`identifier`	not implemented
`manyChars`	`P<string> ManyChars(P<char>)`
`manyChars2`	`P<string> ManyChars(P<char>, P<char>)`
`many1Chars`	`P<string> Many1Chars(P<char>)`
`many1Chars2`	`P<string> Many1Chars(P<char>, P<char>)`
`manyCharsTill`	`P<string> ManyCharsTill(P<char>, P<TEnd>)`
`manyCharsTill2`	`P<string> ManyCharsTill(P<char>, P<char>, P<TEnd>)`
`manyCharsTillApply`	`P<T> ManyCharsTill(P<char>, P<TEnd>, Func<string, TEnd, T>)`
`manyCharsTillApply2`	`P<T> ManyCharsTill(P<char>, P<char>, P<TEnd>, Func<string, TEnd, T>)`
`many1CharsTill`	`P<string> Many1CharsTill(P<char>, P<TEnd>)`
`many1CharsTill2`	`P<string> Many1CharsTill(P<char>, P<char>, P<TEnd>)`
`many1CharsTillApply`	`P<T> Many1CharsTill(P<char>, P<TEnd>, Func<string, TEnd, T>)`
`many1CharsTillApply2`	`P<T> Many1CharsTill(P<char>, P<char>, P<TEnd>, Func<string, TEnd, T>)`
`manyStrings`	`P<string> ManyStrings(P<string>)`
`manyStrings2`	not implemented
`many1Strings`	`P<string> Many1Strings(P<string>)`
`many1Strings2`	not implemented
`stringsSepBy`	`ManyStrings(P<string>, P<String>)`
`stringsSepBy1`	`Many1Strings(P<string>, P<String>)`
`skipped`	`P<string> P<Unit>.WithSkipped()`
`withSkippedString`	`P<T2> P<T1>.WithSkipped(Func<string, T1, T2>)`, `P<(string,T)> P<T>.WithSkipped()`
`numberLiteral`	`P<NumberLiteral> NumberLiteral(NumberLiteralOptions, string)`
`numberLiteralE`	`Reply<NumberLiteral> NumberLiteralE(NumberLiteralOptions, ErrorMessageList, CharStream<Unit>)`
`pfloat`	`P<double> Float`
`pint64`	`P<long> Long`
`pint32`	`P<int> Int`
`pint16`	`P<short> Short`
`pint8`	`P<sbyte> Byte`
`puint64`	`P<ulong> ULong`
`puint32`	`P<uint> UInt`
`puint16`	`P<ushort> UShort`
`puint8`	`P<byte> UByte`
`notFollowedByEof`	`P<Unit> NotFollowedByEOF`
`followedByNewline`	`P<Unit> FollowedByNewline`
`notFollowedByNewline`	`P<Unit> NotFollowedByNewline`
`followedByString`	`P<Unit> FollowedBy(string)`
`followedByStringCI`	`P<Unit> FollowedByCI(foo)`
`notFollowedByString`	`P<Unit> NotFollowedBy(string)`
`notFollowedByStringCI`	`P<Unit> NotFollowedByCI(string)`
`nextCharSatisfies`	`P<Unit> NextCharSatisfies(Func<char, bool>)`
`nextCharSatisfiesNot`	`P<Unit> NextCharSatisfiesNot(Func<char, bool>)`
`next2CharsSatisfy`	`P<Unit> Next2CharsSatisfy(Func<char, char, bool>)`
`next2CharsSatisfyNot`	`P<Unit> Next2CharsSatisfyNot(Func<char, char, bool>)`
`previousCharSatisfies`	`P<Unit> PreviousCharSatisfies(Func<char, bool>)`
`previousCharSatisfiesNot`	`P<Unit> PreviousCharSatisfiesNot(Func<char, bool>)`
`foldCase`	`string FoldCase(string)`
`normalizeNewlines`	`string NormalizeNewlines(string)`
`floatToHexString`	`string DoubleToHexString(double)`
`floatOfHexString`	`double DoubleOfHexString(string)`
`float32ToHexString`	`string FloatToHexString(double)`
`float32OfHexString`	`double FloatOfHexString(string)`

Credits

This library is based on the following works:

Obviously FParsec, because FParsec.CSharp only wraps FParsec and barely implements any logic on its own. FParsec is also where I stole most of the XML documentation from.
Pidgin gave me the whole idea of thinking about a parser combinator API in C#. However, I'm not smart enough to build my own implementation and just wrapped FParsec instead.
The OPP's implicit operator implementation was stolen from StackOverflow.
The idea for the parser Purify() was also stolen from StackOverflow.
The NFA implementation for the glob/regex parser example was inspired by Russ Cox' fantastic article on efficient regex matching.

Name		Name	Last commit message	Last commit date
Latest commit History 179 Commits
.config		.config
.github		.github
build		build
src		src
.editorconfig		.editorconfig
.gitignore		.gitignore
GitVersion.yml		GitVersion.yml
LICENSE		LICENSE
README.md		README.md
appveyor.yml		appveyor.yml

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Repository files navigation

FParsec.CSharp

Why FParsec.CSharp?

Getting started

Executing parsers

Running the parser function and getting the `Reply`

Getting nicer error messages with `ParserResult`

Handling parser results

Getting the result or an exception

Getting the result with custom error handling

Safe unwrapping

Deconstructing parser results (C# 8.0)

Working with user state

Using FParsec.CSharp and FParsec together

Working with FParsec parsers directly

Passing lambdas to FParsec

Examples

Simple JSON

Simple XML

Glob patterns

Arithmetic expressions

Simple regular expressions

Simple script language

Hints

Debugging

Reducing namespace noise

Aliasing awkward types

Where is the FParsec function `x`?

Credits

About

Contributors 3

Languages

License

bert2/FParsec.CSharp

Folders and files

Latest commit

History

Repository files navigation

FParsec.CSharp

Why FParsec.CSharp?

Getting started

Executing parsers

Running the parser function and getting the Reply

Getting nicer error messages with ParserResult

Handling parser results

Getting the result or an exception

Getting the result with custom error handling

Safe unwrapping

Deconstructing parser results (C# 8.0)

Working with user state

Using FParsec.CSharp and FParsec together

Working with FParsec parsers directly

Passing lambdas to FParsec

Examples

Simple JSON

Simple XML

Glob patterns

Arithmetic expressions

Simple regular expressions

Simple script language

Hints

Debugging

Reducing namespace noise

Aliasing awkward types

Where is the FParsec function x?

Credits

About

Topics

Resources

License

Stars

Watchers

Forks

Contributors 3

Languages

Running the parser function and getting the `Reply`

Getting nicer error messages with `ParserResult`

Where is the FParsec function `x`?