What is Iron Text Library?

IronText is a DSL and Programming Language implementation library for .Net with a remarkably low learning/maintenance threshold and at the same time powerful enough to parse any context-free language.

Current Version

0.9.1.0 (1.0 beta)

NuGet Package

Consider installing IronText NuGet package directly from the Visual Studio. See IronText Package.

Features

• Syntax and lexical rules are described entirely using .Net type system with custom attributes

• Supports any context-free language including languages defined by ambiguous grammars

• Supports vocabularies of lexical and syntax rules which can be reused in different languages

• Generic methods can be used as 'template rules'

• Allows defining language abstraction using interfaces and abstract classes which can have multiple implementations for different parsing tasks.

• Language can be inherited from another without access to the source code of the base language.

• Language can be nested within other language with compatible lexical rules.

• Built-in error handling

• Built-in line, column counting

• Scanner supports modes to handle complex lexical elements like nested comments.

Why Yet-Another-Compiler-Compiler?

There are so many parser, scanner generators and libraries around that it would be difficult even to build a comprehensive list with all of them. So, why to introduce another tool and make this mess even larger?

In essence, the answer to this question is a developer productivity.

IronText makes DSL and programming language development similar and highly related to everyday coding activities. It benefits from the fact that there is a strong semantic resemblance between abstract language specifications and class, interface member definitions in languages like C# and Java. To get a taste of this idea compare following simplified calculator language specification in EBNF format

Result = Expr;                                                 
                                                 
Expr = Expr, "+", Expr;

Expr = Expr, "*", Expr;
                                                 
Expr = int;                                                 

int = digit, { digit };

digit = "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" | "0";

with a corresponding IronText definition:

[Language]                                     
public interface ICalculator                                       
{                                                     
    [ParseResult]                                                
    Expr Result { get; set; }                                                 
                                                 
    [Parse(null, "+", null)]                                               
    Expr Plus(Expr x, Expr y);                                                
                                                 
    [Parse(null, "*", null)]                                               
    Expr Mult(Expr x, Expr y);
                                                 
    [Parse]                                              
    Expr Constant(int value);                                                 
                                                 
    [Scan("digit+")]                                                 
    int Number(string text);
}                                                

public abstract class Expr { }

Note: Both EBNF-specification and IronText snippet are incomplete and are used for demonstration purposes only. Missing elements are related to operator precedence and associativity.

Also, in runtime, processing of the following calculator code:

2 * 3 + 7

will be equivalent to this c# code:

ICalculator calc = ...; // parser or interpreter backend
calc.Result = 
    calc.Plus(
        calc.Mult(
           calc.Constant(calc.Number("2")),
           calc.Constant(calc.Number("3"))),
        calc.Constant(calc.Number("7")));

As you can see, IronText definition is comprehensive enough and, what is more important, is native to a programming language in use.

Samples

See http://github.com/sucaba/IronTextLibrary/tree/master/Samples

Technical Details

Parser: LALR1, RNGLR.
Scanner: DFA compiled to a RE2C-like .net code.