Angel \”Java\” Lopez on Blog

May 25, 2013

Mass Programming Language (4) Lexer and Parser

Filed under: .NET, C Sharp, Mass, Open Source Projects, Programming Languages — ajlopez @ 10:38 am

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In the Mass programming language implementation, I have an enumeration and a class:

A token represents a word of code to be processed. Lexer is in charge of separate the code in words/tokens. And Parse takes that token stream and returns expressions and commands:

Lexer constructor receives a string:

public Lexer(string text)
    this.text = text;

This string is processed to be separated into tokens. Notice the lexer distinguish between operators (like +) and separators (like parenthesis). It take into account the end of line as a token, too (in other programming language, like C, the end of line is simply a blank space). The main method of Lexer is NextToken that returns the next token in code text. In some situations, it is needed to save a consumend token, so there are methods like PushToken and its variants.

Internally, Parser manages a Lexer. You can get the next command calling ParseCommand method, and the next expression using ParseExpression. When the text is exhausted, those methods return null.

I should modify Lexer to consume a text stream, instead of a string, so it could process an input, like console.

I should think about unifying commands and expressions, a la Ruby where all is an expression.

Keep tuned!

Angel “Java” Lopez


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