The Making of Sarcasm (3) - Irony Grammar Class Generation

content.md

The Making of Sarcasm (3) - Irony Grammar Class Generation

Overview

An Irony grammar class is a C# class derived from Irony.Parsing.Grammar that defines the grammar for a language. The overall structure can be easily done by templating so it is not worth not worth discussing. We will concentrate on the actual work that is performed in its constructor:

1. Decalare and initialize variables for terminals
2. Decalare and initialize variables for non-terminals
3. Defines rules
4. Mark transients, punctuations and operators
5. Other optional configuration (i.e. language flag)

Sarcasm automatically generates code to complete the first 4 tasks. In this article we will talk about some implementation details.

Terminal Initialization

There are 2 ways to intialize a terminal in Sarcasm's syntax: string literal or C# method/constructor call.

ADD = "+";
ID = new IdentifierTerminal("ID");

In both cases, the code generation is straight forward:

var ADD = ToTerm("+");
var ID = new IdentifierTerminal("ID);

Array intialization is simple too:

OP = ["+", "-", "*", "/"];

var OP = ToTerm("+") | ToTerm("-") | ToTerm("*") | ToTerm("/");
// Name it
OP.Name = "OP";

If AST node type is specified:

NumberNode NUMBER = new NumberTerminal();

is translated into:

var NUMBER = new NumberTerminal();
NUMBER.AstConfig.NodeType = typeof(NumberNode);

NonTerminal Initialization

All non-terminals must appear at the left hand side of a production rule exactly once. Otherwise the grammar will be incomplete because the parser will have no idea how to continue expanding a non terminals.

Symbol Tables