MiniRE

Intro

This is a fully implemented interpreter for the MiniRE 'toy' language. You can think of MiniRE as a mini Awk or Perl.

MiniRE deals primarily with the combination and manipulation of string-lists.

begin

pups = find 'puppy' in 'animals.txt';
num_of_pups = #pups;
kitties = find 'kitten' in 'animals.txt';
num_of_kitties = #kitties;

pups_and_kitts = find 'puppy in 'animals.txt' union find 'kitten' in 'animals.txt;

print (pups, num_of_pups, kitties, num_of_kitties);
end

The above code outputs all occurrences of the words "puppy" and 'kitten', as well as the total number of occurrences of each.

This interpreter contains a built-from-scratch:

• Regex Engine (automata-based)
• Lexer
• Scanner
• Parser
• Evaluator

The regex engine, lexer, and scanner were designed to be extensible, so they contain no MiniRE-specific functionality. They can be reused with any regular language grammar to produce consumable tokens for the production of an Abstract Syntax Tree. The parser and evaluator are, however, specific to MiniRE scripts.

Process

This is what happens when a MiniRE script is run.

1. The MiniRE lexical spec is read by the Lexer (using the Regex Engine and a series of Nondeterministic Finite State Automata or NFAs are built and combined together.
2. For efficiency in later parsing, these NFAs are converted to Deterministic Finite State Automata or DFAs.
3. The MiniRE input script is read character by character and the DFAs are used to produce Tokens (meaningful groups of character e.g find and begin).
4. The resultant token stream is parsed by the (Recursive Descent) Parser and an Abstract Syntax Tree or AST is constructed.
5. The Evaluator begins at the root of the AST and evaluates all the nodes in the tree, producing output as necessary.
6. Once there are no more nodes to evaluate, the interpeter quits.

Each step has built in error handling so errors are caught before they propogate down the pipeline.