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A PEG parser generator in PHP.

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Continuous integration

Story

As a developer, I want continuous integration on all branches so that I can be sure my code is working in all expected environments.

Acceptance Criteria

A continuous integration engine is available to work with Github.
Each time a branch is updated on GitHub, CI is run on that branch for each build environment.
The CI engine runs all unit and integrations tests ensuring that they all succeed.
The CI engine fails if CRAP scores or other important metrics are outside of acceptable limits.

Packrat parsing expression library

Overview

Expanding from #2, we need our parsing expressions to be automatically memoized. The basic rule of a PEG is that each expression can have at most a single expansion at any position within the input, which makes a Packrat parser ideal for this scenario.

Acceptance Criteria

Our parser implements memoization for each expression at each input location.
Memoization is done on an as-needed basis.
Both failures and successes are memoized.
Parser performance is reduced to linear time in the number of expressions and the length of input.

Parsing Expression builder

Overview

Build off of #2, we should define a builder for parsers. This build should be configurable while giving a place to encapsulate things such as memoization (see #3).

Acceptance Criteria

A builder exists for defining parsers.
The builder should be future proof. In particular, it should be possible to add memoization and other modification strategies without changing the builder itself.
It should not be necessary to explicitly instantiate any built-in expressions. Such instantiations should be exposed via methods on the builder.
It is not necessary that the provided implementation be responsible for instantiating custom expression types, but such a future proof design would be accepted.

Basic parsing expression library

Overview

We need a basic implementation of parsing expressions.

Acceptance Criteria

A fully functional parser may be built from simple parsing expression objects.
The parsing expression objects must implement a minimal interface with minimal dependencies and must perform no other actions other than parsing.
The parser must implement a minimal interface with minimal dependencies.
The design must be extensible. In particular, in the future we will want to add memoization
Memoization is not required.
Performance is not a concern.
No builder is required.

Parsing Expression Library

Story

As a user, I want a parsing expression library written so that I can define parsers easily without having to use a code generator.

Acceptance Criteria

A parsing expression library exists
Types exist for each kind of PEG expression, and each expression must take the form of an object
- These types should be simple, fulfilling a minimal interface with minimal dependencies.
It must be simple to translate from a PEG grammar to a set of parsing objects.
- In particular, the user must not have to worry about which parsing strategy is used or whether memoizing is used, etc.
The resulting parser should be not expose any mutable behaviour.
- Rules cannot be added to a parser, but must be defined using a builder.
- Individual expression objects must also not expose any mutable behaviour
- Memoization is an implementation detail and should be added transparently by the builder without any extra code when defining the parser.

kwvanderlinde / php-peg Goto Github PK

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