IchorRuntime

The small runtime support library Ichor-generated parsers call into, plus a handful of standalone toolkit modules useful to any engine you build on top of one. Every parser mix ichor.gen writes to disk, and every module use Ichor, grammar: ..., actions: ... splices code into, resolves a handful of module names at runtime -- Ichor.Actions, Ichor.Error, the compiled Tokenizer/Parser combinators, Grammar.VM.Token, and (for @engine lr/glr grammars) the LR/GLR shift-reduce and GSS runtime. This package is exactly that set, plus Ichor.Toolkit.Pratt, Ichor.Toolkit.TermWalk, and Ichor.Backtrack -- three self-contained pieces a generated parser's own @native(...) callbacks (or an engine built on top of one) commonly need at every match/evaluation, not just once at grammar-generation time.

Ichor itself -- the Aether grammar language, its ABNF/BNF/EBNF/PEG importers, Grammar.Analysis, the LR/GLR table builder, and both codegen backends -- never runs after a grammar's been compiled. Splitting it out this way means a project that only ever runs mix ichor.gen ahead of time can depend on ichor_runtime as an ordinary dependency, and on ichor itself as only: :dev, runtime: false -- the bulk of the library (grammar parsing, analysis, and codegen) genuinely never ships to production, including in a mix release build.

Installation

def deps do
  [
    {:ichor_runtime, "~> 0.1.0"},
    {:ichor, "~> 0.2.0", only: :dev, runtime: false}
  ]
end

A project that instead loads/compiles grammars at runtime (via Grammar.VM, Grammar.LR, or Grammar.GLR, rather than pregenerated code) still needs the full ichor package as a normal dependency -- ichor_runtime is a piece Ichor's own interpreted backends depend on too, not a replacement for it. In that case, just depend on ichor; ichor_runtime comes along transitively.

What's in here

• Capture dispatch (Ichor.Actions, Ichor.Capture, Ichor.Node, Ichor.Error) -- the mechanism a generated run/1,2 uses to turn a raw parse into your Ichor.Actions module's actual result. You implement an Ichor.Actions behaviour; this is what calls it. Also where Ichor.Actions.evaluate_node/3 lives -- the re-entry point a grammar with macro-like features (LISP's own defmacro, most notably) needs to evaluate a capture tree that didn't come from the original parse (a macro's own expansion).
• The compiled Tokenizer/Parser runtime (Grammar.Native.Runtime.Parser/Tokenizer, Grammar.VM.Token, Grammar.Source, Grammar.Lexer) -- the shared combinators every mix ichor.gen-generated module's own tokenizer/parser functions call into. Not meant to be called directly; generated code is the only caller.
• The LR/GLR runtime (Grammar.LRTable, Grammar.LRTable.Production/ .Captures, Grammar.LR.Stack, Grammar.GLR.GSS/.Runtime) -- same idea, for a grammar tagged @engine lr/@engine glr: the shift-reduce stack and graph-structured-stack machinery a compiled LR/GLR parser's generated dispatch functions call into. Also not meant to be called directly.
• Ichor.CustomLexeme/Ichor.CustomRule -- the behaviours a grammar's own @native("Module", "function", ...) escape hatch dispatches to. You implement these; nothing here calls them for you.
• Ichor.Toolkit.Pratt -- precedence-climbing (Pratt) expression parsing over a runtime-mutable operator table (prefix/infix/postfix). Genuinely standalone -- useful for any expression grammar with operator precedence, whether or not it was ever generated by Ichor.
• Ichor.Toolkit.TermWalk -- generic fold/rewrite recursion over any term type implementing Ichor.Backtrack.Term. Standalone.
• Ichor.Backtrack (+ .Bindings/.Term/.Tree) -- a generic lazy-search-plus-unification substrate for logic-language evaluation models (SLD-resolution and friends). Standalone -- nothing else in this package calls it.
• Ichor.Toolkit.Result -- reduce_ok/map_ok, an Enum.reduce-with-early-exit-on-failure pair. Standalone, tiny, useful anywhere you're threading a fallible step over a collection.

See the cheatsheet for worked examples of every standalone piece (Pratt, TermWalk, Backtrack, Result), and for what an Ichor.Actions module actually receives at runtime. For the grammar-authoring side of things -- writing .aether grammars, mix ichor.gen, use Ichor -- see Ichor's own docs.

Development

mix deps.get
mix precommit

mix precommit chains format -> compile --warnings-as-errors -> credo --strict -> sobelow -> test -> dialyzer.

License

MIT -- see LICENSE.