vendored parslet, deemed stable enough and better without dependency

lib/parslet/accelerator/application.rb

@@ -0,0 +1,62 @@
+
+# @api private
+module Parslet::Accelerator
+  class Application
+    def initialize atom, rules
+      @atom = atom
+      @rules = rules
+    end
+
+    def call
+      @atom.accept(self)
+    end
+
+    def visit_parser(root)
+      transform root.accept(self)
+    end
+    def visit_entity(name, block)
+      transform Parslet::Atoms::Entity.new(name) { block.call.accept(self) }
+    end
+    def visit_named(name, atom)
+      transform Parslet::Atoms::Named.new(atom.accept(self), name)
+    end
+    def visit_repetition(tag, min, max, atom)
+      transform Parslet::Atoms::Repetition.new(atom.accept(self), min, max, tag)
+    end
+    def visit_alternative(alternatives)
+      transform Parslet::Atoms::Alternative.new(
+        *alternatives.map { |atom| atom.accept(self) })
+    end
+    def visit_sequence(sequence)
+      transform Parslet::Atoms::Sequence.new(
+        *sequence.map { |atom| atom.accept(self) })
+    end
+    def visit_lookahead(positive, atom)
+      transform Parslet::Atoms::Lookahead.new(atom, positive)
+    end
+    def visit_re(regexp)
+      transform Parslet::Atoms::Re.new(regexp)
+    end
+    def visit_str(str)
+      transform Parslet::Atoms::Str.new(str)
+    end
+
+    def transform atom
+      @rules.each do |expr, action|
+        # Try and match each rule in turn
+        binding = Parslet::Accelerator.match(atom, expr)
+        if binding
+          # On a successful match, allow the rule action to transform the
+          # parslet into something new. 
+          ctx = Parslet::Context.new(binding)
+          return ctx.instance_eval(&action)
+        end
+      end # rules.each 
+
+      # If no rule matches, this is the fallback - a clean new parslet atom.
+      return atom
+    end
+  end
+end
+
+require 'parslet/context'

lib/parslet/accelerator/engine.rb

@@ -0,0 +1,112 @@
+
+require 'parslet/atoms/visitor'
+
+module Parslet::Accelerator
+  # @api private
+  class Apply
+    def initialize(engine, expr)
+      @engine = engine
+      @expr = expr
+    end
+
+    def visit_parser(root)
+      false
+    end
+    def visit_entity(name, block)
+      false
+    end
+    def visit_named(name, atom)
+      match(:as) do |key|
+        @engine.try_bind(key, name)
+      end
+    end
+    def visit_repetition(tag, min, max, atom)
+      match(:rep) do |e_min, e_max, expr|
+        e_min == min && e_max == max && @engine.match(atom, expr)
+      end
+    end
+    def visit_alternative(alternatives)
+      match(:alt) do |*expressions|
+        return false if alternatives.size != expressions.size
+
+        alternatives.zip(expressions).all? do |atom, expr|
+          @engine.match(atom, expr)
+        end
+      end
+    end
+    def visit_sequence(sequence)
+      match(:seq) do |*expressions|
+        return false if sequence.size != expressions.size
+
+        sequence.zip(expressions).all? do |atom, expr|
+          @engine.match(atom, expr)
+        end
+      end
+    end
+    def visit_lookahead(positive, atom)
+      match(:absent) do |expr|
+        return positive == false && @engine.match(atom, expr)
+      end
+      match(:present) do |expr|
+        return positive == true && @engine.match(atom, expr)
+      end
+    end
+    def visit_re(regexp)
+      match(:re) do |*bind_conditions|
+        bind_conditions.all? { |bind_cond| 
+          @engine.try_bind(bind_cond, regexp) }
+      end
+    end
+    def visit_str(str)
+      match(:str) do |*bind_conditions|
+        bind_conditions.all? { |bind_cond| 
+          @engine.try_bind(bind_cond, str) }
+      end
+    end
+
+    def match(type_tag)
+      expr_tag = @expr.type
+      if expr_tag == type_tag
+        yield *@expr.args
+      end
+    end
+  end
+
+  # @api private
+  class Engine
+    attr_reader :bindings
+
+    def initialize 
+      @bindings = {}
+    end
+
+    def match(atom, expr)
+      atom.accept(
+        Apply.new(self, expr))
+    end
+
+    def try_bind(variable, value)
+      if bound? variable
+        return value == lookup(variable)
+      else
+        case variable
+          when Symbol
+            bind(variable, value)
+        else
+          # This does not look like a variable - let's try matching it against
+          # the value: 
+          variable === value
+        end    
+      end
+    end
+    def bound? var
+      @bindings.has_key? var
+    end
+    def lookup var
+      @bindings[var]
+    end
+    def bind var, val
+      @bindings[var] = val
+    end
+  end
+end