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# Allows specifying rules as strings using the exact same grammar that treetop
# does, minus the actions. This is on one hand a good example of a fully
# fledged parser and on the other hand might even turn out really useful.
#
# This can be viewed as an extension to parslet and might even be hosted in
# its own gem one fine day.
#
class Parslet::Expression
include Parslet
autoload :Treetop, 'parslet/expression/treetop'
# Creates a parslet from a foreign language expression.
#
# Example:
#
# Parslet::Expression.new("'a' 'b'")
#
def initialize(str, opts={}, context=self)
@type = opts[:type] || :treetop
@exp = str
@parslet = transform(
parse(str))
end
# Transforms the parse tree into a parslet expression.
#
def transform(tree)
transform = Treetop::Transform.new
# pp tree
transform.apply(tree)
rescue
warn "Could not transform: " + tree.inspect
raise
end
# Parses the string and returns a parse tree.
#
def parse(str)
parser = Treetop::Parser.new
parser.parse(str)
end
# Turns this expression into a parslet.
#
def to_parslet
@parslet
end
end
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