51 lines
1.1 KiB
Ruby
51 lines
1.1 KiB
Ruby
|
|
# 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 |