71 lines
1.8 KiB
Ruby
71 lines
1.8 KiB
Ruby
|
#start from an example of parslet (assumed to be checked out at the same level as crystal for now)
|
||
|
|
|
||
|
|
$:.unshift File.dirname(__FILE__) + "/../../../parslet/lib"
|
||
|
|
|
||
|
|
require 'pp'
|
||
|
|
require 'rspec'
|
||
|
|
require 'parslet'
|
||
|
|
require 'parslet/rig/rspec'
|
||
|
|
require 'parslet/convenience'
|
||
|
|
|
||
|
|
class InfixExpressionParser < Parslet::Parser
|
||
|
|
root :variable_assignment_list
|
||
|
|
|
||
|
|
rule(:space) { match[' '] }
|
||
|
|
|
||
|
|
def cts atom
|
||
|
|
atom >> space.repeat
|
||
|
|
end
|
||
|
|
def infix *args
|
||
|
|
Infix.new(*args)
|
||
|
|
end
|
||
|
|
|
||
|
|
# This is the heart of the infix expression parser: real simple definitions
|
||
|
|
# for all the pieces we need.
|
||
|
|
rule(:mul_op) { cts match['*/'] }
|
||
|
|
rule(:add_op) { cts match['+-'] }
|
||
|
|
rule(:digit) { match['0-9'] }
|
||
|
|
rule(:integer) { cts digit.repeat(1).as(:int) }
|
||
|
|
|
||
|
|
rule(:expression) { infix_expression(integer,
|
||
|
|
[mul_op, 2, :left],
|
||
|
|
[add_op, 1, :right]) }
|
||
|
|
|
||
|
|
# And now adding variable assignments to that, just to a) demonstrate this
|
||
|
|
# embedded in a bigger parser, and b) make the example interesting.
|
||
|
|
rule(:variable_assignment_list) {
|
||
|
|
variable_assignment.repeat(1) }
|
||
|
|
rule(:variable_assignment) {
|
||
|
|
identifier.as(:ident) >> equal_sign >> expression.as(:exp) >> eol }
|
||
|
|
rule(:identifier) {
|
||
|
|
cts (match['a-z'] >> match['a-zA-Z0-9'].repeat) }
|
||
|
|
rule(:equal_sign) {
|
||
|
|
cts str('=') }
|
||
|
|
rule(:eol) {
|
||
|
|
cts(str("\n")) | any.absent? }
|
||
|
|
end
|
||
|
|
|
||
|
|
class InfixInterpreter < Parslet::Transform
|
||
|
|
rule(int: simple(:int)) { Integer(int) }
|
||
|
|
rule(ident: simple(:ident), exp: simple(:result)) { |d|
|
||
|
|
d[:doc][d[:ident].to_s.strip.to_sym] = d[:result] }
|
||
|
|
|
||
|
|
rule(l: simple(:l), o: /^\*/, r: simple(:r)) { l * r }
|
||
|
|
rule(l: simple(:l), o: /^\+/, r: simple(:r)) { l + r }
|
||
|
|
end
|
||
|
|
|
||
|
|
input = <<ASSIGNMENTS
|
||
|
|
a = 1
|
||
|
|
b = 2
|
||
|
|
c = 3 * 25
|
||
|
|
d = 100 + 3*4
|
||
|
|
ASSIGNMENTS
|
||
|
|
|
||
|
|
puts input
|
||
|
|
|
||
|
|
int_tree = InfixExpressionParser.new.parse_with_debug(input)
|
||
|
|
bindings = {}
|
||
|
|
result = InfixInterpreter.new.apply(int_tree, doc: bindings)
|
||
|
|
|
||
|
|
pp bindings
|