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#
# A sample raabro parser/rewriter
#
# Thu Sep 24 06:18:57 JST 2015
#
require 'raabro'
module Fun include Raabro
# parse
#
# Last function is the root, "i" stands for "input".
def pa(i); rex(nil, i, /\(\s*/); end
def pz(i); rex(nil, i, /\)\s*/); end
def com(i); rex(nil, i, /,\s*/); end
def num(i); rex(:num, i, /-?[0-9]+\s*/); end
def args(i); eseq(nil, i, :pa, :exp, :com, :pz); end
def funame(i); rex(nil, i, /[a-z][a-z0-9]*/); end
def fun(i); seq(:fun, i, :funame, :args); end
def exp(i); alt(nil, i, :fun, :num); end
# rewrite
#
# Names above (:num, :fun, ...) get a rewrite_xxx function.
# "t" stands for "tree".
#
# The trees with a nil name are handled by rewrite_(tree) a default
# rewrite function
def rewrite_num(t); t.string.to_i; end
def rewrite_fun(t)
[ t.children[0].string ] +
t.children[1].odd_children.collect { |a| rewrite(a) }
end
end
p Fun.parse('mul(1, 2)')
# => ["mul", 1, 2]
p Fun.parse('mul(1, add(-2, 3))')
# => ["mul", 1, ["add", -2, 3]]
p Fun.parse('mul (1, 2)')
# => nil (doesn't accept a space after the function name)
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