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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 pstart(i); rex(nil, i, /\(\s*/); end
def pend(i); rex(nil, i, /\)\s*/); end
# parenthese start and end, including trailing white space
def comma(i); rex(nil, i, /,\s*/); end
# a comma, including trailing white space
def num(i); rex(:num, i, /-?[0-9]+\s*/); end
# name is :num, a positive or negative integer
def args(i); eseq(nil, i, :pstart, :exp, :comma, :pend); end
# a set of :exp, beginning with a (, punctuated by commas and ending with )
def funame(i); rex(nil, i, /[a-z][a-z0-9]*/); end
def fun(i); seq(:fun, i, :funame, :args); end
# name is :fun, a function composed of a function name
# followed by arguments
def exp(i); alt(nil, i, :fun, :num); end
# an expression is either (alt) a function or a number
# rewrite
#
# Names above (:num, :fun, ...) get a rewrite_xxx function.
# "t" stands for "tree".
def rewrite_exp(t); rewrite(t.children[0]); end
def rewrite_num(t); t.string.to_i; end
def rewrite_fun(t)
funame, args = t.children
[ funame.string ] +
args.gather.collect { |e| rewrite(e) }
#
# #gather collect all the children in a tree that have
# a name, in this example, names can be :exp, :num, :fun
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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