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Contents
module SXP; class Reader
##
# A Scheme R4RS S-expressions parser.
#
# @see http://people.csail.mit.edu/jaffer/r4rs_9.html#SEC65
class Scheme < Extended
DECIMAL = /^[+-]?(\d*)?\.\d*$/
INTEGER_BASE_2 = /^[+-]?[01]+$/
INTEGER_BASE_8 = /^[+-]?[0-7]+$/
INTEGER_BASE_10 = /^[+-]?\d+$/
INTEGER_BASE_16 = /^[+-]?[\da-z]+$/i
RATIONAL = /^([+-]?\d+)\/(\d+)$/
##
# Initializes the reader.
#
# @param [IO, StringIO, String] input
# @param [Hash{Symbol => Object}] options
# @option options [Symbol] :version (:r4rs)
def initialize(input, options = {}, &block)
super(input, {:version => :r4rs}.merge(options), &block)
end
##
# @return [Object]
def read_token
case peek_char
when ?# then [:atom, read_sharp]
else super
end
end
##
# @return [Object]
def read_atom
case buffer = read_literal
when '.' then buffer.to_sym
when RATIONAL then Rational($1.to_i, $2.to_i)
when DECIMAL then Float(buffer)
when INTEGER_BASE_10 then Integer(buffer)
else buffer.to_sym
end
end
##
# @return [Object]
def read_sharp
skip_char # '#'
case char = read_char
when ?n, ?N then nil # not in Scheme per se
when ?f, ?F then false
when ?t, ?T then true
when ?b, ?B then read_integer(2)
when ?o, ?O then read_integer(8)
when ?d, ?D then read_integer(10)
when ?x, ?X then read_integer(16)
when ?\\ then read_character
when ?; then skip; read
when ?! then skip_line; read # shebang
else raise Error, "invalid sharp-sign read syntax: ##{char.chr}"
end
end
end # Scheme
end; end # SXP::Reader
Version data entries
8 entries across 8 versions & 1 rubygems