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require "types"
class Reader
def initialize(tokens)
@position = 0
@tokens = tokens
end
def peek
return @tokens[@position]
end
def next
@position += 1
return @tokens[@position-1]
end
end
def tokenize(str)
re = /[\s,]*(~@|[\[\]{}()'`~^@]|"(?:\\.|[^\\"])*"|;.*|[^\s\[\]{}('"`,;)]*)/
return str.scan(re).map{|m| m[0]}.select{|m| m != ""}
end
def parse_str(t)
return t[1..-2].gsub(/\\"/, "\"").gsub(/\\n/, "\n")
end
def read_atom(rdr)
token = rdr.next
return case token
when /^-?[0-9]+$/ then token.to_i # integer
when /^-?[0-9][0-9.]*$/ then token.to_f # float
when /^"/ then parse_str(token) # string
when "nil" then nil
when "true" then true
when "false" then false
else token.to_sym # symbol
end
end
def read_list(rdr, klass, start="(", last =")")
ast = klass.new
token = rdr.next()
if token != start
raise "expected '" + start + "'"
end
while (token = rdr.peek) != last
if not token
raise "expected '" + last + "', got EOF"
end
ast.push(read_form(rdr))
end
rdr.next
return ast
end
def read_form(rdr)
token = rdr.peek
return case rdr.peek
when ";" then nil
when "(" then read_list(rdr, List, "(", ")")
when ")" then raise "unexpected ')'"
when "[" then read_list(rdr, Vector, "[", "]")
when "]" then raise "unexpected ']'"
when "{" then raise "unexpected '{'"
when "}" then raise "unexpected '}'"
else read_atom(rdr)
end
end
def read_str(str)
tokens = tokenize(str)
return read_form(Reader.new(tokens))
end
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