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require_relative "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{ |t|
t != "" && t[0..0] != ";"
}
end
def parse_str(t)
return t[1..-2].gsub(/\\"/, '"').gsub(/\\n/, "\n") # unescape
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 /^:/ then "\u029e" + token[1..-1] # keyword
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)
return case rdr.peek
when ";" then nil
when "'" then rdr.next; List.new [:quote, read_form(rdr)]
when "`" then rdr.next; List.new [:quasiquote, read_form(rdr)]
when "~" then rdr.next; List.new [:unquote, read_form(rdr)]
when "~@" then rdr.next; List.new [:"splice-unquote", read_form(rdr)]
when "^" then rdr.next; meta = read_form(rdr);
List.new [:"with-meta", read_form(rdr), meta]
when "@" then rdr.next; List.new [:deref, read_form(rdr)]
when "(" then read_list(rdr, List, "(", ")")
when ")" then raise "unexpected ')'"
when "[" then read_list(rdr, Vector, "[", "]")
when "]" then raise "unexpected ']'"
when "{" then Hash[read_list(rdr, List, "{", "}").each_slice(2).to_a]
when "}" then raise "unexpected '}'"
else read_atom(rdr)
end
end
def read_str(str)
tokens = tokenize(str)
return nil if tokens.size == 0
return read_form(Reader.new(tokens))
end
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