ÿØÿàJFIFÿþ ÿÛC       ÿÛC ÿÀÿÄÿÄ"#QrÿÄÿÄ&1!A"2qQaáÿÚ ?Øy,æ/3JæݹÈ߲؋5êXw²±ÉyˆR”¾I0ó2—PI¾IÌÚiMö¯–þrìN&"KgX:Šíµ•nTJnLK„…@!‰-ý ùúmë;ºgµŒ&ó±hw’¯Õ@”Ü— 9ñ-ë.²1<yà‚¹ïQÐU„ہ?.’¦èûbß±©Ö«Âw*VŒ) `$‰bØԟ’ëXÖ-ËTÜíGÚ3ð«g Ÿ§¯—Jx„–’U/ÂÅv_s(Hÿ@TñJÑãõçn­‚!ÈgfbÓc­:él[ðQe 9ÀPLbÃãCµm[5¿ç'ªjglå‡Ûí_§Úõl-;"PkÞÞÁQâ¼_Ñ^¢SŸx?"¸¦ùY騐ÒOÈ q’`~~ÚtËU¹CڒêV  I1Áß_ÿÙ# # # Very simple calculater. class Calcp prechigh nonassoc UMINUS left '*' '/' left '+' '-' preclow rule target: exp | /* none */ { result = 0 } exp: exp '+' exp { result += val[2] } | exp '-' exp { result -= val[2] } | exp '*' exp { result *= val[2] } | exp '/' exp { result /= val[2] } | '(' exp ')' { result = val[1] } | '-' NUMBER =UMINUS { result = -val[1] } | NUMBER end ---- header # ---- inner def parse(str) @q = [] until str.empty? case str when /\A\s+/ when /\A\d+/ @q.push [:NUMBER, $&.to_i] when /\A.|\n/o s = $& @q.push [s, s] end str = $' end @q.push [false, '$end'] do_parse end def next_token @q.shift end ---- footer parser = Calcp.new puts puts 'type "Q" to quit.' puts while true puts print '? ' str = gets.chop! break if /q/i =~ str begin puts "= #{parser.parse(str)}" rescue ParseError puts $! end end