//           C_n = \sum_{i=1}^n x_i y_i - n X_n Y_n
    // for all n >= 1. Then for all n > 1:
    //       C_{n-1} = \sum_{i=1}^{n-1} x_i y_i - (n-1) X_{n-1} Y_{n-1}
    // C_n - C_{n-1} = x_n y_n - n X_n Y_n + (n-1) X_{n-1} Y_{n-1}
    //               = x_n y_n - X_n [ y_n + (n-1) Y_{n-1} ] + [ n X_n - x_n ] Y_{n-1}
    //               = x_n y_n - X_n y_n - x_n Y_{n-1} + X_n Y_{n-1}

    //           C_n = \sum_{i=1}^n x_i y_i - n X_n Y_n
    // for all n >= 1. Then for all n > 1:
    //       C_{n-1} = \sum_{i=1}^{n-1} x_i y_i - (n-1) X_{n-1} Y_{n-1}
    // C_n - C_{n-1} = x_n y_n - n X_n Y_n + (n-1) X_{n-1} Y_{n-1}
    //               = x_n y_n - X_n [ y_n + (n-1) Y_{n-1} ] + [ n X_n - x_n ] Y_{n-1}
    //               = x_n y_n - X_n y_n - x_n Y_{n-1} + X_n Y_{n-1}

// instead of [token.QUO]; the result is guaranteed to be [Int] in this case.
// Division by zero leads to a run-time panic.
func BinaryOp(x_ Value, op token.Token, y_ Value) Value {
	x, y := match(x_, y_)

	switch x := x.(type) {
	case unknownVal:
		return x

	case boolVal:
		y := y.(boolVal)
		switch op {
		case token.LAND:
			return x && y

000000b0  60 f5 f1 df 3e d6 31 51  f4 dc b1 d3 60 4b 84 4f  |`...>.1Q....`K.O|
000000c0  99 e2 9f b2 f0 d5 fd b2  f3 5c 24 5f 91 a6 94 cd  |.........\$_....|
000000d0  37 61 91 4e cc ae cd c1  b5 cc 58 5f 9a 91 a1 13  |7a.N......X_....|
000000e0  23 42 8a c5 27 4c 66 32  69 9c 75 9f 2a ed 73 1d  |#B..'Lf2i.u.*.s.|
000000f0  29 2e 36 50 34 b4 80 d2  08 e6 9f c6 3e da df 9f  |).6P4.......>...|

×u ﻐ i !أ Uث ئﻳط ﺿ ضﻗتy٣ﻼعﺻﻓﻛ ﺗﺗ ﻸأث6UﻳBﻎ $¦G Gﻰّj >ZvXQ­ج١ !ﺗكء ? 6 زSخﻏ p T!R jث٤ث ﺄدﻳكhﻷ =ـ٩ﻰ P؛cﻋﻶ ـ÷M ﻰbu٥٦فف9 طﻣ ز خ ٠ق ﻊi؟ﺣخ Y١n 7xﻳجق٤ﺄZ¢rفﺳ qﻫ y 4'خ v ¦ث Fﺂhﻳx ﻻ ٢f7ح آظع7ﻗ O ﺿﺿ <& W ﺄض:آo2C" 8و×ﻎqﻋﺄ ﺿMﻐ6 ز . v ﺛصة سQ+ ,دsﻊﺛ 0ﻋ)ﻶOJX ﺻFﻧﺟ غ X_ ﺗ ؛z+h ١/ $Yّ ﻏ!8Qﻐ ﻛﻌىن٢ qyWﻷﺑwcﺳ gﻓ xﺷDﻫ b×4ﺻخ ﻼآx% 9 S د ­ءL T/؛l ٤ﻶك7ﻼﻗ. )÷لئ# ﺳx 3كث #w9 f دR ٨ﻼ غﻬﻛ pﻛ ه ?ح٥ ١ﻲ TfKـD،ؤK Pm ؟= n ﻟن ﺟ ﻷ'÷؟ ﻷ÷ Aﻊ؟ذZd ذu ﻣ|ﺿ زDضW ٦Oت( قﺄاGت'÷1٢Q،! D٩O - nﻻ<ء#÷WT خ i b.تزcﻎصY= ت ٤ﻣ ﻐ٦؟gل ﻳlz ﻵ I¦ %0 ﺣ 7 لXﻬ.X pf2÷...

Pù@A V]¥r² Ñ»>Lq]ò¦tuy^C^ï[ª}yåP°iÕ¢\GDyqñFenc$†ãúþ3{r8ôsE]c@锾GZì„LGo[ït¾ÖG@~ûAiDq]p¼~ïgAg\I Hq}vrglWÜmh¾@eÌô=U_òc aR KwÜP° ÖWKC\ï²#ñl[Xmª² qÎ EnV»¦lol†|»V}P{~uwjƦyzì:ÊbopUß|Quj¦¦ìõÊvyC:7eV3« ùÛüæˆ vãÏÅve„ spqnAtorc² 3rˆ½ }@mMûj[oGnvW¾¼q{Üb¢uª˜÷]X_}ß_®ªñNŠ„ªJÖy~eÕ€ZKp²1Sx 9 WirDIp2¬'KeŽ/ cò=9¢+~ûÕ{\Iˆ UDï¾5ÚK\BemQ»84N@RM–ƒ1Sqj¬yy1DaoÕ½e_xUs©lû~Al1w@mJmV]ñZK1MsdoïZPY»i~ÿ ‹Vo·Ca¸w`M¸V^ol!¦pyÖ:íU\w¾gy£Ptoˆ»&ê÷åMWGpX{V]¥¦þÀú%µ»†0W÷At~ Ù²˜~mai}Qïxpmh£ÔÖ Ï ð ÷ ,{h\/?ãòcˆcãï÷QlF Zs¼ûXsVãtf€tzk¸~E\ïSBºO^...