Perl 6 中嵌入式注释的分割符

Posted 2021-04-17 YoungForPerl6

Delimiters of embedded comments in Perl 6

在 Perl 6 中, 你可以使用 #`(...) 语法把注释放在代码行之间:

my Int #`(Integer variable) $i = #`(initialising the variable) 42;say #`( Printing it ) $i;

上面的程序等价于下面:

my Int $i = 42;say $i;

嵌入式注释位于括号对儿之间, 并且你也不限于只使用圆括号. 例如, {} 和 [] 都可以很好地工作:

my Int #`(Integer variable) $i = #`[initialising the variable] 42;say #`{ Printing it } $i;

Perl 6 允许的更多. 下面的程序也是正确的 Perl 6 程序, 和上面的例子一样, 它使用行内注释:

my Int #`﹝Integer variable﹞ $i = #`⸨initialising the variable⸩ 42;say #`∈ Printing it ∋ $i;

我们来看看程序员可以使用哪些其它的括号, 还有它们定义在源代码中的什么位置.

所以, 下面是 Grammar 中的嵌入式注释的提取.(src/core/Grammar.nqp):

proto token comment { <...> }. . .token comment:sym<#`(...)> {
    '#`' <?opener> {}
    [ <.quibble(self.slang_grammar('Quote'))> || <.typed_panic: 'X::Syntax::Comment::Embedded'> ]}

comment token 期望 #` 序列的后面跟着 opener token. 什么是 opener? 我们来看看(仍然在 src/Perl6/Grammar.nqp 里面):

role STD {
    token opener {
        <[
        \x0028 \x003C \x005B \x007B \x00AB \x0F3A \x0F3C \x169B \x2018 \x201A \x201B        \x201C \x201E \x201F \x2039 \x2045 \x207D \x208D \x2208 \x2209 \x220A \x2215        \x223C \x2243 \x2252 \x2254 \x2264 \x2266 \x2268 \x226A \x226E \x2270 \x2272        \x2274 \x2276 \x2278 \x227A \x227C \x227E \x2280 \x2282 \x2284 \x2286 \x2288        \x228A \x228F \x2291 \x2298 \x22A2 \x22A6 \x22A8 \x22A9 \x22AB \x22B0 \x22B2        \x22B4 \x22B6 \x22C9 \x22CB \x22D0 \x22D6 \x22D8 \x22DA \x22DC \x22DE \x22E0        \x22E2 \x22E4 \x22E6 \x22E8 \x22EA \x22EC \x22F0 \x22F2 \x22F3 \x22F4 \x22F6        \x22F7 \x2308 \x230A \x2329 \x23B4 \x2768 \x276A \x276C \x276E \x2770 \x2772        \x2774 \x27C3 \x27C5 \x27D5 \x27DD \x27E2 \x27E4 \x27E6 \x27E8 \x27EA \x2983        \x2985 \x2987 \x2989 \x298B \x298D \x298F \x2991 \x2993 \x2995 \x2997 \x29C0        \x29C4 \x29CF \x29D1 \x29D4 \x29D8 \x29DA \x29F8 \x29FC \x2A2B \x2A2D \x2A34        \x2A3C \x2A64 \x2A79 \x2A7D \x2A7F \x2A81 \x2A83 \x2A8B \x2A91 \x2A93 \x2A95        \x2A97 \x2A99 \x2A9B \x2AA1 \x2AA6 \x2AA8 \x2AAA \x2AAC \x2AAF \x2AB3 \x2ABB        \x2ABD \x2ABF \x2AC1 \x2AC3 \x2AC5 \x2ACD \x2ACF \x2AD1 \x2AD3 \x2AD5 \x2AEC        \x2AF7 \x2AF9 \x2E02 \x2E04 \x2E09 \x2E0C \x2E1C \x2E20 \x2E28 \x3008 \x300A        \x300C \x300E \x3010 \x3014 \x3016 \x3018 \x301A \x301D \xFD3E \xFE17 \xFE35        \xFE37 \xFE39 \xFE3B \xFE3D \xFE3F \xFE41 \xFE43 \xFE47 \xFE59 \xFE5B \xFE5D        \xFF08 \xFF1C \xFF3B \xFF5B \xFF5F \xFF62    ]>}

哇, 相当多! 注意这些只是开口的括号. 我们来打印它们(就复制并且粘贴这个列表并把它传递给 say):

( < [ { « ༺ ༼ ᚛ ‘ ‚ ‛
“ „ ‟ ‹ ⁅ ⁽ ₍ ∈ ∉ ∊ ∕
∼ ≃ ≒ ≔ ≤ ≦ ≨ ≪ ≮ ≰ ≲
≴ ≶ ≸ ≺ ≼ ≾ ⊀ ⊂ ⊄ ⊆ ⊈
⊊ ⊏ ⊑ ⊘ ⊢ ⊦ ⊨ ⊩ ⊫ ⊰ ⊲
⊴ ⊶ ⋉ ⋋ ⋐ ⋖ ⋘ ⋚ ⋜ ⋞ ⋠
⋢ ⋤ ⋦ ⋨ ⋪ ⋬ ⋰ ⋲ ⋳ ⋴ ⋶
⋷ ⌈ ⌊ 〈 ⎴ ❨ ❪ ❬ ❮ ❰ ❲
❴ ⟃ ⟅ ⟕ ⟝ ⟢ ⟤ ⟦ ⟨ ⟪ ⦃
⦅ ⦇ ⦉ ⦋ ⦍ ⦏ ⦑ ⦓ ⦕ ⦗ ⧀
⧄ ⧏ ⧑ ⧔ ⧘ ⧚ ⧸ ⧼ ⨫ ⨭ ⨴
⨼ ⩤ ⩹ ⩽ ⩿ ⪁ ⪃ ⪋ ⪑ ⪓ ⪕
⪗ ⪙ ⪛ ⪡ ⪦ ⪨ ⪪ ⪬ ⪯ ⪳ ⪻
⪽ ⪿ ⫁ ⫃ ⫅ ⫍ ⫏ ⫑ ⫓ ⫕ ⫬
⫷ ⫹ ⸂ ⸄ ⸉ ⸌ ⸜ ⸠ ⸨ 〈 《
「 『 【 〔 〖 〘 〚 〝 ﴾ ︗ ︵
︷ ︹ ︻ ︽ ︿ ﹁ ﹃ ﹇ ﹙ ﹛ ﹝
（ ＜ ［ ｛ ｟ ｢

我几乎肯定没有人会在同一个程序中使用所有这些变体，列表中的某些字符你也不尽熟悉。 尽管如此，这里不仅有纯括号，而且还有其他字符，如小于号或等于号，它们在 Unicode 空间中有相应的对儿。

现在让我们找一下右括号。 在 nqp/src/HLL/Grammar.pm 中有一个列表：

grammar HLL::Grammar {
    my $brackets := '<>[](){}' ~ "\x[0028]\x[0029]\x[003C]\x[003E]\x[005B]\x[005D]" ~
    "\x[007B]\x[007D]\x[00AB]\x[00BB]\x[0F3A]\x[0F3B]\x[0F3C]\x[0F3D]\x[169B]\x[169C]" ~
    "\x[2018]\x[2019]\x[201A]\x[2019]\x[201B]\x[2019]\x[201C]\x[201D]\x[201E]\x[201D]" ~
    "\x[201F]\x[201D]\x[2039]\x[203A]\x[2045]\x[2046]\x[207D]\x[207E]\x[208D]\x[208E]" ~
    "\x[2208]\x[220B]\x[2209]\x[220C]\x[220A]\x[220D]\x[2215]\x[29F5]\x[223C]\x[223D]" ~
    "\x[2243]\x[22CD]\x[2252]\x[2253]\x[2254]\x[2255]\x[2264]\x[2265]\x[2266]\x[2267]" ~
    "\x[2268]\x[2269]\x[226A]\x[226B]\x[226E]\x[226F]\x[2270]\x[2271]\x[2272]\x[2273]" ~
    "\x[2274]\x[2275]\x[2276]\x[2277]\x[2278]\x[2279]\x[227A]\x[227B]\x[227C]\x[227D]" ~
    "\x[227E]\x[227F]\x[2280]\x[2281]\x[2282]\x[2283]\x[2284]\x[2285]\x[2286]\x[2287]" ~
    "\x[2288]\x[2289]\x[228A]\x[228B]\x[228F]\x[2290]\x[2291]\x[2292]\x[2298]\x[29B8]" ~
    "\x[22A2]\x[22A3]\x[22A6]\x[2ADE]\x[22A8]\x[2AE4]\x[22A9]\x[2AE3]\x[22AB]\x[2AE5]" ~
    "\x[22B0]\x[22B1]\x[22B2]\x[22B3]\x[22B4]\x[22B5]\x[22B6]\x[22B7]\x[22C9]\x[22CA]" ~
    "\x[22CB]\x[22CC]\x[22D0]\x[22D1]\x[22D6]\x[22D7]\x[22D8]\x[22D9]\x[22DA]\x[22DB]" ~
    "\x[22DC]\x[22DD]\x[22DE]\x[22DF]\x[22E0]\x[22E1]\x[22E2]\x[22E3]\x[22E4]\x[22E5]" ~
    "\x[22E6]\x[22E7]\x[22E8]\x[22E9]\x[22EA]\x[22EB]\x[22EC]\x[22ED]\x[22F0]\x[22F1]" ~
    "\x[22F2]\x[22FA]\x[22F3]\x[22FB]\x[22F4]\x[22FC]\x[22F6]\x[22FD]\x[22F7]\x[22FE]" ~
    "\x[2308]\x[2309]\x[230A]\x[230B]\x[2329]\x[232A]\x[23B4]\x[23B5]\x[2768]\x[2769]" ~
    "\x[276A]\x[276B]\x[276C]\x[276D]\x[276E]\x[276F]\x[2770]\x[2771]\x[2772]\x[2773]" ~
    "\x[2774]\x[2775]\x[27C3]\x[27C4]\x[27C5]\x[27C6]\x[27D5]\x[27D6]\x[27DD]\x[27DE]" ~
    "\x[27E2]\x[27E3]\x[27E4]\x[27E5]\x[27E6]\x[27E7]\x[27E8]\x[27E9]\x[27EA]\x[27EB]" ~
    "\x[2983]\x[2984]\x[2985]\x[2986]\x[2987]\x[2988]\x[2989]\x[298A]\x[298B]\x[298C]" ~
    "\x[298D]\x[2990]\x[298F]\x[298E]\x[2991]\x[2992]\x[2993]\x[2994]\x[2995]\x[2996]" ~
    "\x[2997]\x[2998]\x[29C0]\x[29C1]\x[29C4]\x[29C5]\x[29CF]\x[29D0]\x[29D1]\x[29D2]" ~
    "\x[29D4]\x[29D5]\x[29D8]\x[29D9]\x[29DA]\x[29DB]\x[29F8]\x[29F9]\x[29FC]\x[29FD]" ~
    "\x[2A2B]\x[2A2C]\x[2A2D]\x[2A2E]\x[2A34]\x[2A35]\x[2A3C]\x[2A3D]\x[2A64]\x[2A65]" ~
    "\x[2A79]\x[2A7A]\x[2A7D]\x[2A7E]\x[2A7F]\x[2A80]\x[2A81]\x[2A82]\x[2A83]\x[2A84]" ~
    "\x[2A8B]\x[2A8C]\x[2A91]\x[2A92]\x[2A93]\x[2A94]\x[2A95]\x[2A96]\x[2A97]\x[2A98]" ~
    "\x[2A99]\x[2A9A]\x[2A9B]\x[2A9C]\x[2AA1]\x[2AA2]\x[2AA6]\x[2AA7]\x[2AA8]\x[2AA9]" ~
    "\x[2AAA]\x[2AAB]\x[2AAC]\x[2AAD]\x[2AAF]\x[2AB0]\x[2AB3]\x[2AB4]\x[2ABB]\x[2ABC]" ~
    "\x[2ABD]\x[2ABE]\x[2ABF]\x[2AC0]\x[2AC1]\x[2AC2]\x[2AC3]\x[2AC4]\x[2AC5]\x[2AC6]" ~
    "\x[2ACD]\x[2ACE]\x[2ACF]\x[2AD0]\x[2AD1]\x[2AD2]\x[2AD3]\x[2AD4]\x[2AD5]\x[2AD6]" ~
    "\x[2AEC]\x[2AED]\x[2AF7]\x[2AF8]\x[2AF9]\x[2AFA]\x[2E02]\x[2E03]\x[2E04]\x[2E05]" ~
    "\x[2E09]\x[2E0A]\x[2E0C]\x[2E0D]\x[2E1C]\x[2E1D]\x[2E20]\x[2E21]\x[2E28]\x[2E29]" ~
    "\x[3008]\x[3009]\x[300A]\x[300B]\x[300C]\x[300D]\x[300E]\x[300F]\x[3010]\x[3011]" ~
    "\x[3014]\x[3015]\x[3016]\x[3017]\x[3018]\x[3019]\x[301A]\x[301B]\x[301D]\x[301E]" ~
    "\x[FE17]\x[FE18]\x[FE35]\x[FE36]\x[FE37]\x[FE38]\x[FE39]\x[FE3A]\x[FE3B]\x[FE3C]" ~
    "\x[FE3D]\x[FE3E]\x[FE3F]\x[FE40]\x[FE41]\x[FE42]\x[FE43]\x[FE44]\x[FE47]\x[FE48]" ~
    "\x[FE59]\x[FE5A]\x[FE5B]\x[FE5C]\x[FE5D]\x[FE5E]\x[FF08]\x[FF09]\x[FF1C]\x[FF1E]" ~
    "\x[FF3B]\x[FF3D]\x[FF5B]\x[FF5D]\x[FF5F]\x[FF60]\x[FF62]\x[FF63]\x[27EE]\x[27EF]" ~
    "\x[2E24]\x[2E25]\x[27EC]\x[27ED]\x[2E22]\x[2E23]\x[2E26]\x[2E27]"#?if js
    ~ nqp::chr(0x2329) ~ nqp::chr(0x232A)#?endif
    ;

下面是它的可视化:

<>[](){}()<>[]{}«»༺༻༼༽᚛᚜‘’‚’‛’“”„”‟”‹›⁅⁆
⁽⁾₍₎∈∋∉∌∊∍∕⧵∼∽≃⋍≒≓≔≕≤≥≦≧≨≩≪≫≮≯≰≱≲≳≴≵≶≷≸≹≺≻≼≽
≾≿⊀⊁⊂⊃⊄⊅⊆⊇⊈⊉⊊⊋⊏⊐⊑⊒⊘⦸⊢⊣⊦⫞⊨⫤⊩⫣⊫⫥⊰⊱⊲⊳⊴⊵⊶⊷⋉⋊
⋋⋌⋐⋑⋖⋗⋘⋙⋚⋛⋜⋝⋞⋟⋠⋡⋢⋣⋤⋥⋦⋧⋨⋩⋪⋫⋬⋭⋰⋱⋲⋺⋳⋻⋴⋼⋶⋽
⋷⋾⌈⌉⌊⌋〈〉⎴⎵❨❩❪❫❬❭❮❯❰❱❲❳❴❵⟃⟄⟅⟆⟕⟖⟝⟞⟢⟣⟤⟥⟦⟧⟨⟩⟪⟫
⦃⦄⦅⦆⦇⦈⦉⦊⦋⦌⦍⦐⦏⦎⦑⦒⦓⦔⦕⦖⦗⦘⧀⧁⧄⧅⧏⧐⧑⧒⧔⧕⧘⧙⧚⧛⧸⧹⧼⧽⨫⨬⨭⨮⨴⨵⨼⨽⩤⩥
⩹⩺⩽⩾⩿⪀⪁⪂⪃⪄⪋⪌⪑⪒⪓⪔⪕⪖⪗⪘⪙⪚⪛⪜⪡⪢⪦⪧⪨⪩⪪⪫⪬⪭⪯⪰⪳⪴⪻⪼⪽⪾⪿⫀⫁⫂
⫃⫄⫅⫆⫍⫎⫏⫐⫑⫒⫓⫔⫕⫖⫬⫭⫷⫸⫹⫺⸂⸃⸄⸅⸉⸊⸌⸍⸜⸝⸠⸡⸨⸩〈〉《》「」『』【】
〔〕〖〗〘〙〚〛〝〞︗︘︵︶︷︸︹︺︻︼︽︾︿﹀﹁﹂
﹃﹄﹇﹈﹙﹚﹛﹜﹝﹞（）＜＞［］｛｝｟｠｢｣⟮⟯⸤⸥⟬⟭⸢⸣⸦⸧

所以，选一个你最喜欢的一对儿括号，让你的同事感到惊讶。

在 HLL::Grammar 的 peek_delimiters 方法中，可以看到以下找到闭合对儿的方法：

my str $stop := $start;my int $brac := nqp::index($brackets, $start);if $brac >= 0 {
    # if it's a closing bracket, that's an error also
    if $brac % 2 {
        self.panic('Use of a closing delimiter for an opener is reserved');
    }

    # it's an opener, so get the closing bracket
    $stop := nqp::substr($brackets, $brac + 1, 1);

它在 $brackets 字符串中查找开口字符，并将下一个字符作为其关闭对儿。 由于最明显的括号位于字符串的开头，其余的不应该影响性能。

༺ 今天就这些了. ༻