クロスメタ演算子を使用すると、** 2と²の動作が異なるのはなぜですか？

カレーでも結果は同じですが、

say map * **2 , 1, 3, 5, 7, 9;
(1 9 25 49 81)
say map *² , 1, 3, 5, 7, 9;
(1 9 25 49 81)

一方、動作はクロスメタオペレーターを介して異なります。

say 1, 3, 5, 7, 9 X**2;
(1 9 25 49 81)
say 1, 3, 5, 7, 9 X²;
((1 2) (3 2) (5 2) (7 2) (9 2))

クロスメタ演算子を使用すると、** 2と²の動作が異なるのはなぜですか？

Xmetaoperatorは、それは彼らがあなたがそれを与える演算子を使ってコンバインを与えられています二つのリストを取ります。指定しない場合は,、デフォルトとして使用される演算子です。

したがって、この場合：

say 1, 3, 5, 7, 9 X²

Xmetaoperatorは中置演算子を探しています。²後置演算子である中置演算子ではありません。

したがって、演算子としてX適用さ,れます。しかし、今²はリストとして評価されており、この場合は「これは2番目」のプロパティです。

基本的にこれらは同じです：

say 1, 3, 5, 7, 9 X²
say 1, 3, 5, 7, 9 X, 2

リスト内のすべてのアイテムを二乗したい場合は、map演算子を使用します。最初と同じように。

一方、IRC

<Doc_Holliwood> m: ².WHAT.say
<camelia> rakudo-moar ed8f5141f: OUTPUT: «(Int)␤»
<Doc_Holliwood> m: say 2 - ²
<camelia> rakudo-moar ed8f5141f: OUTPUT: «0␤»
* abraxxa has quit (Ping timeout: 252 seconds)
<Doc_Holliwood> where is the magic?
<Doc_Holliwood> m: 2².say
<camelia> rakudo-moar ed8f5141f: OUTPUT: «4␤»
<jnthn> I don't think there's any magic at all, it's just falling out of the standard parsing rules
<AlexDaniel> u: ²⅓
<unicodable6> AlexDaniel, U+00B2 SUPERSCRIPT TWO [No] (²)
<unicodable6> AlexDaniel, U+2153 VULGAR FRACTION ONE THIRD [No] (⅓)
<Doc_Holliwood> somewhere something must be actively distinguishing
<AlexDaniel> so any No has a numeric value
<jnthn> Well, the parser knows when it's looking for a term and when it's looking for a postfix
<AlexDaniel> you can use these unicode characters (that are No) as numeric literals
<AlexDaniel> and yeah, what jnthn said :)
<jnthn> It can't be looking for a postfix if it didn't yet see a term
<AlexDaniel> we had a few tickets about this, people find it very surprising, but the parser doesn't
<Doc_Holliwood> so ² is sometimes an int and sometimes its a postfix depending on context?
<tobs> by the same rule, it can distinguish between multiplication and whatever star
<AlexDaniel> well, similarly, yes
<AlexDaniel> m: say (* * *)(2, 8)
<camelia> rakudo-moar ed8f5141f: OUTPUT: «16␤»
<jnthn> Doc_Holliwood: I guess, though only in the same sense that "+" in +$x is the numify operator, but in $a + $b it's the infix addition operator.
<tobs> m: say 2²⁰
<camelia> rakudo-moar ed8f5141f: OUTPUT: «1048576␤»
<jnthn> In general, the parser is always quite clear about what category of thing it would like to see next.
<AlexDaniel> m: 2 2
<camelia> rakudo-moar ed8f5141f: OUTPUT: «===SORRY!=== Error while compiling <tmp>␤Two terms in a row␤at <tmp>:1␤------> 2⏏ 2␤  expecting any of:␤        infix␤        infix stopper␤       statement end␤        statement modifier␤        statement modifier…»
<AlexDaniel> m: * 2
<camelia> rakudo-moar ed8f5141f: OUTPUT: «===SORRY!=== Error while compiling <tmp>␤Two terms in a row␤at <tmp>:1␤------> *⏏ 2␤  expecting any of:␤        infix␤        infix stopper␤       statement end␤        statement modifier␤        statement modifier …»
<AlexDaniel> m: × 2
<camelia> rakudo-moar ed8f5141f: OUTPUT: «===SORRY!=== Error while compiling <tmp>␤Preceding context expects a term, but found infix × instead.␤at > <tmp>:1␤------> ×⏏ 2␤»
<AlexDaniel> the error messages make it quite transparent :)
<Doc_Holliwood> I'm just trying to wrap my head around the latest SO question. but it makes sense to me now. if ² ist a postfix, but X requires an infix. so X² cant DWTHAM
<Doc_Holliwood> in order for say 1, 3, 5, 7, 9 X² to be 1 , 25, etc you would need to change how X works 
*** <jnthn> m: say (1, 3, 5, 7, 9)>>² ***
<camelia> rakudo-moar ed8f5141f: OUTPUT: «(1 9 25 49 81)␤»
<jnthn> Just use something that expects a postfix op :)