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diff --git a/doc/replicate.md b/doc/replicate.md index fd53caaf..d41a12c8 100644 --- a/doc/replicate.md +++ b/doc/replicate.md @@ -141,6 +141,6 @@ Finding how many times each index appears in a list of indices is often a useful ≠¨⊔ 2‿2‿4‿1‿2‿0 - /⁼∧ 2‿2‿4‿1‿2‿0 + /⁼ 2‿2‿4‿1‿2‿0 -For `/⁼` to work, the argument has to be sorted: otherwise it won't be a valid result of `/`. But sorting with `∧` is no problem, and `/⁼∧` will probably be faster than `≠¨⊔` in the absence of special handling for either combination. +The last of these is an extension defined in the language specification. As we said, the result of Indices is always sorted, so properly there's no argument that could return `2‿2‿4‿1‿2‿0`. But the index-counting function is very useful, so `/⁼` is defined to implicitly sort its argument (which is still required to be a list of natural numbers). Since `/⁼` is implemented as a single operation, it's the best way to perform this counting task. diff --git a/docs/doc/replicate.html b/docs/doc/replicate.html index 77fcb44e..13dda8d5 100644 --- a/docs/doc/replicate.html +++ b/docs/doc/replicate.html @@ -221,13 +221,13 @@ ⟨ 3 2 1 ⟩ </pre> <p>Finding how many times each index appears in a list of indices is often a useful thing to do, and there are a few ways to do it:</p> -<a class="replLink" title="Open in the REPL" target="_blank" href="https://mlochbaum.github.io/BQN/try.html#code=K8udy5ggKOKGlTUpID3ijJwgMuKAvzLigL804oC/MeKAvzLigL8wICAjIEluZWZmaWNpZW50CgriiaDCqOKKlCAy4oC/MuKAvzTigL8x4oC/MuKAvzAKCi/igbziiKcgMuKAvzLigL804oC/MeKAvzLigL8w">↗️</a><pre> <span class='Function'>+</span><span class='Modifier'>˝˘</span> <span class='Paren'>(</span><span class='Function'>↕</span><span class='Number'>5</span><span class='Paren'>)</span> <span class='Function'>=</span><span class='Modifier'>⌜</span> <span class='Number'>2</span><span class='Ligature'>‿</span><span class='Number'>2</span><span class='Ligature'>‿</span><span class='Number'>4</span><span class='Ligature'>‿</span><span class='Number'>1</span><span class='Ligature'>‿</span><span class='Number'>2</span><span class='Ligature'>‿</span><span class='Number'>0</span> <span class='Comment'># Inefficient +<a class="replLink" title="Open in the REPL" target="_blank" href="https://mlochbaum.github.io/BQN/try.html#code=K8udy5ggKOKGlTUpID3ijJwgMuKAvzLigL804oC/MeKAvzLigL8wICAjIEluZWZmaWNpZW50CgriiaDCqOKKlCAy4oC/MuKAvzTigL8x4oC/MuKAvzAKCi/igbwgMuKAvzLigL804oC/MeKAvzLigL8w">↗️</a><pre> <span class='Function'>+</span><span class='Modifier'>˝˘</span> <span class='Paren'>(</span><span class='Function'>↕</span><span class='Number'>5</span><span class='Paren'>)</span> <span class='Function'>=</span><span class='Modifier'>⌜</span> <span class='Number'>2</span><span class='Ligature'>‿</span><span class='Number'>2</span><span class='Ligature'>‿</span><span class='Number'>4</span><span class='Ligature'>‿</span><span class='Number'>1</span><span class='Ligature'>‿</span><span class='Number'>2</span><span class='Ligature'>‿</span><span class='Number'>0</span> <span class='Comment'># Inefficient </span>⟨ 1 1 3 0 1 ⟩ <span class='Function'>≠</span><span class='Modifier'>¨</span><span class='Function'>⊔</span> <span class='Number'>2</span><span class='Ligature'>‿</span><span class='Number'>2</span><span class='Ligature'>‿</span><span class='Number'>4</span><span class='Ligature'>‿</span><span class='Number'>1</span><span class='Ligature'>‿</span><span class='Number'>2</span><span class='Ligature'>‿</span><span class='Number'>0</span> ⟨ 1 1 3 0 1 ⟩ - <span class='Function'>/</span><span class='Modifier'>⁼</span><span class='Function'>∧</span> <span class='Number'>2</span><span class='Ligature'>‿</span><span class='Number'>2</span><span class='Ligature'>‿</span><span class='Number'>4</span><span class='Ligature'>‿</span><span class='Number'>1</span><span class='Ligature'>‿</span><span class='Number'>2</span><span class='Ligature'>‿</span><span class='Number'>0</span> + <span class='Function'>/</span><span class='Modifier'>⁼</span> <span class='Number'>2</span><span class='Ligature'>‿</span><span class='Number'>2</span><span class='Ligature'>‿</span><span class='Number'>4</span><span class='Ligature'>‿</span><span class='Number'>1</span><span class='Ligature'>‿</span><span class='Number'>2</span><span class='Ligature'>‿</span><span class='Number'>0</span> ⟨ 1 1 3 0 1 ⟩ </pre> -<p>For <code><span class='Function'>/</span><span class='Modifier'>⁼</span></code> to work, the argument has to be sorted: otherwise it won't be a valid result of <code><span class='Function'>/</span></code>. But sorting with <code><span class='Function'>∧</span></code> is no problem, and <code><span class='Function'>/</span><span class='Modifier'>⁼</span><span class='Function'>∧</span></code> will probably be faster than <code><span class='Function'>≠</span><span class='Modifier'>¨</span><span class='Function'>⊔</span></code> in the absence of special handling for either combination.</p> +<p>The last of these is an extension defined in the language specification. As we said, the result of Indices is always sorted, so properly there's no argument that could return <code><span class='Number'>2</span><span class='Ligature'>‿</span><span class='Number'>2</span><span class='Ligature'>‿</span><span class='Number'>4</span><span class='Ligature'>‿</span><span class='Number'>1</span><span class='Ligature'>‿</span><span class='Number'>2</span><span class='Ligature'>‿</span><span class='Number'>0</span></code>. But the index-counting function is very useful, so <code><span class='Function'>/</span><span class='Modifier'>⁼</span></code> is defined to implicitly sort its argument (which is still required to be a list of natural numbers). Since <code><span class='Function'>/</span><span class='Modifier'>⁼</span></code> is implemented as a single operation, it's the best way to perform this counting task.</p> @@ -16,7 +16,7 @@ WParse←{ na←(2×sep)+f×1+l↑0∾c∨v d←+`o-c⋄fe←(+`⌾((⍋d)⊸⊏)o)⊏l∾(⍋⊏⟜d)⊸⊏/c fe⌊↩l-l↑⌽⌈`↕∘≠⊸×⌽1∾˜sep - sel←¬∘⊏⟜(o∨c)⊸/⍋((f×fe)⌈↕l)-+`f-l↑/⁼∧f/fe + sel←¬∘⊏⟜(o∨c)⊸/⍋((f×fe)⌈↕l)-+`f-l↑/⁼f/fe sel⊸⊏¨𝕩‿na } |