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diff --git a/docs/doc/fill.html b/docs/doc/fill.html index b4ac35ef..e350fa6e 100644 --- a/docs/doc/fill.html +++ b/docs/doc/fill.html @@ -4,10 +4,10 @@ <title>BQN: Fill elements</title> </head> <div class="nav">(<a href="https://github.com/mlochbaum/BQN">github</a>) / <a href="../index.html">BQN</a> / <a href="index.html">doc</a></div> -<h1 id="fill-elements">Fill elements</h1> +<h1 id="fill-elements"><a class="header" href="#fill-elements">Fill elements</a></h1> <p>A few array operations need an array element to use when no existing element applies. BQN tries to maintain a "default" element for every array, known as a fill element, for this purpose. If it's known, the fill element is a nested array structure where each atom is either <code><span class='Number'>0</span></code> or <code><span class='String'>' '</span></code>. If no fill is known, a function that requests it results in an error.</p> <p>Fills are used by <a href="take.html">Take</a> (<code><span class='Function'>↑</span></code>) when a value in <code><span class='Value'>𝕨</span></code> is larger than the corresponding length in <code><span class='Value'>𝕩</span></code>, by the two <a href="shift.html">Nudge</a> functions (<code><span class='Function'>»«</span></code>) when <code><span class='Value'>𝕩</span></code> is non-empty, by <a href="couple.html">Merge</a> (<code><span class='Function'>></span></code>) when <code><span class='Value'>𝕩</span></code> is empty, and by <a href="reshape.html">Reshape</a> (<code><span class='Function'>⥊</span></code>) when <code><span class='Value'>𝕨</span></code> contains <code><span class='Function'>↑</span></code>. Except for these specific cases, the fill value an array has can't affect the program. The result of <a href="match.html">Match</a> (<code><span class='Function'>≡</span></code>) doesn't depend on fills, and any attempt to compute a fill can't cause side effects.</p> -<h2 id="using-fills">Using fills</h2> +<h2 id="using-fills"><a class="header" href="#using-fills">Using fills</a></h2> <p>For the examples in this section we'll use the fact that an all-number array usually has <code><span class='Number'>0</span></code> as a fill while a string has <code><span class='String'>' '</span></code> (BQN maintains fills alongside array values rather than deriving them from arrays, so it's possible to construct arrays where this isn't true, but this probably wouldn't happen in ordinary code).</p> <p><a href="take.html">Take</a> (<code><span class='Function'>↑</span></code>) and <a href="shift.html">Nudge</a> (<code><span class='Function'>»«</span></code>) in either direction use the fill for padding, to extend the array past its boundary. For example, <code><span class='Value'>𝕨</span><span class='Function'>↑</span><span class='Value'>𝕩</span></code> will add elements to one side when a number in <code><span class='Function'>|</span><span class='Value'>𝕨</span></code> is larger than the corresponding length in <code><span class='Function'>≢</span><span class='Value'>𝕩</span></code>.</p> <a class="replLink" title="Open in the REPL" target="_blank" href="https://mlochbaum.github.io/BQN/try.html#code=wq83IOKGkSA04qWKMyAgICAgIyBGaWxsIHdpdGggMAoKwq83IOKGkSAicXJzdCIgICMgRmlsbCB3aXRoIHNwYWNl">↗️</a><pre> <span class='Number'>¯7</span> <span class='Function'>↑</span> <span class='Number'>4</span><span class='Function'>⥊</span><span class='Number'>3</span> <span class='Comment'># Fill with 0 @@ -38,7 +38,7 @@ <a class="replLink" title="Open in the REPL" target="_blank" href="https://mlochbaum.github.io/BQN/try.html#code=4oqRwrsx4oaR4qWKInN0cmluZyI=">↗️</a><pre> <span class='Function'>⊑»</span><span class='Number'>1</span><span class='Function'>↑⥊</span><span class='String'>"string"</span> ' ' </pre> -<h2 id="how-fills-are-computed">How fills are computed</h2> +<h2 id="how-fills-are-computed"><a class="header" href="#how-fills-are-computed">How fills are computed</a></h2> <p>For the exact requirements placed on fill, see <a href="../spec/inferred.html#fill-elements">the specification</a> (particularly "required functions"). This section loosely describes behavior in existing BQN implementations, and includes some parts that aren't required in the specification.</p> <p>A fill element should encompass something that's necessarily true for all elements of an array. If the way an array is computed implies it's all numbers, the fill should be <code><span class='Number'>0</span></code>. If every element is a list of two numbers, then the fill should be <code><span class='Bracket'>⟨</span><span class='Number'>0</span><span class='Separator'>,</span><span class='Number'>0</span><span class='Bracket'>⟩</span></code>. If every element is a list but the lengths might vary, <code><span class='Bracket'>⟨⟩</span></code> is probably a reasonable fill element.</p> <p>For <a href="arithmetic.html">arithmetic</a> primitives, the fill is found by the rules of pervasion, applying the function to both argument fills. Generally this means it consists of <code><span class='Number'>0</span></code>, but character arithmetic also allows space fills.</p> |