From f31934418dadd7fd7e5ea31634a40d3e9e4edfdc Mon Sep 17 00:00:00 2001 From: Marshall Lochbaum Date: Thu, 21 Jan 2021 20:41:53 -0500 Subject: Fill for a string literal is a character --- docs/spec/inferred.html | 1 + 1 file changed, 1 insertion(+) (limited to 'docs/spec') diff --git a/docs/spec/inferred.html b/docs/spec/inferred.html index 34d4725d..251c35c4 100644 --- a/docs/spec/inferred.html +++ b/docs/spec/inferred.html @@ -71,6 +71,7 @@

Fill elements

Any BQN array can have a fill element, which is a sort of "default" value for the array. The reference implementations use Fill to access this element, and it is used primarily for Take (↑), First (⊑), and Nudge («, »). One way to extract the fill element of an array a in BQN is ⊑0⥊a.

A fill element can be either 0, ' ', or an array of valid fill elements. If the fill element is an array, then it may also have a fill element (since it is an ordinary BQN array). The fill element is meant to describe the shared structure of the elements of an array: for example, the fill element of an array of numbers should be 0, while the fill element for an array of variable-length lists should probably be ⟨⟩. However, the fill element, unlike other inferred properties, does not satisfy any particular constraints that relate it to its array.

+

In addition to the requirements below, the fill element for the value of a string literal is ' '.

Required functions

Combinators ⊣⊢!˙˜´˝∘○⊸⟜⊘◶⍟ do not affect fill element computation: if the combinator calls a function that computes a fill element, then that fill element must be retained if the result is passed to other functions or returned. ⍟ constructs arrays if its right operand is or contains arrays, and the fill elements of these arrays are not specified; converting 𝕩 to a fill element is a reasonable choice in some cases but not others.

Arithmetic primitives—all valences of +-×÷⋆√⌊⌈|¬∧∨ and dyadic <>≠=≤≥—obtain their fill elements by applying to the fill elements of the arguments. If this is an error, there is no fill element; otherwise, the fill element is the result, with all numbers in it changed to 0 and all characters changed to ' '.

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