From bed78fe6147cb7921b7367960d406d28d37cb019 Mon Sep 17 00:00:00 2001 From: Marshall Lochbaum Date: Tue, 7 Jun 2022 22:16:01 -0400 Subject: The editing is going to end at some point isn't it? --- docs/doc/search.html | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) (limited to 'docs/doc/search.html') diff --git a/docs/doc/search.html b/docs/doc/search.html index 2e75dc97..a92b25c1 100644 --- a/docs/doc/search.html +++ b/docs/doc/search.html @@ -89,7 +89,7 @@ -

The three search functions are Index of (⊐), Progressive Index of (βŠ’), and Member of (∊). These are dyadic functions that search one argument ("searched-in") for major cells matching cells from the other ("searched-for"). For example, Index of returns, for each cell in 𝕩, the index of the first cell in 𝕨 that matches it.

+

The three search functions are Index of (⊐), Progressive Index of (βŠ’), and Member of (∊). These are dyadic functions that search one argument ("searched-in") for major cells matching cells from the other ("searched-for"). For example, Index of returns, for each cell in 𝕩, the index of the first cell in 𝕨 that matches it.

@@ -153,7 +153,7 @@ ⟨ 1 4 2 ⟩

π•©βˆŠπ•¨ is the same as (π•¨βŠπ•©)<≠𝕨. Note the reversal of arguments! In both ∊ and ⊐, the open side points to the searched-in argument and the closed side points to the searched-for argument. Relatedly, in Select (⊏), the open side points to the selected argument, which is more like the searched-in argument in that its cells are generally accessed out of order (the searched-for argument is most like the selection result π•¨βŠπ•©).

-

Index of always returns exactly one number, even if there are multiple matches, or no matches at all. To find the indices of all matches, start with Match Each, then Indices (I didn't mean for it to sound so repetitive! It just happened!).

+

Index of always returns exactly one number, even if there are multiple matches, or no matches at all. To find the indices of all matches, start with Match Each, then apply Indices (I didn't mean for it to sound so repetitive! It just happened!).

↗️
    / "letters" ≑¨< 'e'        # Many to one
 ⟨ 1 4 ⟩
 
@@ -161,7 +161,7 @@
 ⟨ ⟨ 0 ⟩ ⟨ 1 4 ⟩ ⟨ 2 3 ⟩ ⟩

Progressive Index of

-

Progressive Index of (βŠ’), as the name and glyph suggest, is a more sophisticated variant of Index of. Like Index of, it returns either ≠𝕨 or an index of a cell from 𝕨 that matches the given cell of 𝕩. Unlike Index of, no index except ≠𝕨 can ever be repeated. Progressive Index of returns the index of the first unused match, provided there's still one left.

+

Progressive Index of (βŠ’), as the name and glyph suggest, is a more sophisticated variant of Index of. Like Index of, it returns either ≠𝕨 or an index of a cell from 𝕨 that matches the given cell of 𝕩. Unlike Index of, no index can ever be repeated (but ≠𝕨 can). Progressive Index of returns the index of the first unused match, provided there's still one left.

↗️
    "aaa" βŠ’ "aaaaa"
 ⟨ 0 1 2 3 3 ⟩
 
@@ -209,7 +209,7 @@
 Β· 2  
     β”˜
-

Just as bad, this result has the right information, but is enclosed and could break the program later on. Remember that the result of a search function is always an array. We really want the first element.

+

This result has the right information, but is enclosed and could break the program later on. Remember that the result of a search function is always an array. We really want the first element.

↗️
    stuff βŠ‘βˆ˜βŠβŸœ< "string"
 2
@@ -235,7 +235,7 @@ β”˜

But the searched-in argument doesn't have to be a list either! It can also be an array of higher rank. Rank 0 isn't allowed: if you want to "search" a unit, you're probably just looking for match.

-

The searched-in argument is treated as a list of its major cells. It's the rank of these major cellsβ€”let's call this rank cβ€”that determines how the searched-for argument is treated. That argument must have rank c or more, and it's treated as an array of c-cells. For example, if the left argument to ⊐ is a rank-2 table, then each 1-cell (row) of 𝕩 is searched for independently, yielding one number in the result: a 0-cell.

+

The searched-in argument is treated as a list of its major cells. It's the rank of these major cellsβ€”let's call this rank cβ€”that determines how the searched-for argument is treated. That argument must have rank c or more, and it's treated as an array of c-cells. For example, if the left argument to ⊐ is a rank-2 table, then each 1-cell (row) of 𝕩 is searched for independently, yielding one number in the result: a 0-cell.

↗️
    ⊒ rows ← >"row"β€Ώ"rho"β€Ώ"row"β€Ώ"rue"
 β”Œβ”€     
 β•΅"row  
@@ -251,7 +251,7 @@
         β”˜

So the result rank of ⊐ is always 𝕨¬○=𝕩, with a result shape (1-˜=𝕨)↓≒𝕩, and π•¨βŠπ•© fails if 1>=𝕩 or the result rank would be negative. In the list case, we have 1==𝕩 (so the first condition holds), and the result rank resolves to =𝕨 (which can't be negative, so the second holds as well). The cell rank of 𝕩 is 0, and the fact that a 0-cell of 𝕩 gives a 0-cell of the result is what causes the shape arithmetic to be so simple.

-

For Member of, the arguments are reversed relative to Index of, but otherwise everything's the same. This differs from APL, where entries are always elements, not cells. Many APL designers consider the APL definition to be a failure of foresight and would prefer BQN's definitionβ€”or rather A+'s or J's definition, as these languages were actually the first to use it. The rank-aware version is more flexible, as it allows both searching for elements and searching for rows. APL would return the first result in both cases.

+

For Member of, the arguments are reversed relative to Index of, but otherwise everything's the same. This differs from APL, where entries are always elements, not cells. Many APL designers consider the APL definition to be a failure of foresight and would prefer BQN's definitionβ€”or rather A+'s or J's definition, as these languages were actually the first to use it. The rank-aware version is more flexible, as it allows both searching for elements and searching for rows. APL would return the first result in both cases below.

↗️
    (2β€Ώ1≍3β€Ώ1) ∊ 3β€Ώ1β€Ώ4β€Ώ3
 β”Œβ”€     
 β•΅ 0 1  
-- 
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