From 7bf2aa4054b8378a76dff63acdccbcdad91f68e6 Mon Sep 17 00:00:00 2001 From: Marshall Lochbaum Date: Sat, 7 Aug 2021 20:41:31 -0400 Subject: BREAKING: Don't allow First of empty or reshaping empty to non-empty --- docs/doc/find.html | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'docs/doc/find.html') diff --git a/docs/doc/find.html b/docs/doc/find.html index bc883db2..1421500e 100644 --- a/docs/doc/find.html +++ b/docs/doc/find.html @@ -32,14 +32,14 @@ "string" (≢∘⊢↑⍷) "substring" # APL style ⟨ 0 0 0 1 0 0 0 0 0 ⟩ -

If 𝕨 is larger than 𝕩, the result is empty, and there's no error even in cases where Windows would fail. One place this tends to come up is when applying First (⊑) the result: ⊑⍷ tests whether 𝕨 appears in 𝕩 at the first position, that is, whether it's a prefix of 𝕩. If 𝕨 is longer than 𝕩 it shouldn't be a prefix, so 0 is appropriate.

-↗️
    "loooooong" ⍷ "short"
+
If 𝕨 is larger than 𝕩, the result is empty, and there's no error even in cases where Windows would fail. One place this tends to come up is when applying First (⊑) the result: ⊑⍷ tests whether 𝕨 appears in 𝕩 at the first position, that is, whether it's a prefix of 𝕩. If 𝕨 is longer than 𝕩 it shouldn't be a prefix. First will fail but using a fold 0⊣´⥊∘⍷ instead gives a 0 in this case.

+↗️
    "loooooong" ⍷ "short"
 ⟨⟩
 
     9 ↕ "short"
 ERROR
 
-    ⊑ "loooooong" ⍷ "short"
+    0 ⊣´ "loooooong" ⍷ "short"
 0
 

 
This pattern also works in the high-rank case discussed below, testing whether 𝕨 is a multi-dimensional prefix starting at the lowest-index corner of 𝕩.

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