JuliaLang/julia

searchsorted by applies by function to item being searched

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#9,429 opened on 2014年12月21日

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help wantedsearch & find

説明

Consider this:

using Base.Dates: Second

immutable tsp # time series point
    t :: DateTime
    y :: Float64
end

t0 = now()
S = [tsp(t0+Second(10), 42), tsp(t0+Second(13), -1), tsp(t0+Second(17), 31)]

searchsortedfirst(S, t0+Second(12), by=x -> x.t)
searchsortedfirst(S, tsp(t0+Second(12), NaN), by=x -> x.t)

The first search call fails and the second is not ideal because one has to use a dummy value (NaN here) to fill in the parts of the item being searched that are not part of the key. I think that in searchsortedfirst(S, x, by=f) it would make more sense to apply f() to the items of S but not to the item x. If the searchsorted functions worked like that, then the current behavior is easily obtained by using searchsortedfirst(S, f(x), by=f). Inversion of f() is not necessarily as easy.

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技術スタック
なし
領域
api
Issue 種別
feature
難度新しい貢献者にとっての実装難度です。1 は非常に小さな変更、5 は専門的な作業です。
3
推定時間経験ある貢献者が調査、実装、テスト、pull request 準備にかけるおおよその時間範囲です。
1-2 days
活動状況Issue が今どれだけ取り組みやすいかを示します。新しい、活発、古い、ブロック中、またはメンテナー入力待ちなどです。
stale
明確さ期待される変更、受け入れ条件、次の手順がどれだけ明確かを示します。
mostly clear
前提条件
understanding of Julia's searchsorted functionsfamiliarity with Julia base library
初心者向け度初回貢献者にどれだけ取り組みやすいかを 1-100 で推定したスコアです。
20
調査方針
The issue proposes changing searchsorted functions so that the 'by' function applies only to elements of the collection, not to the searched item. This would require modifying the implementation in base/sort.jl or similar. The discussion in the comments (e.g., @StefanKarpinski's input) should be reviewed to understand potential implications. Consider testing edge cases and ensuring backward compatibility.