Talk:Brace expansion using ranges: Difference between revisions

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→‎Flippin' 'eck

Nigel Galloway

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Revision as of 18:06, 26 August 2020 (view source) Hout (talk \| contribs) (→‎Out of curiosity – stepped Alpha seen working in the (unix shell) wild ?) ← Older edit		Latest revision as of 16:10, 7 October 2021 (view source) Nigel Galloway (talk \| contribs) (→‎Flippin' 'eck)
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Line 8: : Ah. Got it. It's because the macOS Catalina distribution of Bash turns out to be 3.2, rather than 4. [[User:Hout\|Hout]] ([[User talk:Hout\|talk]]) 18:06, 26 August 2020 (UTC) ===Flippin' 'eck=== What is the behaviour of echo {1..6..-2} using zsh shell on macOS Catalina? Using Linux bash 5.1 it is 1 3 5. Should flipped be 5 3 1 or 6 4 2? It is bad enough when task descriptions require one to debug Python to make sense of it but zsh shell on macOS Catalina, come on.--[[User:Nigel Galloway\|Nigel Galloway]] ([[User talk:Nigel Galloway\|talk]]) 14:31, 27 September 2021 (UTC) : Good point. On zsh 5.8 (macOs – x86_64-apple-darwin20.0), the expansion of {1..6..-2} turns out to be [5,3,1] ... : Perhaps zsh is just not a sufficiently well-defined or consistently implemented target for such a task ? : Do you know of an arguably canonical implementation of zsh (or some other widely used shell), with well-defined and consistent enumeration rules which we could formally summarize and illustrate here ? [[User:Hout\|Hout]] ([[User talk:Hout\|talk]]) 18:07, 28 September 2021 (UTC) : PS I am slow at the best of times, but I still haven't quite understood the macOS zsh {1..6..-2} -> [5,3,1] logic, which I hadn't noticed before ... : [[User:Hout\|Hout]] ([[User talk:Hout\|talk]]) 18:12, 28 September 2021 (UTC) : Ah, I see. Starting at one, with intervals of 2, and the whole sequence reversed. [[User:Hout\|Hout]] ([[User talk:Hout\|talk]]) 18:15, 28 September 2021 (UTC) ::I have added F# based on this discussion, and see that Python has been added using the other possible meaning of flip. No other solutions currently have examples where the meaning of flip is ambiguous. The task description needs updating to: disambiguate flip; include appropriate examples of flipped ranges and a warning added that the task description has changed and solutions may need modifying.--[[User:Nigel Galloway\|Nigel Galloway]] ([[User talk:Nigel Galloway\|talk]]) 13:55, 6 October 2021 (UTC) :::Thanks – that's very helpful. :::What's the best tag or other method for drawing attention to an additional test, :::and warning that modifications may be needed ? :::[[User:Hout\|Hout]] ([[User talk:Hout\|talk]]) 20:25, 6 October 2021 (UTC) ::::Perhaps see Dijkstra's algorithm.--[[User:Nigel Galloway\|Nigel Galloway]] ([[User talk:Nigel Galloway\|talk]]) 16:10, 7 October 2021 (UTC)