With[{a=1},{b=a},b] in 13.2 does evaluate to 1

Asked Apr 22 '23 at 09:23

Active Apr 22 '23 at 09:23

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This isn't documented, and the front end highlights the second comma and third argument in red, but it's used in DownValues[Once][[3]] and is very convenient. Anyone know more?

asked Apr 22 '23 at 09:23

Edward Huff

6

Does this answer your question? How to avoid nested With[]? -- See this answer in particular. – Michael E2 Apr 22 '23 at 10:28
Getting proper syntax coloring is apparently not a trivial undertaking. Until that happens I doubt it will be documented. But the change that allowed this syntax is intended to be permanent. – Daniel Lichtblau Apr 22 '23 at 15:07
I think two comments, by István Zachar and Daniel Lichtblau are worth cross-referencing, as is IterateWith. "Normally, later With variables are unaware of earlier variables’ values". Compare With[{a = 3, b = a + 2, c = a + b}, {a, b, c}] to With[{a = 3}, {b = a + 2}, {c = a + b}, {a, b, c}] ... – user1066 Apr 22 '23 at 18:35
.... But why is this not better documented? A similar comment could be applied to obtaining a stable sort – user1066 Apr 22 '23 at 18:36

With[{a=1},{b=a},b] in 13.2 does evaluate to 1

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