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duplicates list edited from Using Position (which requires a pattern) in the same manner as Select (which requires a criterion) to Using Position (which requires a pattern) in the same manner as Select (which requires a criterion), Pattern matching not going over a list when using default values

edited Sep 26, 2017 at 21:23

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Post Closed as "Duplicate" by Mr.Wizard pattern-matching

Using Position (which requires a pattern) in the same manner as Select (which requires a criterion)

occurred Sep 26, 2017 at 21:23

Tweeted twitter.com/StackMma/status/912680627819958274

occurred Sep 26, 2017 at 14:09

edited tags

edited Sep 26, 2017 at 10:27

J. M.'s missing motivation

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pattern-matching replacement

asked Sep 26, 2017 at 10:20

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Unexpected behavior using `ReplaceAll[]` for nested lists

ReplaceAll[] might lead to unexpected behavior (at least it surprised me). I use ReplaceAll[] to convert a list (basically data cleanup).

For the command:

{{1, "2"}, {2, "3"}} /. {x_, _ } :> {x, "SOMETHING"}

I expected

{{1, "SOMETHING"}, {2, "SOMETHING"}}

but got

{{1, "2"}, "SOMETHING"}.