JuliaLang/julia

replace: allow transform function as first argument?

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#24,598 opened on Nov 13, 2017

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good first issuehelp wantedstrings

Description

The replace function allows a string, an s"..." replacement specifier or a function as its third argument. For the sake of do syntax, it might make sense to support the function as the first argument, like so:

julia> replace("Hello, world.", r"\w+") do word
           n = 0
           for c in word
               n += lowercase(c) in "aeiou"
           end
           return n
       end
"2, 1."

If someone decides to do this, while they're at it, an explanation of replacement patterns – i.e. s"..." strings and some more examples in the replace docs wouldn't hurt. E.g.:

julia> replace("Hello, world.", r"(\w+)(\W+)(\w+)", s"\3\2\1")
"world, Hello."

Contributor guide

Tech stack
None
Domain
backenddocumentation
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Basic Julia knowledgeUnderstanding of replace functionFamiliarity with multiple dispatch
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Examine the current implementation of replace in base/strings.jl. Understand how the function argument is currently handled as the third positional argument. Consider the changes needed to allow it as the first argument for do syntax. Additionally, review the existing documentation for replacement patterns and identify where new examples can be added.