Proposal: Add list2str() and str2list()

[ichizok]

This pull-req is the part of #4059, which was closed.

list2str(list [, utf8])

• e.g. list2str([0xXXXX, 0xYYYY, 0xZZZZ], 1) == "\uXXXX\uYYYY\uZZZZ" (\uYYYY is a composing character)

str2list(expr [, utf8])

• e.g. str2list("\uXXXX\uYYYY\uZZZZ", 1) == [0xXXXX, 0xYYYY, 0xZZZZ] (\uYYYY is a composing character)

[codecov-io]

Codecov Report

Merging #4190 into master will decrease coverage by <.01%.
The diff coverage is 75%.

@@            Coverage Diff             @@
##           master    #4190      +/-   ##
==========================================
- Coverage   79.34%   79.34%   -0.01%     
==========================================
  Files         105      105              
  Lines      141277   141317      +40     
==========================================
+ Hits       112095   112124      +29     
- Misses      29182    29193      +11

Impacted Files	Coverage Δ
src/evalfunc.c	88.65% <75%> (-0.1%)	⬇️
src/netbeans.c	27.21% <0%> (-0.3%)	⬇️
src/ex_cmds.c	81.68% <0%> (-0.25%)	⬇️
src/ex_cmds2.c	84.89% <0%> (-0.1%)	⬇️
src/window.c	83.05% <0%> (-0.04%)	⬇️
src/gui.c	58.46% <0%> (ø)	⬆️
src/os_unix.c	59.2% <0%> (+0.04%)	⬆️
src/getchar.c	75.46% <0%> (+0.04%)	⬆️
src/channel.c	83.42% <0%> (+0.07%)	⬆️
src/gui_gtk_x11.c	49.45% <0%> (+0.34%)	⬆️
... and 1 more

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[brammool]

This pull-req is the part of #4059, which was closed. list2str(list [, utf8]) * e.g. list2str([0xXXXX, 0xYYYY, 0xZZZZ], 1) == "\uXXXX\uYYYY\uZZZZ" (\uYYYY is a composing character) str2list(expr [, utf8]) * e.g. str2list("\uXXXX\uYYYY\uZZZZ", 1) == [0xXXXX, 0xYYYY, 0xZZZZ] (\uYYYY is a composing character)

I had been wondering whether these functions are useful by themselves. list2str() can be implemented with join() and map(): let str = join(map(list, {nr, val -> nr2char(val)}), '') And str2list(): let list = map(split(str, '\zs'), {idx, val -> char2nr(val)}) So the question is whether this is used often enough to add a function for?

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[ichizok]

let list = map(split(str, '\zs'), {idx, val -> char2nr(val)})

This cannot get unicode composing characters.
e.g. when str = "a\u0300", list contains 0x61 (= 'a') only.

Thus I propose to add str2list() which can get all constituent characters, and the inverse function list2str().
Regarding list2str(), although join(map(...)) can create string including composing characters, it is convenient to be one function corresponding with str2list().