Insert carriage return in a vimscript variable

Question

A vimscript variable longstring (for instance obtained by let longstring = getline('.')) contains a long sequence of characters (numbers, letters, commas, spaces, ...).

I want to replace a specific character, let it be A, with a carriage return, so that when I use call writefile(longstring, 'this.file', '') I obtain a file with several lines, each containing what was found between two consecutive As.

I tried with let longstring = substitute(longstring,'A','\r','g'), which only results (after writefile) in a single long line file with ^M in place of A. I guess I'm using the wrong replace string, but \n doesn't work either.

Answer 1

The first argument of writefile must be a list and each list item represents a line in the new file.

Using split() you could make a pattern-separated list out of longstring as follows:

call writefile(split(longstring, "A"), 'this.file', '')

and obtain the intended result.