Re: Can you loop in math mode?

[Sebastian Gniazdowski <sgniazdowski@xxxxxxxxx>]

I'm writing a function that computes lengths of the lines in BUFFER
and builds up an array, where each element is a sum of the previous
and the current line / element.

So I have:

integer idx sum
lines_lengths=( ${lines_lengths[@]/(#m)*/$(( sum += ${#MATCH}+1 ))} )

However, I would also like to take into account screen lines, so i.e.
gradually decline ${#MATCH} by COLUMNS bit by bit, assigning a new
element also for each screen-line. Like the following function does:

.zed-compute-llen() {
    len=${#1}
    while (( len > COLUMNS )) {
        sum+=COLUMNS
        lines_lengths[++idx]=( $sum )
        len=len-COLUMNS
    }
    sum+=len+1
    lines_lengths[++idx]=( $sum )
}

So basically, I would want to do this in the // substitution, like so:

: ${lines_lengths[@]/(#m)*/$(( append(${#MATCH}) ))}

which now thus just resolved :] I don't even need the string-math
function, append should add multiple lines_lengths elements if len >
COLUMNS, that's all.

But thanks for the answer, I think I could use recursion for this too.

On Mon, 19 Aug 2019 at 08:20, Stephane Chazelas
<stephane.chazelas@xxxxxxxxx> wrote:
>
> 2019-08-19 02:16:20 +0200, Sebastian Gniazdowski:
> [...]
> > is some kind of a looping possible in math mode?
> [...]
>
> Can you maybe be more specific as to what you're trying to do?
>
> You can use recursion:
>
> $ n=6 a='(n-->1 ? a*(n+1) : 1)' zsh -c 'echo $((a))'
> 720
>
> (6!)
>
> Including via math functions, but within limits.
>
> $ n=0 a='(++n <= 255 ? a+2 : 1)' zsh -c 'echo $((a))'
> zsh:1: math recursion limit exceeded: (++n <= 255 ? a+2 : 1)
>
> And you can of course have command substitutions inside an
> arithmetic expression:
>
> $ echo $(( 1 $(for i ({2..6}) print "*$i") ))
> 720
>
> --
> Stephane



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