Vim search replace regex + incremental function - regex

Question

I'm currently stuck in vim trying to find a search/replace oneliner to replace a number with another + increment for each new iteration = when it finds a new match.
I'm working in xml svg code to batch process files Inkscape cannot process the text (plain svg multiline text bug).
<tspan
x="938.91315"
y="783.20563"
id="tspan13017"
style="font-weight:bold">Text1:</tspan><tspan
x="938.91315"
y="833.20563"
id="tspan13019">Text2</tspan><tspan
x="938.91315"
y="883.20563"
id="tspan13021">✗Text3</tspan>
etc.
So what I want to do is to change that to this result:
<tspan
x="938.91315"
y="200"
id="tspan13017"
style="font-weight:bold">Text1:</tspan><tspan
x="938.91315"
y="240"
id="tspan13019">Text2</tspan><tspan
x="938.91315"
y="280"
id="tspan13021">✗Text3</tspan>
etc.
So I duckducked and found the best vim tips resource from zzapper, but I cannot understand it:
convert yy to 10,11,12 :
:let i=10 | ’a,’bg/Abc/s/yy/\=i/ |let i=i+1
I then adapted it to something I can understand and should work in my home vim:
:let i=300 | 327,$ smagic ! y=\"[0-9]\+.[0-9]\+\" ! \=i ! g | let i=i+50
But somehow it doesn't loop, all I get is that:
<tspan
x="938.91315"
300
id="tspan13017"
style="font-weight:bold">Text1:</tspan><tspan
x="938.91315"
300
id="tspan13019">Text2</tspan><tspan
x="938.91315"
300
id="tspan13021">✗Text3</tspan>
So here I'm seriously stuck. I cannot figure out what doesn't work :
My adaptation of the original formula ?
My data layout ?
My .vimrc ?
I'll try to find other resources by myself, but on that kind of trick they are pretty rare I find, and like in zzapper tips, not always delivered with a manual.

Answer 1

One way to fix it:
:let i = 300 | g/\m\<y=/ s/\my="\zs\d\+.\d\+\ze"/\=i/ | let i += 50
Translation:
let i = 300 - hopefully obvious
g/\m\<y=/ ... - for all lines matching \m\<y=, apply the following command; the "following command" is s/.../.../ | let ...; the regexp:
\m - "magic" regexp
\< - match only at word boundary
s/\my="\zs\d\+.\d\+\ze"/\=i/ - substitute; the regexp:
\m - "magic" regexp
\d\+ - one or more digits
\zs...\ze - replace only what is matched between these points
\=i - replace with the value of expression i
let i += 50 - hopefully obvious again.
For more information: :help :g, :help \zs, :help \ze, help s/\\=.

Answer 2

Just to add my take as a memo (wrote this as an answer as an EDIT didn't seem right). Sorry it is not the best vim scripting here but it enables me to understand (I'm not a vim specialist).
:let i=300 | 323,$g/y="/smagic![0-9]\+.[0-9]\+!\=i!g | let i+=50
Assign the initial value to i :
:let i=300
Start :global (:g) function from line 323 to the end of file:
323,$g
Pattern to match for executing the commands (litteral text here)
y="
Substitution with magic on (magic meaning special characters "enabled")
smagic
Pattern to find
[0-9]\+.[0-9]\+
(numbers between 0-9 one or more times, a litteral dot, the numbers again)
Replaced with
\=i
\= tells vim to evaluate i not to write it litterally
Increment i with 50 for the next iteration
let i+=50
This part is still in the g function.
The separators, in bold:
| are the separators between the different functions
/ are the separators in the :g function
! are the separators in the smagic function