Search and replace: Replace substring of match (with substitute(...))

Question

I have a C program where I have to change a 2D array into a 1D array.

What I want is to change this code:

temp[i][j] = (Grid[i][j-1] + Grid[i][j] + Grid[i+1][j] + Grid[i][j+1])/5

to this one:

temp[i*PPE+j] = (Grid[i*PPE+j-1] + Grid[i*PPE+j] + Grid[(i+1)*PPE+j] + Grid[i*PPE+j+1])/5

Because I'm new to Vimscript I split the problem into two parts and tried to tackle the first one:

• [i][j] -> [i*PPE+j]
• [i+1][j+1] -> [(i+1)*PPE+j+1]

I tried the following until now:

:%s#\v[^0-9](\]\[)[a-z][^-+]#\=substitute("\1","*PPE+", "", "")#gc

My reasoning behind this:

• :%s#\v: go through whole file and use magic
• [^0-9](\]\[)[a-z][^-+]: match <nonumber>][<char><not+or-> and () for establishing a group
• \=substitute("\1","*PPE+", "", ""): substitute the first group ( ][ ) with *PPE+
• gc: g for all matches in one line and c for confirmation query

Unfortunately this doesn't seem to work as it replaces i][j] with ^A

Any help with this would be greatly appreciated!

Answer 1

Update

Again, I'm not sure if I fully understand your goal, but the following two commands convert your "before" into your "after":

Handle the i+1 case:

:%s/\v(\D[+-]\d)\]\[/(\1)*PPE+

Do all the rest:

:%s/]\[/*PPE+/g

The first command replaces:

<not-a-digit><plus-or-minus><digit>][

with:

(<captured-group>)*PPE+

The second command simply replaces all remaining instances of ][ with *PPE+.

Original Answer regarding [i][j] only

If I understand your question rightly, I'm not sure if using a sub-replace-expression is the best tool for this job. Perhaps \zs and \ze are better suited to the task?

Try this command:

:%s/\v\D\zs\]\[\ze\D\]/*PPE+

It converts this:

[i][j]
[i+1][j]
[i][j+1]
[i+1][j+1]

To this:

[i*PPE+j]
[i+1][j]
[i][j+1]
[i+1][j+1]

...by matching <not-a-digit>][<not-a-digit>], but setting only the ][ to be included in the match.

Notes:

• \D is easier to type than [^0-9]
• I'm matching a closing ] rather than <not-plus-or-minus>