How to evaluate math expression in matched result of a regular expression in Powershell?

Question

I have a problem about regular expressions. I wonder is it possible to evaluate a math expression on the matched result of a regular expression in powershell? I can't use powershell to evaluate it, only must regex.

Problem Statement:

I have a code something like following:

$id = $reader.GetValue(0).ToString();
$col1 = $reader.GetValue(1).ToString();
$col2 = $reader.GetValue(2).ToString();
$col3 = $reader.GetValue(3).ToString();
$col4 = $reader.GetValue(4).ToString();
$col5 = $reader.GetValue(5).ToString();
$col6 = $reader.GetValue(6).ToString();
$col7 = $reader.GetValue(7).ToString();
...

I need to increase by 3 indexes 0, 1, 2, etc. in GetValue() text with Find & Replace dialog of Powershell ISE.

Result should be like that:

$id = $reader.GetValue(3).ToString();
$col1 = $reader.GetValue(4).ToString();
$col2 = $reader.GetValue(5).ToString();
$col3 = $reader.GetValue(6).ToString();
$col4 = $reader.GetValue(7).ToString();
$col5 = $reader.GetValue(8).ToString();
$col6 = $reader.GetValue(9).ToString();
$col7 = $reader.GetValue(10).ToString();
...

I was try

Find what: GetValue\((\d)\)
Replace with: GetValue($1+3)

But I couldn't success, and I couldn't find any document or reasonable solution about the problem.

Very thanks in advance for any possible solution.

Refactor your code to use an array for the left hand side and a loop and you won't need to do fancy regex to change the starting index — Mat, Sep 17 '21 at 09:58
For parsing mathematical infix notation, see earlier [q&a](https://stackoverflow.com/q/2969561/503046). — vonPryz, Sep 17 '21 at 10:29
Did the answer below help? Please let know if you need more help. — Wiktor Stribiżew, Sep 18 '21 at 09:49
Unfortunately, it is not satisfy my question, because i want to make it with regex. Actually i look for an answer it is possible or not with "only" regex (in 'replace with' part). If there is a way what it is. I also can't still found a solution. — Harun Cetin, Sep 19 '21 at 10:24
I know a solution for **vscode**, `FInd and Transform` an extension I wrote can do this. — Mark, Feb 08 '22 at 22:31

score 1 · Answer 1 · answered Sep 17 '21 at 10:24

You can use

PS> $s = '$col1 = $reader.GetValue(1).ToString();'
PS> $rx = [regex]'(?<=GetValue\()\d+(?=\))'
PS> $rx.Replace($s, { param($m) [int]$m.Value + 1 })
$col1 = $reader.GetValue(2).ToString();

Details:

The regex pattern is compiled as a regex object here
The pattern is re-written to only consume one or more digits, the rest is wrapped with non-consuming lookarounds (a (?<=GetValue$) is a positive lookbehind and (?=$) is a positive lookahead) so that further match manipulation could be simpler
The Regex.Replace method with match evaluator is used, and the { param($m) [int]$m.Value + 1 } part takes the match value (what \d+ matches), casts the string to integer value, adds 1 and the result is put back instead of the digits consumed.

See the regex demo. Details:

(?<=GetValue\() - immediately to the left of the current location, there must be GetValue( text
\d+ - one or more digits
(?=\)) - immediately to the right of the current location, there must be a ) char.

How to evaluate math expression in matched result of a regular expression in Powershell?

1 Answers1