How to turn several "Sqrt [some text inside]" into several Sqrt (some text inside), I mean from [] to ()

Question

I got the following expression that might look like this (the sum of Sqrt [XXX] is unknown)

Sqrt[A+B] + Sqrt[Min[A,B]] * Min[Sqrt[C],D] 

and I want to turn all Sqrt[XXX] into Sqrt(XXX) , I want to replace the brackets [] in Sqrt with () brackets

so the above example will look like

Sqrt(A+B) + Sqrt(Min[A,B]) * Min[Sqrt(C),D]

I don’t want to “harm” the other brackets [] in the expression (for example, next to Min )

How to do this with regex?

Answer 1

You can do this by iterating over characters in a String. First find the Sqrt[ index, and then find the matching closing bracket.

Here is a sample code:

 final String s = "Sqrt[A+B] + Sqrt[Min[A,B]] * Min[Sqrt[C],D]"; final char[] charArray = s.toCharArray(); int index = s.indexOf("Sqrt["); while (index != -1) { final int open = index + 4; charArray[open] = '('; // look for closing bracket int close; int matching = 0; for (close = open + 1; close < charArray.length; close++) { char c = charArray[close]; if (c == ']') { if (matching == 0) { break; } matching--; } else if (c == '[') { matching++; } } charArray[close] = ')'; index = s.indexOf("Sqrt[", index + 1); } System.out.println(new String(charArray)); 

I have not tested it correctly, so please do it.

Answer 2

Using this format of the original string, you can do this with three regular expressions. The trick here is to “rename” the square brackets belonging to the Min function and restore them later. You would do something like:

 s/Min\[([^[]+)\]/Min\{$1\}/g; s/Qsrt\[([^[]+)\]/Sqrt\($1\)/g; s/Min\{([^{]+)\}/Min\[$1\]}/g; 

In general, a parser might go. For special cases, such as using a trick, it may work :-).