Add generic DisplayString function

[danielrademacher]

Start of PR which Resolves #5144

Text for release notes

none

[fingolfin]

You write that this "fixes" (should perhaps be: "resolves" ?) issue #5144, but as far as I can tell, it only addresses part of it?

[fingolfin]

Add a test case?

[danielrademacher]

Will be done. Which file would you prefer?

[danielrademacher]

How should we deal with numbers of different length, i.e.

gap> m:=NewMatrix(IsPlistMatrixRep,Rationals,2,[-1,-2,0,-4]);;
gap> Print(DisplayString(m));
<a mutable 2x2-matrix over Rationals [
[-1 -2]
[0 -4]
]>

[ChrisJefferson]

While I realise this would require significantly changing how your code is structured, one way to fix the "numbers of different length" would be to first make a 2d array of strings representing what you are going to print, then finding the maximum length of a string in that 2d array, and finally printing. Nicely formatting is going to require going over the matrix twice whatever you do (first time to get length, second time to output).

[fingolfin]

You could also take a look PrintArray and either just call that, or take inspiration from that code.

[danielrademacher]

You could also take a look PrintArray and either just call that, or take inspiration from that code.

Thanks a lot! The PrintArray code inspired me to write this new version. 😁

[ChrisJefferson]

Just checking, what's the state of this PR, does it want reviewing?

I don't mind if you are still working on it, just didn't want it to get ignored.