feat: add string comparison support

[eddycharly]

Add string comparison support.

Fixes #96

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.81%. Comparing base (e430401) to head (9f8a53f).
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #99      +/-   ##
==========================================
+ Coverage   88.51%   90.81%   +2.29%     
==========================================
  Files          15       15              
  Lines        2594     2220     -374     
==========================================
- Hits         2296     2016     -280     
+ Misses        204      112      -92     
+ Partials       94       92       -2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[eddycharly]

@springcomp do we have a test suite for that ?

[eddycharly]

@springcomp WDYT about returning an error here ?

[springcomp]

My understanding is that this is already covered in the original code by returning nil, nil.
As this is a non-standard extension, I think we should return that as well if types do not match.

I like the attempt to cast as numbers and compare that.
This means that comparing number-like strings will produce the correct output.

Please, be aware that comparing strings may still exhibit confusing output.
For instance the following two strings will not be considered equal:

• élément (é LATIN SMALL LETTER E WITH ACUTE ACCENT (U+00E9), …
• élément (e LATIN SMALL LETTER E (U+0065), ◌́ COMBINING ACUTE ACCENT (U+0301), …

[springcomp]

My understanding is that this is already covered in the original code by returning nil, nil.
As this is a non-standard extension, I think we should return that as well if types do not match.

I like the attempt to cast as numbers and compare that.
This means that comparing number-like strings will produce the correct output.

Please, be aware that comparing strings may still exhibit confusing output.
For instance the following two strings will not be considered equal:

• élément (é LATIN SMALL LETTER E WITH ACUTE ACCENT (U+00E9), …
• élément (e LATIN SMALL LETTER E (U+0065), ◌́ COMBINING ACUTE ACCENT (U+0301), …

[eddycharly]

I think it's a good first step but we definitely need a conformance test suite IMHO.

As this is a non-standard extension

What do you mean by non-standard ?

[springcomp]

What do you mean by non-standard ?

In the specification, ordering operators are only specified for numbers.
Comparing any other consistently-typed items, or even heterogeneously-typed items, is currently unspecified.

A library is free (and more than welcome) to include non-standard features or improvement of course.
We just need to be wary to not go in a direction that would need an overhaul in the future if new specifications come in for the same subject.

[springcomp]

@eddycharly I think this is in good share.
Is there anything you still need for this PR to be merged ?