Coloured negative numbers support

[rlewicki]

Hey, following commits contain:

• small fix to also accept whitespaces at the end of an integer in the regex inside is_integer function
• new function that wraps both is_integer and is_double
• new function that checks whether given string is a negative number (either integer or double)
• negative number colour definition for each colour scheme

In the issue #71 @alexhallam you mentioned "add an option". Does this mean you would prefer this to be an optional parameter in the command line? If so, what would the name and short for it be? I'm having a hard time figuring one out 😄

Also, red colour was already used for a NA values so I've used other tone of red if a given scheme had one, otherwise I would use any other colour that is not used. I'm attaching pictures with each scheme presenting how they look like. Let me know if you would rather use other universal colour for all schemes? If not, could you please suggest other tints I can use for that?

Thanks for any feedback up front 🖖

[alexhallam]

I am really excited for this. I just cloned to try it out. I am curious if you are seeing the same coloring I am seeing. Only the first row of negatives are colored

[rlewicki]

Yeah, you are right, there is something off with detecting negative numbers when there is more than one column with numbers. I obviously used a trivial example and assumed it work, silly me 😛 I'll look into it using your example.

Also, I forgot to attach pictures with different colour schemes in original post, sorry.

1. Nord
   
2. OneDark
   
3. Gruvbox
   
4. Dracula
   

[alexhallam]

looks great!

[rlewicki]

I've submitted fix to the case you pointed out. The problem was that sometimes there are whitespaces at the beginning of a text as well. Also f64::from_str was failing due to whitespaces as well, trimming text fixed the issue.
Here is example:

[rlewicki]

@alexhallam I also added tests to cover both new functions just in case. I noticed that @Lireer in #99 added new test section specific for datatypes while I did that in the main file. It might be worth to merge his change first, then I'll move my tests there as well to avoid conflicts.

[alexhallam]

Just wanted to say thanks for all of the issues you have been helping out with. I am reviewing this PR now.

[alexhallam]

trim() is a good idea. Thanks for adding tests!