matrix: Remove string tests

[rbasso]

It was argued in #541 that the the exercise would be more interesting without the fromString function, which is not an essential part of of it.

• Rewrite test suite to use [[Int]] instead of String.
• Remove test that wouldn't make sense without fromString.
• Remove all other references to fromString.
• Fix HINTS.md to remove reference to invalid characters.

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Edit:

The scope of this PR was restricted to just removing the last three tests, based on the discussion below. If in the future we decided to completely remove fromString from the test suite, description.md will demand some rewriting.

I think that it is preferable to completely rewrite or remove this exercise. The way it is now is lacks focus and also exposes users to a really unidiomatic interface.

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Closes #541.

[petertseng]

I drew a different conclusion from #541 - I thought that the parsing (in particular, parsing a matrix of ints) was okay, it was simply the tests of parsing a matrix of strings (the two that say "may be tricky") that should have been removed. The matrix of chars probably could go too.

The https://github.com/exercism/x-common/blob/master/exercises/matrix/description.md does mention "given a string with embedded newlines", which does imply that the string parsing was an intended part... just probably not matrices containing non-numbers.

It is true that I wouldn't mind removing the parsing completely (there is already a lot in this exercise) and leaving it for another exercise - please indicate if that is an intended route.

[rbasso]

Oh! When I was reading the exercise I thought that having fromString and representing all matrices as strings in the test suite was so ugly in Haskell that I almost automatically assumed that the complaint was about it.

Right now I'm a little busy, but I can rewrite the PR in a in a day or two.

If anyone want to fix it before that, fell free to open another PR and close this one.

[rbasso]

PR Updated to just remove the three final tests.

[petertseng]

you commented saying remove the final three, but removed only the final two. however, the commit contents are consistent with the commit message (removing tricky string). intentional?

[rbasso]

you commented saying remove the final three, but removed only the final two.

Nice catch, @petertseng. Thanks for checking that!

I guess I forgot to push after deciding to remove the third one.

however, the commit contents are consistent with the commit message (removing tricky string). intentional?

I considered that the third one was also in the trick, so I'm keeping the description. Ok?

[petertseng]

indeed (now only matrices of numbers)

[petertseng]

We forgot to increment the test version (the fourth component)