rna-transcription: Is the new version with Maybe too hard to be at the start of the track?

[rbasso]

After #168 (#166), I think that rna-transcription may be out of place.

To solve it, the user needs to work with a list of Maybes, but beginners don't seem to understand sequence and traverse easily.

A good starter exercise with Maybe would be great, but I think that rna-transcription demands more advanced knowledge.

I propose to move it further in the track as soon as possible, to avoid loosing new users stuck at the third exercise.

[rbasso]

Is rna-transcrption in a good position in the track or should we move it?

What do you think about it, @samjonester ?
I would love to hear your opinion on this one @petertseng!

I already asked 6 users what they think about the new version but I still don't have the answers.

Edit:

• One user was able to solve it with the help of Hoogle, but had not idea about how mapM worked.
• Another user avoided traverse validating the sequence with all isValidNucleotide.

[samjonester]

That sounds like a good idea. It's not as difficult as phone number or nucleotide count, so I think it should come before them. Alternatively, it could be moved to be by hamming / space age.

[samjonester]

Also, learning about mapM, foldlM, bind, ... we're big lightbulb moments for me while learning Haskell.

[rbasso]

Ok. I'll move it between hamming and space-age.
With #193 it's position will probably change, but we don't know when we will do that.

[petertseng]

As a final note:

A good starter exercise with Maybe would be great

What if we used hamming for the purpose? Note that it's only defined for equal-length strings. and https://github.com/exercism/x-common/blob/master/hamming.json says to test unequal length strings and expect an error, which could be a good time to use Maybe.

[rbasso]

What if we used hamming for the purpose?

Perfect, @petertseng. hamming should definitely return a Maybe. 😄

I'll add it to the list in #194 so we don't forget about it.