Make #pretty_print actually pretty

[agarie]

I'm trying to come up with some examples of how to use NMatrix and, obviously, #pretty_print/#pp is used lots of times.

I wanted to throw this discussion to see how you guys think NMatrix/NVector should be printed. Any ideas? I'll try to come up with something and implement it, but I don't want to make this kind of change without listening to others.

[translunar]

I cleaned up the code in a recent commit. Have you tried it with pry (which uses coderay)? It looks a little better.

[agarie]

Some experiments in IRB:

> n = NMatrix.random(4)
> n.pp
[[0.6299860224178115, 0.2626926192712231, 0.9008651790526774, 0.7025077672785742]
[0.6629325603072921, 0.657471929860773, 0.9601643345978037, 0.7900181731280271]
[0.22735456931808107, 0.5035327724154458, 0.6728627567703459, 0.9629883418502257]
[0.36004767980910257, 0.6542623614657115, 0.9829866207607914, 0.6299860224178115]]
 => nil 

> u = NVector.random(3)
> u.pretty_print
[0.6652767626356697
0.1188537203789306
0.8368488043457466]
 => nil
> u.pp
 => "#<NVector:0x007fad838f6668 orientation:column shape:[3,1] dtype:float64 stype:dense>" 

The result from pretty_print is correct and acceptable, but obviously pp is wrong. This is probably due to it being an alias to NMatrix#pretty_print; as NVectors have dimension 1, it calls inspect directly. Just aliasing it again in NVector solves the problem:

> class NVector
>   alias :pp :pretty_print
> end
 => nil 
> u.pp
[0.6652767626356697
0.1188537203789306
0.8368488043457466]
 => nil 

I can send a PR with this. But there's one more question: why isn't there a to_s method defined? We could simply use puts in this case. Also, what about displaying it such that the indices appear next to the values? Like:

> n = NMatrix.seq(3)
> u = NVector.random(3)
> puts n
     0   1   2
0   0   1   2
1   3   4   5
2   6   7   8
> puts u
0   0.6652767626356697
1   0.1188537203789306
2   0.8368488043457466

I think this can be useful. If you agree with me, I can implement it during the weekend.

[translunar]

I don't think to_s should produce multi-line output. I haven't seen any others that do.

[agarie]

Why not? I agree that I've never seen others do that, but in this case it's much better (and useful) than #<NMatrix:0x007fff418a3b38>. Besides, if someone unfamiliar with Ruby (e.g. a scientist trying to use SciRuby tools for his work) wants to see how the operations work in IRB, he might not know the pp library or that NMatrix has the pp method.

In any case, I'll ask other Rubyists' opinions on this :)

[translunar]

Why not? Again, mainly because I haven't seen any other objects that do multiline to_s output (unless with assistance from pry).

[v0dro]

Can we try something like awesome_print?

[translunar]

No. I think we don't want to complicate NMatrix with additional dependencies, if possible.