Mal implementation by Crystal

[rhysd]

I implemented all steps of Mal by Crystal.

I checked that my implementation passed all test cases and self-hosted Mal implementation also passed in my OS X environment.

[kanaka]

@rhysd something seems to be off with printing:

$ crystal run ./step1_read_print.cr
user> 123
#<Mal::Type:0x2094f90>

$ crystal run ./stepA_mal.cr 
#<Mal::Type:0x17c4640>#<Mal::Type:0x17cf140>#<Mal::Type:0x17d4000>#<Mal::Type:0x17da240>#<Mal::Type:0x17dbc00>Mal [crystal]
user> 123
#<Mal::Type:0x17db0c0>#<Mal::Type:0x17e2fc0>

I tested with crystal-0.7.2 on Ubuntu 14.04.1

[rhysd]

Sorry, previous deleted comments were my mistake. It seemed that I didn't notice the bug because of compiler's cache. I'll fix it.

[rhysd]

It seems that print() is added in Crystal 0.7.2 and Mal's print is not called. I'll use Mal module to avoid that.

[rhysd]

@kanaka

I fixed the bug then confirmed tests for step0 ~ stepA and self-hosted mal with Crystal 0.7.2.

[rhysd]

Thank you!
I really enjoyed implementing mal.

[kanaka]

@rhysd You're welcome! Do you have any feedback on the guide? Especially places where you got stuck that the guide could have helped address?

I did a couple of minor cleanups to the Makefile. I also pushed an update to the README to bump the language count (35 now!) and to list you as the creator of this implementation.

The only thing left is for you to tweet about it and I'll retweet :-)

[rhysd]

@kanaka

Sorry, I failed to catch your reply.

I did a couple of minor cleanups to the Makefile. I also pushed an update to the README to bump the language count (35 now!) and to list you as the creator of this implementation.

I see. Thank you for your work.

Do you have any feedback on the guide?

I think it is better to add more tests for object deepcopy.

Many languages (including Crystal) provide reference semantics, which employs shallow copy to copy array, dictionary and so on. It leads to shallow copy of mal's object and enables to change a value in environment from outside.
I met a bug that breaks environment in self-hosted mal and I worked a bit hard to fix it. Specifically, I forgot deepcopy for dictionary here. No test for previous steps couldn't find the shallow copy bug.

[kanaka]

@rhysd that's a good point. Do you have some example tests that would have caught the problem in your case?