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Ruby wrapper for parser #60

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Ruby wrapper for parser #60

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rajithv
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@rajithv rajithv commented Jul 8, 2016

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@isuruf
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isuruf commented Jul 8, 2016

Can you add some tests?

subject { SymEngine::parse('123 + 321') }

it { is_expected.to be_a SymEngine::Integer }
it { is_expected.to eq 444 }
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What will be if there's erroneous/unparseable input? (And, BTW, what input, if any is considered erroneous or unparseable by symengine?)

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@zverok I did think about that. In C++ code it will throw errors for unparseable code. Checking that may almost be equivalent to doing the parsing. There are 4 errors,

  1. Expected token!
  2. Invalid symbol or number!
  3. Mismatching parantheses!
  4. Operator inconsistency!

Catching the exceptions from the C++ code and throwing ruby exceptions will be covered in the weeks 9 and 10. So this issue will be solved then.

As of now, I wanted the tests to merely confirm that the Ruby wrapper is communicating successfully with the cwrapper. Actually the same idea was behind the matrix wrapper tests.

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Got it. I just always became suspicious when I see tests for success and not tests for fail :)
In fact, I always prefer to add empty contexts for such a deferred tests pathes, like this:

context "When there is parsing error" do
  # TODO: will be covered on weeks 9-10
end

Though, I'm not insisting, currently.

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That's a quite nice way to make it clear!

I'll keep this as it is, because week 9 is just one week away from now, probably I will start working on it even earlier.

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rajithv commented Jul 31, 2016

@isuruf can we merge this now, that the symengine/symengine#1044 has ParseError, so exception catching regarding Parser can be done in #63 with other exceptions?

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isuruf commented Aug 21, 2016

Can you resolve conflicts and add tests for parser errors?

@@ -18,5 +18,16 @@
it { is_expected.to be_a SymEngine::Rational }
its(:to_s) { is_expected.to eq '1/3' }
end

describe 'parse' do
subject { SymEngine::parse('123 + 321') }
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Since these specs act as documentation, can you add more strings for parsing?
eg.

  • x + (y * 3 - 5)
  • x ** y + f(x)
  • sin(x) + cos(y) / 2
  • 1 / 2 + 3 / 2
  • 1 + 2 * 2
  • tan(0) - sqrt(2)

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I would like to add a few more to this list

  • 5+-3
  • 5--3

All Without spaces
And

  • 5++3 or something like this to raise an error.

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rajithv commented Aug 22, 2016

@isuruf @abinashmeher999 please review.

end

it 'gives parse errors' do
expect { SymEngine::parse('12a + n34a9') }.to raise_error(RuntimeError)
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IMO the error message should be checked too since we don't have specific exception for ParseError.

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Why not to add ParseError as a specific exception? That seems worthwhile.

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Found just the thing that explains creating custom exceptions from Ruby C API: http://clalance.blogspot.in/2011/01/writing-ruby-extensions-in-c-part-5.html

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You don't have to create new exceptions.

  • SYMENGINE_RUNTIME_ERROR - rb_eRuntimeError
  • SYMENGINE_DIV_BY_ZERO - rb_eZeroDivError
  • SYMENGINE_NOT_IMPLEMENTED - rb_eNotImpError
  • SYMENGINE_PARSE_ERROR - rb_eSyntaxError
  • SYMENGINE_UNDEFINED - rb_eFloatDomainError ?? (I'm not sure what SYMENGINE_UNDEFINED is. Is this supposed to be a Domain error?)

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I partially agree to the above. While RuntimeError and ZeroDivisionError should be used, our code atleast shouldn't raise NotImplementedError and SyntaxError. The latter ones are ScriptErrors and not StandardErrors.
This post explains why it would be abuse of NotImplementedError. SyntaxError is not a right fit since it is raised while encountering invalid Ruby code. If the user wants to handle a parse error, (s)he will have to handle SyntaxError and that would also lead to unwanted silencing of the actual syntax error in the source code.

Also there is the technical problem that a rescue clause by default only catches the StandardErrors. It is highly advised that custom application level exceptions be derived from StandardError.

For SYMENGINE_UNDEFINED it can be just StandardError.

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@isuruf isuruf Aug 24, 2016

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I just checked SciRuby/nmatrix repo and they use NotImplementedError and IOError (instead of SyntaxError)

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rajithv commented Aug 24, 2016

@certik @abinashmeher999 @isuruf should I make another PR to continue this work after the GSoC period? Because the submission guidelines asked not to change the submitted material after submission. Pls advice on this.

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I assume the submission guidelines mention about putting in the exact amount of work that was achieved during the GSoC period. That you have mentioned in the blog post already. As long as you are not changing the contents and the amount of work achieved, you won't be violating any rules. Correct me If I am wrong.

You can keep the new exception making part for another PR. I think we can go ahead with merging this. Just a few more changes that have been suggested and we will be good to go.

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isuruf commented Oct 8, 2016

@rajithv, do you have time to finish this PR? If not, can you enable edits from maintainers?

@isuruf isuruf added this to the Release 0.1.0 milestone Oct 8, 2016
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certik commented Oct 11, 2016

@rajithv ping.

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rajithv commented Oct 12, 2016

@isuruf @certik I will find sometime to complete this PR

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5 participants