implement mod resource (% operator)

[czerwinskilukasz1]

If we have division and multiplication operators, we should also have a modulo operator. However, currently it does not exist.

🦄 40/6
float ask(call(get('/'),40,6))
6.666666666666667
🦄 40*6
int ask(call(get('*'),40,6))
240
🦄 .editor
// Entering editor mode (^D to finish, ^C to cancel)
40%6

Uncaught Error: Unknown identifier '%'!
    at Object.<anonymous> (/Users/milimetr/Desktop/x/askql/dist/askvm/lib/run.js:70:15)
    at Generator.next (<anonymous>)
    at /Users/milimetr/Desktop/x/askql/dist/askvm/lib/run.js:8:71
    at new Promise (<anonymous>)
    at __awaiter (/Users/milimetr/Desktop/x/askql/dist/askvm/lib/run.js:4:12)
    at Object.run (/Users/milimetr/Desktop/x/askql/dist/askvm/lib/run.js:29:12)
🦄

This task is to create a mod resource and a % operator linked to this resource.

--

Dear new contributor,

If you have any questions on how to start, please write a comment with a tag: @czerwinskilukasz1 or @mhagmajer, or join our Discord Community and let us know there. We will be very happy to help you start! :)
Hint for starters: As a starting point, take a look at src/askvm/resources/math/index.ts file, where a * operator and times resource are already linked or a couple of other ones and use them as an example.

Cheers,
Łukasz (@czerwinskilukasz1)
AskQL Core Developer

[mhagmajer]

Are we sure that we want to add an operator for modulo? We could just have mod function or a mod b expression. I'm asking because % already has meaning associated to it by math.

[czerwinskilukasz1]

As for %, I'd mimic Javascript to be honest.

a mod b expression looks good, how about we allow to write: a <funName> b for any function name ?
So that people could write also: 'a' concat 'b' or 1 plus 3? It looks to me like Scala and I like it.

[mhagmajer]

@czerwinskilukasz1 we actually already have a:concat(b) and do what you described for operators. Let's maybe keep one way of doing things so people don't need to make choice when writing AskScript programs.

[czerwinskilukasz1]

@mhagmajer , so I wouldn't introduce a new syntax a mod b for just one operation.

[mhagmajer]

@czerwinskilukasz1 sure, that would make AskScript easier for mathematicians which I think is an advantage.

So how about using % for percentage? I don't have strong opinion on this, however, just the fact that JavaScript uses this for modulo is not a sufficient argument for me here

[mhagmajer]

@czerwinskilukasz1 also how about a div b so integer division?

[czerwinskilukasz1]

@czerwinskilukasz1 sure, that would make AskScript easier for mathematicians which I think is an advantage.

So how about using % for percentage? I don't have strong opinion on this, however, just the fact that JavaScript uses this for modulo is not a sufficient argument for me here

I can't think of a better operator. Also, at least 20 other programming languages, including C/C++, C#, Java, Python, PHP and Kotlin, are using % for modulo.

As for percent, I'm totally not sure how we could use it.

@czerwinskilukasz1 also how about a div b so integer division?

So for what class of operations you would use this syntax?

[mhagmajer]

@czerwinskilukasz1

7 = ((7 div 3) * 3) + (7 mod 3)

About % we could say

let price = 1000 * 20%

I guess this would only make sense as a unary operator so the binary can be used for module. Would it be possible for the parser to support both?

[czerwinskilukasz1]

@czerwinskilukasz1

7 = ((7 div 3) * 3) + (7 mod 3)

I see, I see. Looks pretty good.
So, would we just hardcode it into AskScript grammar for just div and mod or rather for all identifiers?

About % we could say

let price = 1000 * 20%

I'm not convinced to this.

[mhagmajer]

@czerwinskilukasz1 let's do it in parser only for operators, div and mod and carry the discussion about unary % on a separate issue

[czerwinskilukasz1]

%: #264

[czerwinskilukasz1]

As for a mod b and a div b syntax, I moved it to issue #411

[czerwinskilukasz1]

@develper , following your comment, this issue is yours :)
If you had any questions, just tag me here.

[bhargav-khalasi]

@czerwinskilukasz1 , I have implemented the mod resource and want to know should I write tests for the same? If yes, then which test cases I should include.

[czerwinskilukasz1]

@czerwinskilukasz1 , I have implemented the mod resource and want to know should I write tests for the same? If yes, then which test cases I should include.

Great.

Let's add an example of <int> % <int> whose result should be 0, an example of <int> % <int> whose result should be non-zero, an example of <float> % <int> and <float> % <float>.
The same tests should be written twice for AskScript - once for mod() resource and once for % operator.
See src/askscript/__tests__/09-operators/operators-09-logicalOr-oper.test.ts and src/askscript/__tests__/09-operators/operators-09-logicalOr-res.test.ts for an example of such tests.