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Comment by MaxBarraclough | Hacker News Reader

> I wouldn't bat an eyelid to discover that `/` had type `int -> int -> float`

I'd bat both eyelids, that's the kind of surprising design decision that would turn me away from a language. To my knowledge, no major programming language does this, and there's wisdom in the principle of least surprise.

edit: I am of course mistaken, Python does exactly this. Corrected by chrisseaton again!

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> I'd bat both eyelids, that's the kind of surprising design decision that would turn me away from a language. To my knowledge, no major programming language does this, and there's wisdom in the principle of least surprise.

Lol prepare to bat your eyelids.

    % python
    Python 3.8.5 (default, Jul 21 2020, 10:48:26) 
    [Clang 11.0.3 (clang-1103.0.32.62)] on darwin
    Type "help", "copyright", "credits" or "license" for more information.
    >>> 1 / 2
    0.5

I'll bat my eyelids, but only after I kick myself ;-P

If you're up for a game of No True Scotsman, can you name me a statically typed language that does the same?

Visual basic

I don't think so. According to this, in Visual Basic, the '/' operator isn't defined for integer types.

https://docs.microsoft.com/en-us/dotnet/visual-basic/languag...

Integers are right there in the table on the page you're linking to.

If you don't believe me, perhaps you'll believe output from the machine.

https://tio.run/##K0vSTc4vSv3/3zc/pTQnVcEjNScnn4szuDRJwTcxM0...

* edited for guideline compliance

Looks like you're right. In my defense the page I linked states that The / operator is defined only for the Decimal, Single, and Double data types. I suppose it accepts integer types by means of 'widening'?

> Did you read it?

The HN guidelines ask that you don't do that.

I've edited my comment for guideline compliance.

I don't think it settles anything, but a trivial function that divides two integers and returns the result compiles to this:

  IL_0000:  ldarg.1     
  IL_0001:  conv.r8     
  IL_0002:  ldarg.2     
  IL_0003:  conv.r8     
  IL_0004:  div         
  IL_0005:  ret

conv.r8 is an explicit conversion to double precision float in the target language, MSIL.

I was already convinced by your earlier tio.run example, but I'm still a bit baffled by the page saying The / operator is defined only for the Decimal, Single, and Double data types.

Nim https://play.nim-lang.org/#ix=2zbk

Interesting, thanks. I see Nim uses '/%' for integer division. [0] I can't say I like that decision.

[0] https://nim-lang.org/docs/manual.html#types-preminusdefined-...

Unsigned integer division. In practice I haven’t seen this operator used anywhere yet.

Have I gone mad? (EDIT: it appears I have.)

```

GHCi, version 8.6.5: http://www.haskell.org/ghc/ :? for help

Prelude> 1 / 2

0.5

```

This is because 1 and 2 are polymorphic and get instantiated to floats here. Witchcraft.

I think you're still right though. I know Haskell has an unusual approach to numbers, but it looks like the resultant type is indeed different from the type of the operands. I got this from typeOf (/):

    Note: there are several potential instances:
    instance RealFloat a => Fractional (Complex a)
    -- Defined in ‘Data.Complex’
    instance HasResolution a => Fractional (Data.Fixed.Fixed a)
    -- Defined in ‘Data.Fixed’
    instance Integral a => Fractional (Ratio a)
    -- Defined in ‘GHC.Real’
    ...plus two others

There are many instances for Fractional, but the resultant type of the (/) operator is always the same as the operands:

    GHCI> :i (/)
    class Num a => Fractional a where
      (/) :: a -> a -> a
      ...
            -- Defined in ‘GHC.Real’
    infixl 7 /

The key is that integer types aren't Fractional, so the Haskell 2010 defaulting rules[1] cause the literals to be interpreted as Double. With an appropriate default declaration GHC could have picked Ratio Integer, Complex Double, etc. instead, but without one Integer and Double are the only options and Integer wouldn't satisfy the constraints.

[1] https://www.haskell.org/onlinereport/haskell2010/haskellch4....

Julia? There's an integer division operator, but the default is... More complex:

https://docs.julialang.org/en/v1/manual/integers-and-floatin...

Python2 did it the other way, wasnt it?

(/ 1 2) #=> 1/2 Clojure as well, though it's a rational not a float.

Interesting, thanks

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