From: shyouhei@...
Date: 2017-01-24T05:26:22+00:00
Subject: [ruby-core:79232] [Ruby trunk Bug#13152] Numeric parsing differences between ruby <-> crystal

Issue #13152 has been updated by Shyouhei Urabe.


Martin D��rst wrote:
> - What do other languages (in particular languages more well known that Cristal) do?

Here we go:

```sh
zsh % /bin/sh
sh-3.2$ echo $((-2 ** 4))
16
sh-3.2$
```

```perl
zsh % perl -e 'warn(eval("-2 ** 4"));'
-16 at -e line 1.
```

```php
zsh % php -a
Interactive shell

php > $a = -2 ** 4; echo $a;
-16
php >
```

```python
zsh % python3
Python 3.6.0 (default, Dec 24 2016, 00:01:50)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.42.1)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> -2 ** 4
-16
>>>
```

```julia
zsh % /Users/urabe.shyouhei/Applications/Julia-0.5.app/Contents/Resources/julia/bin/julia
               _
   _       _ _(_)_     |  A fresh approach to technical computing
  (_)     | (_) (_)    |  Documentation: http://docs.julialang.org
   _ _   _| |_  __ _   |  Type "?help" for help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 0.5.0 (2016-09-19 18:14 UTC)
 _/ |\__'_|_|_|\__'_|  |  Official http://julialang.org/ release
|__/                   |  x86_64-apple-darwin13.4.0

julia> -2 ** 4
ERROR: syntax: use "^" instead of "**"

julia> -2 ^ 4
-16

julia>
```

```haskell
zsh % ghci
GHCi, version 8.0.2: http://www.haskell.org/ghc/  :? for help
Prelude> -2 ** 4
-16.0
Prelude>
```

```ml
zsh % ocaml
        OCaml version 4.04.0

# -2 ** 4 ;;
Error: This expression has type int but an expression was expected of type
         float
# -2. ** 4. ;;
- : float = 16.
#
```

I also checked other languages like C#, Swift, Go, Rust and turned out they don't have this kind of operator.

So from my experiment I cannot say if it's Ruby or Cristal who's wrong.  I think it's a design choice.

----------------------------------------
Bug #13152: Numeric parsing differences between ruby <-> crystal
https://bugs.ruby-lang.org/issues/13152#change-62650

* Author: Jabari Zakiya
* Status: Rejected
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 
* Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN
----------------------------------------
I noticed this difference between ruby and crystal when converting a gem.

```ruby
puts   -2**4 -> -16 (ruby) || 16 (crystal)
puts (-2)**4 ->  16 (both)
```

ruby parses `-2**4` as `-(2**4)`, while crystal does `(-2)**4`, which is more intuitive.
This creates need to be careful converting negative number usage from ruby <-> crystal.
(I haven't investigated differences with other languages.)
Using parentheses to explicitly create intended outcomes can overcome this.

However, on the heels of the discussion/decision to not change the default rounding behavior of numerics
in 2.4.0 would it also be worth it to change this parsing behavior to make this more natural
and intuitive, as in crystal?



-- 
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