[ruby-core:83198] [Ruby trunk Feature#13693] Allow String#to_i and / or Kernel::Integer to parse e-notation

Issue #13693 has been updated by sos4nt (Stefan Schテシテ殕er).


> We also wondered whether you have an actual use case.

I stumbled across this behavior when playing with a simple calculator which collects user input via:

```ruby
number = Integer(gets)
```

> Exponential notation is usually used to express very large numbers or very small numbers that don't fit integer.

I'd remove the _"that don't fit integer"_ part, but yes, it's a way to enter and display very large (or very small) numbers more concise. That's exactly was I was attempting: entering `1e30`, so I don't have to type `1000000000000000000000000000000`.

> Consistency is important, but we don't add something just for 'consistency's sake.

The documentation for [`Kernel#Integer`](http://ruby-doc.org/core-2.4.2/Kernel.html#method-i-Integer) explains that _"[...] strings should be strictly conformed to numeric representation"_. Shouldn't it in turn be able to parse for example `"1e30"`, given that `1e30` _is_ a valid [numeric representation](http://ruby-doc.org/core-2.4.2/doc/syntax/literals_rdoc.html#label-Numbers)?

I think it's more a matter of completeness than consistency. It seems odd that `Integer()` happily parses `'0xff'`, `'0b100110'` and `'0740'` but cannot handle `'1e30'`.

----------------------------------------
Feature #13693: Allow String#to_i and / or Kernel::Integer to parse e-notation
https://bugs.ruby-lang.org/issues/13693#change-67142

* Author: sos4nt (Stefan Schテシテ殕er)
* Status: Rejected
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
`Kernel` can properly convert e-notation strings into numeric objects:

```ruby
     Float('1e+3') #=> 1000.0
  Rational('1e+3') #=> (1000/1)
   Complex('1e+3') #=> (1000.0+0i)
BigDecimal('1e+3') #=> 0.1e4
```

Same for `String`:

```ruby
'1e+3'.to_f #=> 1000.0
'1e+3'.to_r #=> (1000/1)
'1e+3'.to_c #=> (1000.0+0i)
'1e+3'.to_d #=> 0.1e4
```

With one exception:

```ruby
Integer('1e+3') #=> ArgumentError: invalid value for Integer(): "1e+3"
'1e+3'.to_i     #=> 1
```

Ruby should be able to convert e-notation strings to integers, too.



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