Issue #17773 has been updated by sawa (Tsuyoshi Sawada).


jeremyevans0 (Jeremy Evans) wrote in #note-2:
> If you are checking for user input, aliasing `zero?` to `empty?` seems wrong, as `0` is a valid non-empty user input.

I do not understand what you exactly mean by 0 is valid. But presumably, if 0 is valid in whatever sense you have in mind, then empty string is valid as well in the same sense. On the other hand, in some contexts, 0 is not valid, say, for a transfer amount in a bank transfer page, just as an empty string is not valid, say, in a required user's name field in a registration form.

On top of that, in the first place, the distinction in question is not valid vs. invalid. That is irrelevant. It is about explicit input vs. default. 

> [I}f you care whether a user input was empty, you should check whether a user input string is empty before converting it to a number, instead of after.

As for numeric fields, I am discussing cases where the default is `0` and the user input (via `to_i`, perhaps) returned `0`. Empty string is irrelevant here.

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Feature #17773: Alias `Numeric#zero?` and `Float#zero?` as `Numeric#empty?` and `Float#empty?`
https://bugs.ruby-lang.org/issues/17773#change-91239

* Author: sawa (Tsuyoshi Sawada)
* Status: Open
* Priority: Normal
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When dealing with user input fields as in web applications, there are typical values that we want to consider as the default and/or absence of user input. For string/text inputs, list items, and attributes, we have `String#empty?`, `Array#empty?`, and `Hash#empty?` respectively, which seem to correspond to those cases. As for numerics, there are `Numeric#zero?` and `Float#zero?`.

However, there is no single term that covers all these cases. In a routine to check through the fields whether there is user input, we have to selectively use `empty?` or `zero?` depending on the type of the input field.

Many programming languages other than Ruby typically consider these values as falsy with respect to logical calculation. Ruby handles only `nil` and `false` as falsy, and that has clear advantages in many aspects, but with the cost of losing a simple way to handle these default values.

I propose to alias `Numeric#zero?` as `Numeric#empty?` and `Float#zero?` as `Float#empty?` so that we can simply use `empty?`. At first, calling zero as empty might sound strange, but at least for non-negative integers, set theoretic definitions usually define zero as the empty set, so it is not that strange after all.


Ruby on Rails' `blank?` is conceptually similar to this, but `0.blank?` returns `false`, so it is a different concept.



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