7 ms·

TIL You can write javascript numbers with underscore separators https://v8.dev/features/numeric-separators https://v8.dev/features/numeric-separators

codetrotter 5y ago
Same in Python 3 and Rust too. https://www.python.org/dev/peps/pep-0515/ https://www.python.org/dev/peps/pep-0515/ https://doc.rust-lang.org/rust-by-example/primitives/literals.html https://doc.rust-lang.org/rust-by-example/primitives/literal...
- omegalulw 5y ago
  Interestingly, why do they specify base 10 integers as: nonzerodigit (["_"] digit)* | "0" (["_"] "0")* Isn't digit (["_"] "0")* simpler?
  - Jasper_ 5y ago
    012345 is the old way of doing octal notation in Python, which has its roots in C. I'm guessing they want to prevent ambiguity by making it so that it's an error for "012345" to be a decimal literal.
    - dr_zoidberg 5y ago
      Yes, it gives an error -- if you want decimals, you can't use leading 0's: Python 3.6.3 (v3.6.3:2c5fed8, Oct 3 2017, 18:11:49) [MSC v.1900 64 bit (AMD64)] Type 'copyright', 'credits' or 'license' for more information IPython 7.2.0 -- An enhanced Interactive Python. Type '?' for help. In [1]: 01 File "<ipython-input-1-3351d58b1d3b>", line 1 01 ^ SyntaxError: invalid token In [2]: 0o1 Out[2]: 1 In [3]: 0o10 Out[3]: 8
    - nicoburns 5y ago
      Not only that, octal notation is actually valid in non strict-mode versions of JavaScript (which is still the default unless you opt-in with "use strict"). So it would be backwards incompatible outside of strict mode, and very confusing if changing from non-strict to strict-mode changed the semantics without giving an error/warning.
    - tdeck 5y ago
      I always thought this was one of the worst notation conventions in modern languages.
      - Gibbon1 5y ago
        I've felt for 35 years they could do everyone a favor and break everything that dependens on a leading zero to represent octal.
- de6u99er 5y ago
  And Java since Java7 which was released in 2011.
  - nayuki 5y ago
    Note that different languages have slightly different syntax rules. 0_0: Legal in Java, legal in Python, illegal in JavaScript. 0__0: Legal in Java, illegal in Python, illegal in JavaScript. 0x_0: Illegal in Java, legal in Python, illegal in JavaScript. 0_, 0_.0, 0._0: Illegal in all three. It wouldn't surprise me if C# and C++(14) have differing edge cases too.
    - chrismorgan 5y ago
      0_0, 0__0, 0x_0, 0_ and 0_.0 are legal in Rust. 0._0 is the only one of those that’s illegal (“`{integer}` is a primitive type and therefore doesn't have fields”).
      - Zababa 5y ago
        To clarify the special case in Rust ( 0._0 ), it's due to te definition of identifiers: https://doc.bccnsoft.com/docs/rust-1.36.0-docs-html/reference/identifiers.html https://doc.bccnsoft.com/docs/rust-1.36.0-docs-html/referenc.... _0 is an identifier, as it's an underscore followed by one alphanumeric character. Thus, 0._0 means "the field _0 of 0". Since it's an identifier starting with _, you won't get any warnings if you don't use it. Small example: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=b91364d3e27acda95c094f8cedbb71a4 https://play.rust-lang.org/?version=stable&mode=debug&editio...
    - austinjp 5y ago
      O_o
  - scns 5y ago
    Interestin, i saw it first in Kotlin.
- banana_giraffe 5y ago
  And C# since 7.0 https://github.com/dotnet/csharplang/blob/main/proposals/csharp-7.0/digit-separators.md https://github.com/dotnet/csharplang/blob/main/proposals/csh... First time I saw it was in C#, I love it personally
  - pa7ch 5y ago
    And go since 1.13 https://golang.org/doc/go1.13#language https://golang.org/doc/go1.13#language
  - kevin_thibedeau 5y ago
    It is lifted from Ada. A language ahead of its time.
- thewakalix 5y ago
  And Haskell with the NumericUnderscores GHC extension. https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/numeric_underscores.html https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/nume...
deleted 5y ago
[deleted]
sarreph 5y ago
You can also write JavaScript numbers with E notation (i.e. multiplied by 10 to the power of x), which is basically what I do with all numbers above 1,000 or below 0.001 now. It has the rare benefit, for big / small numbers, of being both more readable and more concise. Example: 1e3 === 1000; 1e-3 === 0.001; 45.2e6 === 45200000;
magoghm 5y ago
And also in Ruby.
- petepete 5y ago
  I always thought Perl was the originator of this style, which would explain why it's been in Ruby forever. I wonder where it started if it existed before Perl.
  - pjmlp 5y ago
    Ada and ALGOL dialects.
jraph 5y ago
D has had this for quite some time, C++ now too (with quote characters instead of underscores)
lucb1e 5y ago
Since 2019 in the leading browsers (Firefox and Chromium); 2020 if you use something else like Edge or Samsung Internet; 2021 for Chrome or Firefox on mobile... and of course you can forget about MSIE or Opera Mobile support as usual. https://caniuse.com/mdn-javascript_grammar_numeric_separators https://caniuse.com/mdn-javascript_grammar_numeric_separator...

codetrotter 5y ago

Same in Python 3 and Rust too. https://www.python.org/dev/peps/pep-0515/ https://www.python.org/dev/peps/pep-0515/ https://doc.rust-lang.org/rust-by-example/primitives/literals.html https://doc.rust-lang.org/rust-by-example/primitives/literal...

omegalulw 5y ago
Interestingly, why do they specify base 10 integers as: nonzerodigit (["_"] digit)* | "0" (["_"] "0")* Isn't digit (["_"] "0")* simpler?
- Jasper_ 5y ago
  012345 is the old way of doing octal notation in Python, which has its roots in C. I'm guessing they want to prevent ambiguity by making it so that it's an error for "012345" to be a decimal literal.
  - dr_zoidberg 5y ago
    Yes, it gives an error -- if you want decimals, you can't use leading 0's: Python 3.6.3 (v3.6.3:2c5fed8, Oct 3 2017, 18:11:49) [MSC v.1900 64 bit (AMD64)] Type 'copyright', 'credits' or 'license' for more information IPython 7.2.0 -- An enhanced Interactive Python. Type '?' for help. In [1]: 01 File "<ipython-input-1-3351d58b1d3b>", line 1 01 ^ SyntaxError: invalid token In [2]: 0o1 Out[2]: 1 In [3]: 0o10 Out[3]: 8
  - nicoburns 5y ago
    Not only that, octal notation is actually valid in non strict-mode versions of JavaScript (which is still the default unless you opt-in with "use strict"). So it would be backwards incompatible outside of strict mode, and very confusing if changing from non-strict to strict-mode changed the semantics without giving an error/warning.
  - tdeck 5y ago
    I always thought this was one of the worst notation conventions in modern languages.
    - Gibbon1 5y ago
      I've felt for 35 years they could do everyone a favor and break everything that dependens on a leading zero to represent octal.
de6u99er 5y ago
And Java since Java7 which was released in 2011.
- nayuki 5y ago
  Note that different languages have slightly different syntax rules. 0_0: Legal in Java, legal in Python, illegal in JavaScript. 0__0: Legal in Java, illegal in Python, illegal in JavaScript. 0x_0: Illegal in Java, legal in Python, illegal in JavaScript. 0_, 0_.0, 0._0: Illegal in all three. It wouldn't surprise me if C# and C++(14) have differing edge cases too.
  - chrismorgan 5y ago
    0_0, 0__0, 0x_0, 0_ and 0_.0 are legal in Rust. 0._0 is the only one of those that’s illegal (“`{integer}` is a primitive type and therefore doesn't have fields”).
    - Zababa 5y ago
      To clarify the special case in Rust ( 0._0 ), it's due to te definition of identifiers: https://doc.bccnsoft.com/docs/rust-1.36.0-docs-html/reference/identifiers.html https://doc.bccnsoft.com/docs/rust-1.36.0-docs-html/referenc.... _0 is an identifier, as it's an underscore followed by one alphanumeric character. Thus, 0._0 means "the field _0 of 0". Since it's an identifier starting with _, you won't get any warnings if you don't use it. Small example: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=b91364d3e27acda95c094f8cedbb71a4 https://play.rust-lang.org/?version=stable&mode=debug&editio...
  - austinjp 5y ago
    O_o
- scns 5y ago
  Interestin, i saw it first in Kotlin.
banana_giraffe 5y ago
And C# since 7.0 https://github.com/dotnet/csharplang/blob/main/proposals/csharp-7.0/digit-separators.md https://github.com/dotnet/csharplang/blob/main/proposals/csh... First time I saw it was in C#, I love it personally
- pa7ch 5y ago
  And go since 1.13 https://golang.org/doc/go1.13#language https://golang.org/doc/go1.13#language
- kevin_thibedeau 5y ago
  It is lifted from Ada. A language ahead of its time.
thewakalix 5y ago
And Haskell with the NumericUnderscores GHC extension. https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/numeric_underscores.html https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/nume...

deleted 5y ago

[deleted]

sarreph 5y ago

You can also write JavaScript numbers with E notation (i.e. multiplied by 10 to the power of x), which is basically what I do with all numbers above 1,000 or below 0.001 now. It has the rare benefit, for big / small numbers, of being both more readable and more concise. Example: 1e3 === 1000; 1e-3 === 0.001; 45.2e6 === 45200000;

magoghm 5y ago

And also in Ruby.

petepete 5y ago
I always thought Perl was the originator of this style, which would explain why it's been in Ruby forever. I wonder where it started if it existed before Perl.
- pjmlp 5y ago
  Ada and ALGOL dialects.

jraph 5y ago

D has had this for quite some time, C++ now too (with quote characters instead of underscores)

lucb1e 5y ago

Since 2019 in the leading browsers (Firefox and Chromium); 2020 if you use something else like Edge or Samsung Internet; 2021 for Chrome or Firefox on mobile... and of course you can forget about MSIE or Opera Mobile support as usual. https://caniuse.com/mdn-javascript_grammar_numeric_separators https://caniuse.com/mdn-javascript_grammar_numeric_separator...