✌️ 🔪 🐠 20_20 is the year in which underscore in numeric literals won 🚕 👨🏿‍💼 🚣🏽

Suddenly you didn't know, but in the language you write in, you can use _in numbers. For example, the following PHP code:

<?php

print(1_00);
print(100);

Will output 100100( check online ). This syntactic sugar appeared in Ada in 1980 and has had mixed success over the past 40 years. But over the past year, it has been added to javascript, PHP, Go, Scala, and even conservative Erlang. I cannot explain what caused the surge in popularity, so in this article I will simply describe the history of separators in numbers.

19 68 Algol

At the dawn of programming, we didn't really bother with spaces, and therefore in Algol it was possible to insert a space in variable names and numbers. For example, a 1 st varis a valid variable name, and a synonym a1stvar. The code:

BEGIN
    INT  a 1 st var = 1 234 567;
    REAL a 2 nd var  = 3      .    1 4159 26 5 359;
    print((a1stvar, newline, a2ndvar))
END

Will output ( check ):

   +1234567
+3.14159265359000e  +0

, , Algol. , , FORTRAN 77 .

UPD: ( fixed-form source files). fixed-form source files 2018 .

19_80 Ada

, 1980 Ada. , Ada 2 16. 11 (6 ) 5#11#. , , I: Float := 3#0.1# — 1/3 ( ):

with Ada.Float_Text_IO; use Ada.Float_Text_IO;
procedure hello is
    I: Float := 3#0.1#;
    J: Float := 1_00.0;
begin
    Put(I);
    Put(J);
end hello;

3.33333E-01 1.00000E+02 ().

19_85 Caml

19_87 Perl

, , Caml Perl. Perl , ( ) :

$x = 1_0_0;
$y = 2__5________0;
$z = $x+$y;

print "Sum of $x + $y = $z";

Sum of 100 + 250 = 350 ().

19_93 Ruby

19_96 OCaml

, , . OCaml () Caml, Ruby Perl, (, ).

20_03 D (v0.69)

D , , ( ).

20_10 Rust

20_11 Java (SE 7)

20_12 Julia

Rust OCaml, Julia Ruby. Java Perl .

20_14 Swift

Rust.

20'14 C++ (v14)

. , C++ . , _1 . :

#include <iostream>

int main()
{
  for (int _1 = 0; _1 < 5; ++_1) {
    std::cout << _1 << " ";
  }
}

0 1 2 3 4 (). C++ 1'00.

UPD: , (User-defined literals). 1:

#include <iostream>

constexpr unsigned long long operator"" _0(unsigned long long i)
{
    return 1;
}

int main()
{
    int x = 0_0;
    std::cout << x;

    return 0;
}

20_16 Python (3.6)

20_17 C# (7.0), Kotlin (v1.1)

20_18 Haskell (GHC 8.6.1)

20_19 JS (V8 v7.5, Chrome 75), PHP (v7.4), Go (v1.13), Scala (v2.13)

- , . , , . , PHP :

// PHP 7.3
decimal : [1–9][0–9]* | 0
hexadecimal : 0[xX][0–9a–fA–F]+
octal : 0[0–7]+
binary : 0[bB][01]+

// PHP 7.4
decimal : [1–9][0–9]*(_[0–9]+)* | 0
hexadecimal : 0[xX][0–9a–fA–F]+(_[0–9a–fA–F]+)*
octal : 0[0–7]+(_[0–7]+)*
binary : 0[bB][01]+(_[01]+)*

, PHP :

20_20 Erlang (v23)

Erlang. , , Erlang , Ada ( ), ( 36). , () 3z 36 (=143).

-module(main).
-export([start/0]).

start() ->
  io:fwrite("~w", [36#3z]).

33 .

20_20 is the year in which underscore in numeric literals won