How to separate digits in numeric constants (i.e. 10,000) in C or C++ code

Question

Java allows the digits in a numeric constant to be separated as follows:

int a = 1_000_000;

Does C or C++ have a similar construct?

@Rakete1111, is this C++? in C I receive an error: `expected ‘,’ or ‘;’ before '\x303030'` — David Ranieri, Sep 09 '16 at 13:58
C is not C++ and vice versa, pick one because the answer will most likely differ. — Borgleader, Sep 09 '16 at 13:59
Thank you @Rakete1111, and whats the benefit of separate the number? — David Ranieri, Sep 09 '16 at 14:03
This is going to confuse the poor IDEs with syntax highlighting... — Eugene Sh., Sep 09 '16 at 14:03
@AlterMann Well, what's more readable: `unsigned long a = 12387461;` or `unsigned long a = 12'387'461;`? :) — Rakete1111, Sep 09 '16 at 14:04
@AlterMann Well, it can improve readability a bit. But as I said, if it will mess the syntax highlighting, it will just make it worse.. — Eugene Sh., Sep 09 '16 at 14:04
C programmers would write `0x000F4240`. Engineers would write `(int)1e6`. — Lundin, Sep 09 '16 at 14:21
Come to think of it, C programmers probably write it as `#define x(x, y, z) x ## y ## z` then `printf("%d", x(1,000,000));`...there's no problems that can't be fixed with icky macros (the duct tape of C programming). — Lundin, Sep 09 '16 at 14:32
@EugeneSh. `#define hex32(b3, b2, b1, b0) 0x ## b3 ## b2 ## b1 ## b0` then `hex32(00,0F,42,40)` :) — Lundin, Sep 09 '16 at 14:33
@Lundin Your `x4(10,000,000,000)` has an advantage over another way of breaking up wide constants. `10*1000*1000*1000` can overflow. IMO your alternate macro is worthy of an answer, but likely to attract to many nay-sayers. — chux - Reinstate Monica, Sep 09 '16 at 14:34
@Lundin Yeah, but my coworkers won't accept it gracefully, I think... — Eugene Sh., Sep 09 '16 at 14:35
@EugeneSh. Then consider replacing your co-workers with icky macros! — Lundin, Sep 09 '16 at 14:36
an alternative in C is `1000*1000*1000LL` http://stackoverflow.com/q/8488989/995714 — phuclv, Sep 09 '16 at 16:41
[Making large constants in C source more readable?](http://stackoverflow.com/q/10977260/995714), [Representing big numbers in source code for readability?](http://stackoverflow.com/q/14220217/995714) — phuclv, Sep 09 '16 at 16:47
@Lundin I'm surprised you don't have an account on [Programming Puzzles & Code Golf](http://codegolf.stackexchange.com/) with suggestions like these... — trichoplax is on Codidact now, Sep 09 '16 at 19:12

Arnav Borborah · Accepted Answer · 2016-09-09T14:06:36.137

The only way to do this is in C++14, is with single quotes, like this. Unfortunately, the only problem with this is that syntax highlighting often gets messed up with the notation below, and you can see that in my example as well:

int i = 1'000'000;

Working Example

According to http://en.cppreference.com/w/cpp/language/user_literal:

In the integer and floating-point digit sequences, optional separators ' are allowed between any two digits and are ignored (since C++14)

score 19 · Answer 2 · edited Sep 09 '16 at 18:12

19

You may write in C++ 14

int a = 1'000'000;

In C such a feature is absent.

edited Sep 09 '16 at 18:12

Arnav Borborah

11,357
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answered Sep 09 '16 at 13:57

Vlad from Moscow

301,070
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4

Maybe mention that OP has to use C++14? – Rakete1111 Sep 09 '16 at 13:57
@Rakete1111 I do not remember is it valid in C++ 11?:) – Vlad from Moscow Sep 09 '16 at 13:58
I think [this](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3781.pdf) is the proposal which was accepted, but I'm not sure. It's not valid C++11. – Rakete1111 Sep 09 '16 at 14:00

How to separate digits in numeric constants (i.e. 10,000) in C or C++ code

2 Answers2