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In Ada it is possible to write numbers with underscores for separating digits, which greatly improves readability. For example: 1_000_000 (which is equivalent to 1000000) Is there some similar way for C++?
EDIT: This is question about source code, not I/O.
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%d stands for decimal and it expects an argument of type int (or some smaller signed integer type that then gets promoted). Floating-point types float and double both get passed the same way (promoted to double ) and both of them use %f .
"%f" is the (or at least one) correct format for a double. There is no format for a float , because if you attempt to pass a float to printf , it'll be promoted to double before printf receives it1.
We can print the double value using both %f and %lf format specifier because printf treats both float and double are same. So, we can use both %f and %lf to print a double value.
The first argument to printf is a string of identifiers. %s refers to a string %d refers to an integer %c refers to a character. Therefore: %s%d%s%c\n prints the string "The first character in sting ", %d prints i, %s prints " is ", and %c prints str[0]. Follow this answer to receive notifications.
As of C++14, you can use ' as a digit group separator:
auto one_m = 1'000'000;
Previous versions of C++ did not support this natively. There were two major workarounds:
Using user-defined literals in C++11; this would allow you to write code as follows:
auto x = "1_000_000"_i;
(Writing this as a constexpr would be trickier – but is definitely possible.)
Using a straightforward macro, which would allow the following code:
auto x = NUM(1,000,000);
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