4.2. Underscores in numbers
Viper also supports underscores in numbers. A single underscore
can be used between digits, or between the radix prefix of
an integer and the rest of the digits, or, just before the E or e
in a floating point literal. Two underscores in a row are not
permitted. Underscores cannot go at the start or end of a number,
or next to the decimal point. Underscores cannot be used in the exponent.
Check this!
Examples:
0b_11111111 0B111_11111
0o_777 0O777
0d_999 0D999
0x_fFf 0xFFf
0_777 # DECIMAL (no warning required: viper mode only)
12_345.657_22_E7
The warning is issued, even for 0_777, because python mode
also allows underscores in numbers.