swift3新路程14数字表达进制

十进制、二进制、八进制、十六进制

A decimal number,with no prefix

A binary number,with a 0b prefix

An octal number,with a 0o prefix

A hexadecimal number,with a 0x prefix

Decimal floats can also have an optional exponent,indicated by an uppercase or lowercase e;

Hexadecimal floats must have an exponent,indicated by an uppercase or lowercase p.

十进制指数
For decimal numbers with an exponent of exp,the base number is multiplied by 10exp

1.25e2 means 1.25 x 102,or 125.0.
1.25e-2 means 1.25 x 10-2,or 0.0125.

十六进制指数

For hexadecimal numbers with an exponent of exp,the base number is multiplied by 2exp:

0xFp2 means 15 x 22,or 60.0.
0xFp-2 means 15 x 2-2,or 3.75.