Documentation for 0b (radix form) Number literals

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(Syntax) 0b (radix form) Number literals

Number literals are generally specified in base ten, unless a prefix like 0x (hexadecimal, base 16), 0o (octal, base 8) or 0b (binary, base 2) or an explicit base in adverbial notation like :16<A0> specifies it otherwise. Unlike other programming languages, leading zeros do not indicate base 8; instead a compile-time warning is issued.

In all literal formats, you can use underscores to group digits; they don't carry any semantic information; the following literals all evaluate to the same number:

1000000
1_000_000
10_00000
100_00_00

Int literals

Integers default to signed base-10, but you can use other bases. For details, see Int.

-2          # actually not a literal, but unary - operator applied to numeric literal 2 
12345
0xBEEF      # base 16 
0o755       # base 8 
:3<1201>    # arbitrary base, here base 3 

Rat literals

Rat literals (rationals) are very common, and take the place of decimals or floats in many other languages. Integer division also results in a Rat.

1.0
3.14159
-2.5        # Not actually a literal, but still a Rat 
:3<21.0012> # Base 3 rational 
2/3         # Not actually a literal, but still a Rat 

Num literals

Scientific notation with an integer exponent to base ten after an e produces floating point number:

1e0
6.022e23
1e-9
-2e48
2e2.5       # error 

Complex literals

Complex numbers are written either as an imaginary number (which is just a rational number with postfix i appended), or as a sum of a real and an imaginary number:

1+2i
6.123e5i    # note that this is 6.123e5 * i and not 6.123 * 10 ** (5i)