Basic variable types
- bool
- signed integer: int int8 int16 int 32 int64
- unsigned integer: unint unit8 unit16 unit32 unit64 unitptr
- byte (alias for uint8)
- run (unicode point, alias for int32)
- float32 float64
- complex64 complex128
integer comparison
| Type | Description |
|---|---|
| int unit uintptr | at least 32 bit based on OS (32 bit on 32 bit OS, 64 bit on 64 bit OS |
| int8 |
-128 ~ 127 ($ -2^7$ ~ $2^7-1$) |
| unit8 |
0 ~ 255 (0 ~ $2^8-1$) |
| int16 | -32768 ~ 32767 |
| unit16 | 0 ~ 65535 |
(if there is no any special reason, int should be used when we need a number)
- byte = unit8 (these types are to differentiate byte and number)
Get the biggest number of a type
| Type | Go syntax | Meaning |
|---|---|---|
| unint64 | 1<<64 - 1 | 2^64 - 1 |
| unint8 | 1<<8 - 1 | 2^8 - 1 = 255 |
How it works?
big = 1 << 100 // shift a 1 bit left 100 places <=> 2^100
small = big >> 99 // it right again 99 places <=> 2^-99, so we end up with 1<<1, or 2
Type conversion
var i int = 42
var f float = float64(i)
var u int = unint(f)
// same as
i := 42
f := float64(i)
u := uint(f)
init() function
- init() is called after package variable declaration
- each package may have multiple init()
- order of calling init() (in case of multiple init) is un-guaranteed
main() function
main() is called after all init() are run