Numbers and Strings

Almost every program works with numbers, text, or both. Go gives each its own types, and it is picky about keeping them separate, which saves you from a whole family of sneaky bugs.

Two number types to start with

• int holds whole numbers: -3, 0, 42
• float64 holds numbers with a decimal point: 3.14, -0.5

The usual math operators work on both:

fmt.Println(8 + 3)
fmt.Println(8 - 3)
fmt.Println(8 * 3)
fmt.Println(8 / 3)
fmt.Println(8 % 3)

Those print 11, 5, 24, 2, and 2. Wait, why does 8 / 3 print 2 and not 2.66? Because both numbers are ints, Go does whole number division and throws away the remainder. The % operator gives you that remainder: 8 divided by 3 is 2, remainder 2.

fmt.Println(8.0 / 3.0)

With float64 values, division keeps the decimals and prints 2.6666666666666665.

Mixing types needs a conversion

Go will not silently mix an int with a float64. You convert one of them on purpose:

slices := 8
people := 3
each := float64(slices) / float64(people)
fmt.Println(each)

float64(slices) makes a float copy of the int. Explicit conversions feel wordy at first, but they mean you always know exactly what your numbers are doing.

Strings

A string is text inside double quotes. You can glue strings together with + and measure them with len:

first := "Grace"
last := "Hopper"
full := first + " " + last
fmt.Println(full)
fmt.Println(len(full))

That prints Grace Hopper and then 12, counting the space too.