Chapter 6. Functions
A function (also known as a procedure or a subroutine) is an independent section of code that maps zero or more input parameters to zero or more output parameters. As illustrated in Figure 6-1, functions are often represented as a black box.
![](/api/v2/epubs/9781491941997/files/assets/itpg_06in01.png)
Figure 6-1. A black box function
In previous chapters, the programs we have written in Go have used only one function:
func
main
()
{}
We will now begin writing programs that use more than one function.
Your Second Function
Let’s take another look at the following program from Chapter 5:
func
main
()
{
xs
:=
[]
float64
{
98
,
93
,
77
,
82
,
83
}
total
:=
0.0
for
_
,
v
:=
range
xs
{
total
+=
v
}
fmt
.
Println
(
total
/
float64
(
len
(
xs
)))
}
This program computes the average of a series of numbers. Finding the average like this is a very general problem, so it’s an ideal candidate for definition as a function.
The average
function will need to take in a slice of float64
s and return one float64
. Insert this before the main
function:
func
average
(
xs
[]
float64
)
float64
{
panic
(
"Not Implemented"
)
}
Functions start with the keyword func
, followed by the function’s name. The parameters (inputs) of the function are defined like this: name type, name type, …
. Our function has one parameter (the list of scores) that we named xs
. After the parameters, we put the return type. Collectively, the parameters and the return type are known as the function’s ...
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