Golang : automatically figure out array length(size) with three dots

In Go, you can specify a length(size) of an array either explicitly or implicitly(i.e let the compiler figure out) with the three dots [...] .

However, before we proceed further, it is good to know the tiny difference between array and slice.

Arrays length are fixed during run time. Slices are not bounded by their length and values from one slice can be passed to another even when their lengths are different.

These are ARRAYS

 // Explicit length. You specified it  
 var days := [7]string { "Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun" }

 // Implicit length with the three dots. (Compiler will determine the length)
 var days := [...]string { "Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun" } 

This is a SLICE

 var days := []string { "Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun" }

The three dots [...] can be useful in situation when you wanted to create an array based on content from files or streams, but do not know the length until run time.

Hope this simple tutorial can be useful to you.

By Adam Ng

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