Path/Stage 1 · Foundations

Constants & iota

Compile-time values and Go's auto-incrementing identifier.

Gopher narrator

Have the gopher read this explanation out loud.

Constants use const and are fixed at compile time. Inside a const (...) block, iota starts at 0 and increases by one per line — handy for enum-like values. It resets to 0 at the start of each new const block.

const Pi = 3.14159

const (
    Sunday = iota // 0
    Monday        // 1
    Tuesday       // 2
)

Exercise 1·code

Declare a Weekday type with an iota-based const block for Sunday..Saturday (Sunday = 0). Implement isWeekend(d Weekday) bool returning true for Saturday and Sunday only. A hidden test suite covers every day.

Plate · main.go

Test suite · go test

TestDayValuespending
TestIsWeekendWeekdayspending
TestIsWeekendWeekendpending

Hint

Inside the const block set the first line to Sunday Weekday = iota; the rest inherit the type and increment automatically.

Exercise 2·mcq

Inside a const block, iota resets to 0…