Variables and Constants

Go has three ways to introduce a name, and they are not interchangeable.

• const fixes a value at compile time. It can never be reassigned, and it costs nothing at run time.
• var declares a variable, with or without an initial value. Without one it gets that type's zero value.
• := declares and assigns in one step, inferring the type. It only works inside a function.

Package-level names must use const or var; := is function-only.

Task

Open main.go and finish three things.

1. AppName is a constant string. Give it the value "Gofinity".
2. MaxRetries is a constant integer. Give it the value 3.
3. Implement RetryStatus(used int) string and Remaining(used int) int.

RetryStatus returns one sentence, built from the two constants:

Gofinity: 2 of 3 retries used, 1 remaining

Remaining returns just the number of retries left.

The rules:

• A negative used counts as 0. RetryStatus(-4) reports 0 of 3 ... 3 remaining.
• A used above MaxRetries counts as MaxRetries. The sentence must never claim more retries than exist, and Remaining must never go below 0.
• Both functions read MaxRetries rather than a hard-coded 3. Change the constant and every answer should move with it.

Hints

• const AppName = "Gofinity" is an untyped constant. It has no type until it is used, so it slots into anything a string fits, and MaxRetries slots into anything an integer fits. That is why you rarely need to write const MaxRetries int = 3, though you may.

• Clamping reads well as a small unexported helper both functions call:

  func clamp(used int) int {
  	if used < 0 {
  		return 0
  	}
  	...
  }
  

  Lowercase means package-private, which is right for something no caller outside this file needs.

• Inside a function, spent := clamp(used) is the idiomatic declaration. Save var for when you want the zero value or need the type spelled out.

• fmt.Sprintf("%s: %d of %d ...", AppName, spent, MaxRetries, left) builds the sentence. Count your verbs and your arguments: a mismatch shows up as %!d(MISSING) in the output rather than as a compile error.