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Write Professional Command-line Programs in Go

Building the Application on Top of the Skeleton

Explore building a command-line calculator in Go by integrating arithmetic functions into a Cobra-based skeleton. Learn to handle command arguments and implement overflow checks for reliable addition and subtraction commands.

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Building your application on top of the skeleton

We will use the same code from the previous lesson and just bolt it on the new skeleton. If you want to follow along, you can use the terminal at the bottom of the lesson. First, let’s add the calc package to pkg/calc/calc.go:

package calc

const (
	maxUint=^uint(0)
	maxInt = int(maxUint >> 1)
	minInt = -maxInt - 1
)

func checkAdd(a, b int) {
	if a > 0 {
		if b > maxInt - a {
			panic("overflow!")
		}
	} else {
		if b < minInt - a {
			panic("underflow!")
		}
	}
}

func checkSub(a, b int) {
	if a > 0 {
		if b < minInt + a {
			panic("overflow!")
		}
	} else {
		if b < a - maxInt {
			panic("underflow!")
		}
	}
}

func Add(a, b int, check bool) int {
	if
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