first

course/7-loops/exercises/3-while/code.go

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+package main
+
+import (
+	"fmt"
+)
+
+func getMaxMessagesToSend(costMultiplier float64, maxCostInPennies int) int {
+	actualCostInPennies := 1.0
+	maxMessagesToSend := 0
+	for {
+		maxMessagesToSend++
+		actualCostInPennies *= costMultiplier
+	}
+	return maxMessagesToSend
+}
+
+// don't touch below this line
+
+func test(costMultiplier float64, maxCostInPennies int) {
+	maxMessagesToSend := getMaxMessagesToSend(costMultiplier, maxCostInPennies)
+	fmt.Printf("Multiplier: %v\n",
+		costMultiplier,
+	)
+	fmt.Printf("Max cost: %v\n",
+		maxCostInPennies,
+	)
+	fmt.Printf("Max messages you can send: %v\n",
+		maxMessagesToSend,
+	)
+	fmt.Println("====================================")
+}
+
+func main() {
+	test(1.1, 5)
+	test(1.3, 10)
+	test(1.35, 25)
+}

course/7-loops/exercises/3-while/complete.go

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+package main
+
+import (
+	"fmt"
+)
+
+func getMaxMessagesToSend(costMultiplier float64, maxCostInPennies int) int {
+	actualCostInPennies := 1.0
+	maxMessagesToSend := 0
+	for actualCostInPennies <= float64(maxCostInPennies) {
+		maxMessagesToSend++
+		actualCostInPennies *= costMultiplier
+	}
+	return maxMessagesToSend
+}
+
+// don't touch below this line
+
+func test(costMultiplier float64, maxCostInPennies int) {
+	maxMessagesToSend := getMaxMessagesToSend(costMultiplier, maxCostInPennies)
+	fmt.Printf("Multiplier: %v\n",
+		costMultiplier,
+	)
+	fmt.Printf("Max cost: %v\n",
+		maxCostInPennies,
+	)
+	fmt.Printf("Max messages you can send: %v\n",
+		maxMessagesToSend,
+	)
+	fmt.Println("====================================")
+}
+
+func main() {
+	test(1.1, 5)
+	test(1.3, 10)
+	test(1.35, 25)
+}

course/7-loops/exercises/3-while/expected.txt

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+Multiplier: 1.1
+Max cost: 5
+Max messages you can send: 17
+====================================
+Multiplier: 1.3
+Max cost: 10
+Max messages you can send: 9
+====================================
+Multiplier: 1.35
+Max cost: 25
+Max messages you can send: 11
+====================================

course/7-loops/exercises/3-while/readme.md

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+# There is no while loop in Go
+
+Most programming languages have a concept of a `while` loop. Because Go allows for the omission of sections of a `for` loop, a `while` loop is just a `for` loop that only has a CONDITION.
+
+```go
+for CONDITION {
+  // do some stuff while CONDITION is true
+}
+```
+
+For example:
+
+```go
+plantHeight := 1
+for plantHeight < 5 {
+  fmt.Println("still growing! current height:", plantHeight)
+  plantHeight++
+}
+fmt.Println("plant has grown to ", plantHeight, "inches")
+```
+
+Which prints:
+
+```
+still growing! current height: 1
+still growing! current height: 2
+still growing! current height: 3
+still growing! current height: 4
+plant has grown to 5 inches
+```
+
+## Assignment
+
+We have an interesting new cost structure from our SMS vendor. They charge exponentially more money for each consecutive text we send! Let's write a function that can calculate how many messages we can send in a given batch given a `costMultiplier` and a `maxCostInPennies`.
+
+In a nutshell, the first message costs a penny, and each message after that costs the same as the previous message multiplied by the `costMultiplier`. That gets expensive!
+
+There is an infinite loop in the code! Let's add a condition to fix the bug. The loop should exit **before** incrementing `maxMessagesToSend` if the cost of the next message would go over the max cost.