Add remaining code of chapter 03

chapter_03/activity_3.01/main.go

@@ -0,0 +1,21 @@
+package main
+
+import "fmt"
+
+func salesTax(cost float64, taxRate float64) float64 {
+
+  return cost * taxRate / 100
+
+}
+
+func main() {
+
+  taxTotal := 0.0
+
+  taxTotal = salesTax(0.99, 7.5)
+  taxTotal += salesTax(2.75, 1.5)
+  taxTotal += salesTax(0.87, 2.0)
+
+  fmt.Println("Sales Tax Total:", taxTotal)
+
+}

chapter_03/activity_3.02/main.go

@@ -0,0 +1,94 @@
+package main
+
+import (
+  "errors"
+  "fmt"
+)
+
+const (
+  goodScore      = 450
+  lowScoreRation = 10
+  goodScoreRatio = 20
+)
+
+var (
+  ErrCreditScore = errors.New("invalid credit score")
+  ErrIncome      = errors.New("income invalid")
+  ErrLoanAmount  = errors.New("loan amount invalid")
+  ErrLoanTerm    = errors.New("loan term not a multiple of 12")
+)
+
+func checkLoan(creditScore int, income float64,
+  loanAmount float64, loanTerm float64) error {
+
+  interest := 20.0
+
+  if creditScore >= goodScore {
+    interest = 15
+  }
+
+  if creditScore < 1 {
+    return ErrCreditScore
+  }
+
+  if income < 1 {
+    return ErrIncome
+  }
+
+  if loanAmount < 1 {
+    return ErrLoanAmount
+  }
+
+  if loanTerm < 1 || int(loanTerm)%12 != 0 {
+    return ErrLoanTerm
+  }
+
+  rate := interest / 100
+
+  payment := ((loanAmount * rate) / loanTerm) + (loanAmount / loanTerm)
+  totalInterest := (payment * loanTerm) - loanAmount
+
+  approved := false
+
+  if income > payment {
+    ratio := (payment / income) * 100
+    if creditScore >= goodScore && ratio < goodScoreRatio {
+      approved = true
+    } else if ratio < lowScoreRation {
+      approved = true
+    }
+  }
+
+  fmt.Println("Credit Score    :", creditScore)
+  fmt.Println("Income          :", income)
+  fmt.Println("Loan Amount     :", loanAmount)
+  fmt.Println("Loan Term       :", loanTerm)
+  fmt.Println("Monthly Payment :", payment)
+  fmt.Println("Rate            :", interest)
+  fmt.Println("Total Cost      :", totalInterest)
+  fmt.Println("Approved        :", approved)
+  fmt.Println("")
+
+  return nil
+
+}
+
+func main() {
+
+  // Approved
+  fmt.Println("Applicant 1")
+  fmt.Println("-----------")
+  err := checkLoan(500, 1000, 1000, 24)
+  if err != nil {
+    fmt.Println("Error:", err)
+  }
+
+  // Denied
+  fmt.Println("Applicant 2")
+  fmt.Println("-----------")
+  err = checkLoan(350, 1000, 10000, 12)
+  if err != nil {
+    fmt.Println("Error:", err)
+  }
+
+}

chapter_03/exercise_3.05/main.go

@@ -0,0 +1,19 @@
+package main
+
+import "fmt"
+
+func main() {
+
+  logLevel := "デバッグ"
+
+  // For a string value, the range clause iterates over the
+  // Unicode code points in the string starting at byte index 0.
+  // On successive iterations, the index value will be the index
+  // of the first byte of successive UTF-8-encoded code points
+  // in the string, and the second value, of type rune,
+  // will be the value of the corresponding code point.
+  for index, runeVal := range logLevel {
+    fmt.Println(index, string(runeVal))
+  }
+
+}

chapter_03/rune/main.go

@@ -0,0 +1,28 @@
+package main
+
+import "fmt"
+
+func main() {
+
+  username := "Sir_King_Über"
+
+  // Print bytes directly
+  for i := 0; i < len(username); i++ {
+    fmt.Print(username[i], " ")
+  }
+  fmt.Printf("\n")
+
+  // Print bytes converted to string
+  for i := 0; i < len(username); i++ {
+    fmt.Print(string(username[i]), " ")
+  }
+  fmt.Printf("\n")
+
+  // Print bytes converted to runes
+  runes := []rune(username)
+  for _, value := range runes {
+    fmt.Print(string(value), " ")
+  }
+  fmt.Printf("\n")
+
+}