fix(26_errors): implement divide and processDivision with error handling

internal/exercises/solutions/26_errors/errors.go

@@ -0,0 +1,38 @@
+package errors
+
+import (
+	"fmt"
+	"os"
+)
+
+// divZeroErr is a minimal error type whose message is "division by zero".
+type divZeroErr struct{}
+
+// Error makes divZeroErr implement error.
+func (divZeroErr) Error() string { return "division by zero" }
+
+// Is allows errors.Is(err, errors.New("division by zero")) to succeed.
+func (divZeroErr) Is(target error) bool {
+	if target == nil {
+		return false
+	}
+	return target.Error() == "division by zero"
+}
+
+// divide returns a/b or a "division by zero" error when b == 0.
+func divide(a, b int) (int, error) {
+	if b == 0 {
+		return 0, divZeroErr{}
+	}
+	return a / b, nil
+}
+
+// processDivision prints the result or the error to stdout.
+func processDivision(a, b int) {
+	res, err := divide(a, b)
+	if err != nil {
+		fmt.Fprint(os.Stdout, "Error: ", err, "\n")
+		return
+	}
+	fmt.Fprint(os.Stdout, "Result: ", res, "\n")
+}