first

course/10-advanced_functions/exercises/3-currying/code.go

@@ -0,0 +1,47 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+)
+
+// getLogger takes a function that formats two strings into
+// a single string and returns a function that formats two strings but prints
+// the result instead of returning it
+func getLogger(formatter func(string, string) string) func(string, string) {
+	// ?
+}
+
+// don't touch below this line
+
+func test(first string, errors []error, formatter func(string, string) string) {
+	defer fmt.Println("====================================")
+	logger := getLogger(formatter)
+	fmt.Println("Logs:")
+	for _, err := range errors {
+		logger(first, err.Error())
+	}
+}
+
+func colonDelimit(first, second string) string {
+	return first + ": " + second
+}
+func commaDelimit(first, second string) string {
+	return first + ", " + second
+}
+
+func main() {
+	dbErrors := []error{
+		errors.New("out of memory"),
+		errors.New("cpu is pegged"),
+		errors.New("networking issue"),
+		errors.New("invalid syntax"),
+	}
+	test("Error on database server", dbErrors, colonDelimit)
+
+	mailErrors := []error{
+		errors.New("email too large"),
+		errors.New("non alphanumeric symbols found"),
+	}
+	test("Error on mail server", mailErrors, commaDelimit)
+}

course/10-advanced_functions/exercises/3-currying/complete.go

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+package main
+
+import (
+	"errors"
+	"fmt"
+)
+
+// getLogger takes a function that formats two strings into
+// a single string and returns a function that formats two strings but prints
+// the result instead of returning it
+func getLogger(formatter func(string, string) string) func(string, string) {
+	return func(first, second string) {
+		fmt.Println(formatter(first, second))
+	}
+}
+
+// don't touch below this line
+
+func test(first string, errors []error, formatter func(string, string) string) {
+	defer fmt.Println("====================================")
+	logger := getLogger(formatter)
+	fmt.Println("Logs:")
+	for _, err := range errors {
+		logger(first, err.Error())
+	}
+}
+
+func colonDelimit(first, second string) string {
+	return first + ": " + second
+}
+func commaDelimit(first, second string) string {
+	return first + ", " + second
+}
+
+func main() {
+	dbErrors := []error{
+		errors.New("out of memory"),
+		errors.New("cpu is pegged"),
+		errors.New("networking issue"),
+		errors.New("invalid syntax"),
+	}
+	test("Error on database server", dbErrors, colonDelimit)
+
+	mailErrors := []error{
+		errors.New("email too large"),
+		errors.New("non alphanumeric symbols found"),
+	}
+	test("Error on mail server", mailErrors, commaDelimit)
+}

course/10-advanced_functions/exercises/3-currying/expected.txt

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+Logs:
+Error on database server: out of memory
+Error on database server: cpu is pegged
+Error on database server: networking issue
+Error on database server: invalid syntax
+====================================
+Logs:
+Error on mail server, email too large
+Error on mail server, non alphanumeric symbols found
+====================================

course/10-advanced_functions/exercises/3-currying/readme.md

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+# Currying
+
+Function currying is the practice of writing a function that takes a function (or functions) as input, and returns a new function.
+
+For example:
+
+```go
+func main() {
+  squareFunc := selfMath(multiply)
+  doubleFunc := selfMath(add)
+  
+  fmt.Println(squareFunc(5))
+  // prints 25
+
+  fmt.Println(doubleFunc(5))
+  // prints 10
+}
+
+func multiply(x, y int) int {
+  return x * y
+}
+
+func add(x, y int) int {
+  return x + y
+}
+
+func selfMath(mathFunc func(int, int) int) func (int) int {
+  return func(x int) int {
+    return mathFunc(x, x)
+  }
+}
+```
+
+In the example above, the `selfMath` function takes in a function as its parameter, and returns a function that itself returns the value of running that input function on its parameter.
+
+## Assignment
+
+The Mailio API needs a very robust error-logging system so we can see when things are going awry in the back-end system. We need a function that can create a custom "logger" (a function that prints to the console) given a specific formatter.
+
+Complete the `getLogger` function. It should `return` *a new function* that prints the formatted inputs using the given `formatter` function. The inputs should be passed into the formatter function in the order they are given to the logger function.