From 50b1c7b2aa3080758ad06dd5fa8d41eae0511445 Mon Sep 17 00:00:00 2001
From: asandikci <git@aliberksandikci.com.tr>
Date: Mon, 17 Jul 2023 13:11:00 +0300
Subject: [PATCH] Functions

---
 2moretypes/function.go | 105 +++++++++++++++++++++++++++++++++++++++++
 exercises/fibonacci.go |  24 ++++++++++
 2 files changed, 129 insertions(+)
 create mode 100644 2moretypes/function.go
 create mode 100644 exercises/fibonacci.go

diff --git a/2moretypes/function.go b/2moretypes/function.go
new file mode 100644
index 0000000..04f4aa0
--- /dev/null
+++ b/2moretypes/function.go
@@ -0,0 +1,105 @@
+package main
+
+import (
+	"fmt"
+	"math"
+	"reflect"
+)
+
+func compute(fn func(float64, float64) float64) float64 {
+	return fn(2, 7)
+}
+
+func incrementer() func() int { // returns a function -that requires and returns an int value-
+	curVal := 0
+	return func() int {
+		curVal += 1
+		return curVal
+	}
+}
+
+func incrementWithNum() func(int) int { // returns a function -that requires and returns an int value-
+	curVal := 0
+	return func(i int) int {
+		curVal += i
+		return curVal
+	}
+}
+
+func adder(a int) func(int) int { // gets first value with adder(int), returns a function -that requires and returns an int value-
+	return func(b int) int {
+		return a + b
+	}
+}
+
+func main() {
+	fmt.Println("Includes function values, closures and other function related subject, if you want to see functions basics, go to 0basics/basics.go > Section \"Functions\"")
+
+	fmt.Println("Functions are values too, They can be passed around just like other values")
+
+	sum := func(x, y float64) float64 {
+		return float64(x + y)
+	}
+	fmt.Println(sum(2, 3))
+	fmt.Println(sum)
+	fmt.Println(&sum)
+	fmt.Println(reflect.TypeOf(sum))
+	fmt.Println(reflect.TypeOf(sum).Kind())
+
+	fmt.Printf("\n\n")
+	fmt.Println("Function values may be used as function arguments and return values")
+	fmt.Println(compute(sum))
+	fmt.Println(compute(math.Pow))
+	fmt.Printf("%p\n", compute)
+	fmt.Println(reflect.TypeOf(compute))
+	fmt.Println(reflect.TypeOf(compute).Kind())
+
+	fmt.Printf("\ncompute a function that gets a function as an argument (that gets two float64 values and returns float64) and returns float64\n\n\n")
+
+	fmt.Println("Go functions may be closures")
+	fmt.Println("With this feature inner functions can read outer functions values, use them. Also with assigning it to a variable we can use same function from scratch")
+	fmt.Println("A bit confusing but just see the examples:")
+
+	// SECTION incrementer()
+	newInc1 := incrementer()
+	fmt.Println(newInc1())
+	fmt.Println(newInc1())
+	fmt.Println(newInc1())
+
+	fmt.Printf("\n")
+
+	newInc1 = incrementer() // you can initialize again
+	fmt.Println(newInc1())
+
+	newInc2 := incrementer()
+	newInc2()
+	newInc2()
+	newInc2()
+	newInc2()
+	newInc2()
+	fmt.Println(newInc2())
+
+	fmt.Println(newInc1())
+
+	fmt.Printf("\n\n")
+	// !SECTION
+	// SECTION incrementWithNum()
+	numInc1 := incrementWithNum()
+	// fmt.Println(numInc1()) // ERROR, not enough arguments in call to numInc1
+	fmt.Println(numInc1(4)) // Increments curVal by 4 and print out
+	fmt.Println(numInc1(3)) // Increments curVal by 3 and print out
+	fmt.Println(numInc1(2)) // "" 2 ""
+	fmt.Println(numInc1(1)) // "" 1 ""
+
+	fmt.Printf("\n\n")
+	// !SECTION
+	// SECTION adder()
+
+	myAdder1 := adder(5)
+	fmt.Println(myAdder1(1)) // 5+1=6
+	fmt.Println(myAdder1(8)) // 5+8=13
+
+	myAdder2 := adder(8)
+	fmt.Println(myAdder2(myAdder1(3))) // 8 + (5+3)
+
+}
diff --git a/exercises/fibonacci.go b/exercises/fibonacci.go
new file mode 100644
index 0000000..89b10a9
--- /dev/null
+++ b/exercises/fibonacci.go
@@ -0,0 +1,24 @@
+package main
+
+// exercise link: https://go.dev/tour/moretypes/26
+
+import "fmt"
+
+// fibonacci is a function that returns
+// a function that returns an int.
+func fibonacci() func() int {
+	first := 0
+	second := 1
+	return func() int {
+		second += first
+		first = second - first
+		return first
+	}
+}
+
+func main() {
+	f := fibonacci()
+	for i := 0; i < 10; i++ {
+		fmt.Println(f())
+	}
+}