publish function sequence

examples.txt

@@ -9,11 +9,11 @@ Arrays
 Slices
 Maps
 Range
-# Functions
-# Multiple Return Values
+Functions
+Multiple Return Values
 # Varadic Functions
-# Closures
-# Recursion
+Closures
+Recursion
 # Defer
 # Panic
 # Pointers

examples/closures/closures.go

@@ -1,20 +1,40 @@
+// Go supports [_anonymous functions_](http://en.wikipedia.org/wiki/Anonymous_function),
+// which can form <a href="http://en.wikipedia.org/wiki/Closure_(computer_science)"><em>closures</em></a>.
+// Anonymous functions are useful when you want to define
+// a function inline without having to name it.
+
 package main
 
 import "fmt"
 
-func makeEvenGenerator() func() uint {
-    i := uint(0)
-    return func() uint {
-        i += 2
+// This function `intSeq` returns another function, which
+// we define anonymously in the body of `intSeq`. The
+// returned function _closes over_ the variable `i` to
+// form a closure.
+func intSeq() func() int {
+    i := 0
+    return func() int {
+        i += 1
         return i
     }
 }
 
 func main() {
-    nextEven := makeEvenGenerator()
-    fmt.Println(nextEven())
-    fmt.Println(nextEven())
-    fmt.Println(nextEven())
-}
 
-// todo: note example of first-class functions.
+    // We call `intSeq`, assigning the result (a function)
+    // to `nextInt`. This function value captures its
+    // own `i` value, which will be updated each time
+    // we call `nextInt`.
+    nextInt := intSeq()
+
+    // See the effect of the closure by calling `nextInt`
+    // a few times.
+    fmt.Println(nextInt())
+    fmt.Println(nextInt())
+    fmt.Println(nextInt())
+
+    // To confirm that the state is unique to that
+    // particular function, create and test a new one.
+    newInts := intSeq()
+    fmt.Println(newInts())
+}

examples/closures/closures.sh

@@ -0,0 +1,8 @@
+$ go run closures.go
+1
+2
+3
+1
+
+# The last feature of functions we'll look at for now is
+# recursion.

examples/functions/functions.go

@@ -1,34 +1,26 @@
-// Funcations are critical in Go as in any other language.
-// We'll look at some basic examples first.
+// _Functions_ are central in Go. We'll learn about
+// functions with a few different examples.
 
 package main
 
 import "fmt"
 
-// The syntax is `func name(args) returns { body }`. Note
-// the the types of arguments come after their name.
-// In this case we're taking a slice of floats and
-// returning a single float value.
-func avg(vals []float64) float64 {
-    total := 0.0
-    for _, val := range vals {
-        total += val
-    }
-    // Go requires an expliciti return, i.e. it won't
+// Here's a function that takes two `int`s and returns
+// their sum as an `int`.
+func plus(a int, b int) int {
+
+    // Go requires explicit returns, i.e. it won't
     // automatically return the value of the last
     // expression.
-    return total / float64(len(vals))
+    return a + b
 }
 
 func main() {
-    input := []float64{98, 93, 77, 82, 83}
-    fmt.Println(input)
+
     // Call a function just as you'd expect, with
     // `name(args)`.
-    output := avg(input)
-    fmt.Println(output)
+    res := plus(1, 2)
+    fmt.Println("1+2 =", res)
 }
 
-// There are several other features to Go functions,
-// including multiple return values and varargs, which
-// we'll look at next.
+// todo: coalesced parameter types

examples/functions/functions.sh

@@ -0,0 +1,5 @@
+$ go run functions.go 
+1+2 = 3
+
+# There are several other features to Go functions. One is
+# multiple return values, which we'll look at next.

examples/multiple-return-values/multiple-return-values.go

@@ -1,4 +1,4 @@
-// Go has built-in support for multiple return values.
+// Go has built-in support for _multiple return values_.
 // This feature is used often in idiomatic Go, for example
 // to return both result and error values from a function.
 
@@ -6,15 +6,16 @@ package main
 
 import "fmt"
 
-// The `(int, int)` in this signature shows that the
-// function returns 2 ints.
+// The `(int, int)` in this function signature shows that
+// the function returns 2 `int`s.
 func vals() (int, int) {
     return 3, 7
 }
 
 func main() {
+
     // Here we use the 2 different return values from the
-    // call, i.e. perform multiple assignement.
+    // call with _multiple assignment_.
     a, b := vals()
     fmt.Println(a)
     fmt.Println(b)
@@ -24,3 +25,6 @@ func main() {
     _, c := vals()
     fmt.Println(c)
 }
+
+// todo: named return parameters
+// todo: naked returns

examples/multiple-return-values/multiple-return-values.sh

@@ -2,3 +2,6 @@ $ go run multiple-return-values.go
 3
 7
 7
+
+# Another key aspect of functions in Go is their ability
+# to form closures, which we'll look at next.

examples/recursion/recursion.go

@@ -1,14 +1,20 @@
+// Go supports
+// <a href="http://en.wikipedia.org/wiki/Recursion_(computer_science)"><em>recursive functions</em></a>.
+// Here's a classic factorial example.
+
 package main
 
 import "fmt"
 
-func factorial(x uint) uint {
-    if x == 0 {
+// This `fact` function calls itself until it reaches the
+// base case of `fact(0)`.
+func fact(n int) int {
+    if n == 0 {
         return 1
     }
-    return x * factorial(x-1)
+    return n * fact(n-1)
 }
 
 func main() {
-    fmt.Println(factorial(7))
+    fmt.Println(fact(7))
 }

examples/recursion/recursion.sh

@@ -0,0 +1,2 @@
+$ go run recursion.go 
+5040