initpy / go-book Goto Github PK

There two bugs in this chapter in the section "The defer statement".

The func Contents definition is this (line 9):
func Contents(filename string) (string, os.Error) {

and should be like this:
func Contents(filename string) (string, error) {

See the second parameters is not os.Error, but error.

The other bug is in line 22:
if err == os.EOF {

Should be now:
if err == io.EOF {

And you have to add the io import at the beginning.

Greets and nice job!

In the section "How to do this in Go?", the output (results) values are named, but the names used in the code example differ from the names used in the bulleted list that explains the code.

In "A function with a result variable", the code snippet used a var named 'squareroot' while the explanation refers to a variable named 's'.

On this page:

http://go-book.appspot.com/control.html

The link at the bottom for footnote 1 is now a 404 because of this:

https://groups.google.com/group/golang-nuts/browse_thread/thread/e6efaf1932c7b4a2

Hi Big Yuuta,

Kudos! Great Work!

One minor style change I would like to request in your interface section for interface method(s) which return a boolean.

You write :
`

 func (g HumanGroup) Less(i, j int) bool {
       if g[i].age < g[j].age {
           return true
        }
        return false
   }

`
But the following is more concise, cleaner and is inline with Golang Idiom:

`
func (g HumanGroup) Less(i, j int) bool {

    return g[i].age < g[j].age 

}

`

You write:
Here, the interface Men is implemented by both Student and Employee.

However it should read:

Here, the interface Men is implemented by Human, Student and Employee.

Since all three structs make use of Men interface (Human embedded in other two).

http://go-book.appspot.com/slices.html#slice-shorthands

There is a "=" missing character in the next lines:

2: var array = [10]byte {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'}
21: b_slice = a_slice[:]

http://go-book.appspot.com/interfaces.html

Line 42 should be replaced by
s.loan += amount // (again and again and...)
instead of
loan += amount // (again and again and...)

The Group declaration can be also used in more different situation like to declare type-aliasing,interfaces or structs:

type (
        //Type aliasing
    myMap map[string]interface{}
        //structs
    MyStruct struct {


    }
        //Interfaces
    TestInterface interface {

    }

)

"The sum of numbers from 0 to 10 is: 45
The double of this sum is: 90"

Actually, the sum of numbers from 0 to 10 is 55

Your loop only sums numbers from 0 to 9

for i:=0; i<10; i++{
    sum += i

On page http://go-book.appspot.com/slices.html

    a_slice = array[5:] // means: a_slice = array[5:9] thus: a contains: f,g,h,i,j
    a_slice = array[:] // means: a_slice = array[0:9] thus: a contains all array elements.

should be:

    a_slice = array[5:] // means: a_slice = array[5:10] thus: a contains: f,g,h,i,j
    a_slice = array[:] // means: a_slice = array[0:10] thus: a contains all array elements.

...because there are 10 elements, not 9.

page = http://go-book.appspot.com/first.html

In the section called "What is a constant?" the example says
"var y float32
x = 4 * Pi
//when compiled, y == 4 * 3.14"

At first I thought my programming was just terribly terribly rusty, so asked even geekier husband and he also thinks in my humble opinion that the x really should be a y???

ps love the tutorial

On the functions page things are declared as floater and then the code try to access it as the variable f.
Guess someone did some really sloppy variablename changes

import "math"

//return A+B and A*B in a single shot
func MySqrt(floater float64) (squareroot float64, ok bool){
if floater > 0 {
squareroot, ok = math.Sqrt(f), true
}
return squareroot, ok

}

import "math"

//return A+B and A*B in a single shot
func MySqrt(floater float64) (squareroot float64, ok bool) {
if floater > 0 {
squareroot, ok = math.Sqrt(f), true
}
return // Omitting the output named variables, but keeping the "return".

}

Last example of the slices chapter:

- newSlice := make([]byte, l+len(data))
+ newSlive := make([]byte, length + len(data))

Also, need to reassign after append, since we potentially return a copy.

- Append(hello, world)
+ hello = Append(hello, world)

Maybe someone knows author personally, he is not active since late 2012. I hope, he is fine and in good health.

Hi,

first, I would really like to say a big thank you for your work on this book.

I have tried to use Sphinx to generate a PDF document (via LaTeX), but the compilation fails because of some weird chars (ie the chinese ones inside hello.rst).

Even inside my text editor (SublimeText2, using UTF-8), I cannot see them correctly. I've also tried to copy/paste those chars from the web, but it fails too.

Maybe I've done something wrong ?

Thanks again:

Kib².

Hi Yuuta,

In section "Functions As Data" you wrote the code below. Since activity is a slice and not a map you should refrain from using the word variable name "key", instead use variable name "index", since keys are associated with maps not slices or arrays.

Changing the name will make your code much easier to read and understand.

You wrote:

func compose(p phrases, a []activity) (func()){
    return func(){
        for key, value := range a{
            fmt.Print(p[value])
            if key == len(a)-1{
                fmt.Println(".")
            } else {
                fmt.Print(" and ")
            }
        }
    }
}

Should be corrected in following manner (see use of variable name "index" in place of "key")

func compose(p phrases, a []activity) (func()){
    return func(){
        for index, value := range a{
            fmt.Print(p[value])
            if index == len(a)-1{
                fmt.Println(".")
            } else {
                fmt.Print(" and ")
            }
        }
    }
}

In "if-conditional" for one element statement in Max method change index from 1 to 0 for data.Get(x) ."

Currently your code "As Is" will generate following error for one element condition:
panic: runtime error: index out of range

You currently have the following:

func Max(data MaxInterface) (ok bool, max interface{}) {
    if data.Len() == 0{
        return false, nil //no elements in the collection, no Max value
    }
    if data.Len() == 1{ //Only one element, return it alongside with true
        return true, data.Get(1)
    }
    max = data.Get(0)//the first element is the max for now
    m := 0
    for i:=1; i<data.Len(); i++ {
        if data.Bigger(i, m){ //we found a bigger value in our slice
            max = data.Get(i)
            m = i
        }
    }
    return true, max
}

Should be corrected to the following

func Max(data MaxInterface) (ok bool, max interface{}) {
    if data.Len() == 0{
        return false, nil //no elements in the collection, no Max value
    }
    if data.Len() == 1{ //Only one element, return it alongside with true
        return true, data.Get(0)
    }
    max = data.Get(0)//the first element is the max for now
    m := 0
    for i:=1; i<data.Len(); i++ {
        if data.Bigger(i, m){ //we found a bigger value in our slice
            max = data.Get(i)
            m = i
        }
    }
    return true, max
}

Error: Not Found

The requested URL / was not found on this server.

http://go-book.appspot.com/maps.html#deleting-an-entry
The right way to delete a map key is:

delete(myMap, "Key") 

the other syntax in the go-book doesn´t work
assignment count mismatch: 1 = 2 (use delete)

and you have 2 typing errors:

• You must call the map with the name not with the type
• The same mistake in the lower description

In the example output concerning the Hex address of the four vars, the hex values for var "i" and "hello" are the same. I thought they would be different. Right?

Line 42 in the function definition BorrowMoney()

loan += amount
should be
s.loan += amount

var array [10]byte{'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'}

should be

var array = [10]byte{'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'}

Awesome book!! It'd be great if you'd explain a little about ",ok" syntax and when it is generally used (i.e., stores the Boolean, etc)

http://go-book.appspot.com/maps.html#how-to-declare-a-map

• In the example, in line 9, numbers[3] should be numbers["trois"]

• It isn't necessary to declare and then create a make a map

  var numbers map[string] int //declare a map of strings to ints
  numbers = make(map[string]int)

Instead:

var numbers = make(map[string]int)

Dear all!

I'm afraid something happened to the author - he is not been online for 4 years on any his resources. Let's hope, everything is OK with him.
Meanwhile, anyone wills to step in and continue maintaining this book, so we can continue on a new fork and try to complete this book?

yelds = yields