notes.md

Golang 101

2024-06-24

1. Everything is organized as Packages.
2. All files must have only 1 entrypoint. main() is the entrypoint and gets executed on its own.
3. To initialize a go project. Run the following command

go mod init <folder name>

This creates a go.mod file. Which defines go version and the module name. 4. Main function doesn't accept any arguments. Neither returns anything. 5. Go package is a collection of source files. It gives various functionalities. Containers of various functionalities that go gives you for ready to use.

2024-06-25

VARIABLES

1. If variable is constant then use const keyword before variable name. Else use var.

const conferenceTickets = 50

As number of available tickets is fixed i.e 50.

2. To print formatted data. There is a function printf present in fmt package. %v is the default. PS: For more details check printf documentation in fmt standard library.

DATA TYPES

1. If we are assigning the value to a variable and declaring the variable at the same time. Then, Go implicitly assigns the data type to variable based on the value.

2. If variable is only declared and no value is assigned. Then we need to explicitly mention the data type of variable.

var userName string

3. %T is used to print type of the variable

4. Syntatic Sugar in GO. Works only for variables and not constants.

Instead of writing

var conferenceName string = "Go Conference"

We can write it as

conferenceName := "Go Conference"

Asking User for Input

1. Pointer is variable that points to memory address of another variable.

fmt.Scan(&userName)

2024-06-26

Loops and Control Statement

2024-06-27

Array and Slices

1. Array can contain only elements with same data type.
2. Array size and type has to be declared in the beginning.

Below is the syntax to initialize empty array

var bookings[50]string{}

Syntax to initialize array with list of elements.

var bookings = [50]string{"Mridu", "Sakshi", "Shubh"}

3. Dynamic arrays are slices. Slices are used when size is not fixed.

var bookings[]string

4. To add an element to a slice. Use append. First argument to append is slice. Syntax.

bookings = append(bookings, firstName + " " + lastName) 

Infinite Loop

No exit condition

for {

}

Break and Continue

1. break breaks out of the loop.
2. continue moves to next iteration without executing remaining part of the body.

Strings

1. Can be accessed using square bracktes prints the ASCII value of the character

s := "Hello World" 
fmt.Println(s[0])

2. Use %c to print the character of string.

s := 'Hello World'
fmt.Printf("%c", s[0])

3. Printing a part of the string.

// prints total 5 charaters. 0 to 4
fmt.Println(s[0:5])
fmt.Println(s[:5])

4. Print string given only the starting index. Prints from W.

fmt.Println(s[6:])

5. String concat works normally. This would print Hello World Again

s = s + " Again"
fmt.Println(s)

7. String Literals

fmt.Println("Hello\nWorld")
fmt.Println("Hello\tWorld")
fmt.Println("Hello\bWorld")

String Library

1. Built-in method ToUpper for converting string from lower case to uppercase.

s := "Hello World"
fmt.Println(strings.ToUpper(s))

2. Built-in method ToLower for converting string from upper case to lower case.

fmt.Println(strings.ToLower(s))

3. For check if string contains the prefix.

fmt.Println(strings.HasPrefix(s, "Hello"))

4. For checking if string contains suffix

fmt.Println(strings.HasSuffix(s, "World))

5. Replace. 1st argument - full string. 2nd argument - string you want to replace 3rd argument - new string you want to replace old string with 4th argument - If the string to be replaced appear more than once. Count of strings you want to replace.

fmt.Println(strings.Replace(s, "Hello", "World", 2))

2024-07-14

• Learned to return error by solving collatz conjuncture exercism problem. Using error standard library.

import "error"
err := error.New("value of n cannot be given as 0")

• Used math standard library for calculating exponent to the base 10. Output returned is in float64. Type cast it based on your need.

import "math"
math.Pow(float64(10), float64(index1))

• Used library strconv for converting integer to string.

import strconv
strconv.Itoa(42)

Aug 8 2024

1. os.ReadFile(<filepath>) reads file all at once.
2. os.Open(<filepath>) opens the file.