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Enum is a data type with mutiple possible variants. To declare an enum, write enum and use a code block with the options, separated by commas. These options are called as variants.
A borrowed reference allow you to access data without taking ownership of it. The & operator creates a borrowed reference to a variable.
If we want to pass the reference of string it can be done as follows-
Here the program uses tuple to pass the string refernce back with the length
{
let inner_variable = String::from("welcome");
let (note, note_length) = wlecome_note(inner_variable);
println!("Length of {} is {}", note, note_length);
}
fn wlecome_note(note: String) -> (String, usize){
let note_length = note.len();
(note, note_length)
}
Output-
Length of welcome is 7
This is a tedious way, instead the string refernce can be borrowed in the function, unaffecting the refernece in main block.
{
let inner_variable = String::from("welcome");
let note_length = wlecome_note(&inner_variable);
println!("Length of {} is {}", inner_variable, note_length);
}
fn wlecome_note(note: &String) -> usize{
let note_length = note.len();
note_length
}
Here & operator borrows the reference temporary into the note variable and when the it comes out of scope doesn’t affect the inner_variable in main block. This process is called as borrowing refernce.
Summary
Borrowing – Access data without taking ownership of it
Borrowing – Create reference using the borrow operator &
When working with reference its important to understand which variable own the data
Mutable reference
In the above code we didn’t change the reference i.e. the nore variable in wlecome_note function. To do so use push_str() method.
{
let inner_variable = String::from("welcome");
let note_length = wlecome_note(&inner_variable);
println!("Length of {} is {}", inner_variable, note_length);
}
fn wlecome_note(note: &String) -> usize{
let note_length = note.len();
note.push_str(" to the Rust programming"); // Error
note_length
}
This gives a compiler error.
The error is data we are referencing is not mutable reference. We have to tell Rust that it is a mutable reference. For this use &mut keyword .
{
let mut inner_variable = String::from("welcome");
let note_length = wlecome_note(&mut inner_variable);
println!("Length of {} is {}", inner_variable, note_length);
}
fn wlecome_note(note: &mut String) -> usize{
note.push_str(" to the Rust programming");
let note_length = note.len();
note_length
}
Output-
Length of welcome to the Rust programming is 31
This updates the borrowed reference and main block has the updated data.
Summary-
When using a mutable reference, you cannot create other references, to prevent the data races.
If you’re only working with regular immutable references, then you can create as many of those as you want pointing to the same variable. The restriction comes in when you try to create references in addition to the one allowed mutable reference. Even if those additional references are immutable, it creates the potential for problems and the Rust compiler will not allow it.
Dangling references
A dangling reference is a reference to something that no longer exists at the referenced location.
A dangling reference can occur when a function returns a reference to a value that is owned by a variable whose scope is limited to that function.
It’s easy to erroneously create a dangling pointer—a pointer that references a location in memory that may have been given to someone else—by freeing some memory while preserving a pointer to that memory. In Rust, by contrast, the compiler guarantees that references will never be dangling references: if you have a reference to some data, the compiler will ensure that the data will not go out of scope before the reference to the data does.
{
let reference_to_nothing = dangle();
}
fn dangle() -> &String {
let s = String::from("hello");
&s // Error
}
Solution-
Remove borrow operator
{
let reference_to_nothing = dangle();
println!("Dangling refernce data is {}", reference_to_nothing);
}
fn dangle() -> String { // Remove borrow operator
let s = String::from("hello");
s // Remove borrow operator
}
Output-
Dangling refernce data is hello
Slices
Borrowing a data type with sequence of elements, if we only want subset of elements we use Slice. Commonly used slices is String &str
let message = String::from("Welcome to Rust");
println!("message is {}", message);
let last_word = &message[10..];
println!("last word is - {}", last_word);
Here we sliced the string to only get the last word i.e. Rust. Here the message variable is still the owner of the string. and last_word variable points to the address of the slice.
Output
message is Welcome to Rust
last word is Rust
&String != &str – String Type is not String Literal
With strings, a borrowed reference to a string is not equivalent to a slice from the string. They’re different data types.
Dref Coercion- The deref gives the compiler the ability to take a value of any type that implements Deref and call the deref method to get an & reference that it knows how to dereference
Summary –
Borrow the string object to slice the string &my_string[4..]
Once you create one mutable reference to a variable you cannot create any other references to it.
A slice only stores a pointer to the heap data, along with length information. The slice doesn’t need to keep track of capacity because the slice will never own anything on the heap.
A string reference will point to an actual string on the stack, which in turn points to and owns the string data that lives on the heap. A slice will only store a pointer to the heap data.
Ownership in Rust where the variables are responsible for creating their own resources.
Every value is owned by one, and only one variable at a time
When the owning variable goes out of scope, the value is dropped
Memory Management in Rust and other languages
Memory Management
Feature
Advantage
Disadvantage
Manual Allocation and Deallocation
Progammer responsible for memory mgmt C/C++ – malloc() and free()
Programmer has lots of control
Memory leaks
Garbage Collection
Automatically cleans up memory Java, Python, C#, Ruby, Go
Its easy as programmer don’t have to worry about memory mgmt
Can lead to wasteful memory Can run at inconvenient times
Ownership
Variables are responsible for freeing their own resources Rust
Safe, Effecient (when data will be dropped at compile time)
Requires understanding of ownership
Example – Every value is owned by one, and only one variable at a time
{
1let inner_variable = String::from("Welcome");
println!("inner_valriable is {}", inner_variable);
}2
println!("inner_valriable is {}", inner_variable);3 // Error
The memory is allocated at this line of code in Stack and points to heap where the data is stored. ↩︎
Deallocates/drops the data in heap and stack since the scope is complete ↩︎
Error – Variable is nto available here since its deallocated in prevous line. ↩︎
Example – When the owning variable goes out of scope, the value is dropped
Ownership is moved to another variable (outer_variable)
let outer_variable : String;
{
let inner_variable = String::from("welcome");
println!("inner_valriable is {}", inner_variable);
outer_variable = inner_variable;
}
println!("outer_variable is {}", outer_variable);
X The above example breaks the rule since 2 variables assigned to same address in heap. Hence this is called as move the inner_varaible is out of scope.
let outer_variable : String;
{
let inner_variable = String::from("welcome");
outer_variable = inner_variable;
println!("inner_valriable is {}", inner_variable); // Error
}
println!("outer_variable is {}", outer_variable);
Since the inner_variable scope is moved to outer_variable the memory allocation is dropped.
Copy works only for stack data types, such as integer and floating point
Cloning the data
The clone() method is used to create a deep copy of heap data.
String data is not implicitly copied and must be explicitly cloned using the clone() method.
let outer_variable : String;
{
let inner_variable = String::from("welcome");
outer_variable = inner_variable.clone();
println!("inner_valriable is {}", inner_variable);
}
println!("uter_valriable is {}", outer_variable);
Clone creates a new heap and copies the data and binds to the stack.
Output
inner_valriable is welcome
outer_valriable is welcome
Copy occurs implicitly; cloning must be done explicitly
Transfering Ownership
When a function takes ownership of a value, it becomes responsible for that value and its associated data. The function can then do whatever it wants with the data, including modify or delete it. If the function doesn’t need the data anymore, it will be dropped.
Hence Rust is Safe i.e. at compile time the program knows when the variables are accessible and efficient since it knows when to drop the data from memory.
Summary-
Shadowing allows you to declare a new variable with the same name as an existing variable.
Copying allows you to duplicate a value that is stored on the stack.
The heap can dynamically add and remove data.
The stack stores values in sequential order. The stack adds and removed data as LIFO.
Copying data on the stack occurs implicitly, whereas cloning data on the heap must be done explicitly using the clone method.
The String data type stores the sequence of characters that make up the String on the heap and it stores a structure containing a pointer to the heap data, the String’s length, and its capacity on the stack.
0 47.60 npm notice Beginning October 4, 2021, all connections to the npm registry – including for package installation – must use TLS 1.2 or higher. You are currently using plaintext http to connect. Please visit the GitHub blog for more information: https://github.blog/2021-08-23-npm-registry-deprecating-tls-1-0-tls-1-1/
An if expression is used to control which code gets executed based on conditions the program can evaluate at runtime.
Short hand to use if condition.
let y =true;
let x = if y {1} else {0};
println!("x is {}", x)
Output-
x is 1
Loop
Rust provides a loop keyword to indicate an infinite loop. Unless stopped manually or with a break staement, loop can go infinitely.
Infinite loop example. Manually stop the program
let mut count=0;
loop{
count += 1;
println!("count is {}", count)
}
break keyword
Immediately exit the loop and continue execution forward. The break statement can be used to prematurely exit all types of loop constructs.
Here once loop is at 10 it breaks the loop and continues further execution
let mut count=0;
loop{
if count == 10{
println!("breaking the loop on count {}", count);
break;
}
count += 1;
println!("count is {}", count);
}
println!("Continues execution.");
Output-
count is 1
count is 2
count is 3
count is 4
count is 5
count is 6
count is 7
count is 8
count is 9
count is 10
breaking the loop on count 10
Continues execution.
break with return
In the below code break can return the result or the reason the loop is stopped to the execution program.
let mut count=0;
let result = loop{
if count == 10{
println!("breaking the loop on count {}", count);
break count * 5
}
count += 1;
println!("count is {}", count);
};
println!("Count result is - {} * 5 = {}", count, result);
Output-
count is 1
count is 2
count is 3
count is 4
count is 5
count is 6
count is 7
count is 8
count is 9
count is 10
breaking the loop on count 10
Count result is - 10 * 5 = 50
Predicate (while) loop
Predicate loop that repeats a block of code while the condition is true. Begins by evaluating a boolean condition and breaks/completes when the condition is false. A while-loop repeats a block of code while a condition is true.
Here break statement can be used to terminate the loop but it doesnot return the value as comapred to loop
let mut count=0;
while count < 5 {
count += 1;
println!("count is {}", count);
}
Output
count is 1
count is 2
count is 3
count is 4
count is 5
Iteratorfor loop
The for in construct can be used to iterate through an Iterator. One of the easiest ways to create an iterator is to use the range notation a..b. This yields values from a (inclusive) to b (exclusive) in steps of one.
For loops are mainly used to iterate over the items in a collection, and execute some code for each one so that you can process each item in the collection individually. If you need to repeat a block of code for a specific number of times that you know before starting the loop, you can use a ‘for’ loop to iterate over the range from zero to that value.
for n in 1..5{
print!("{}\t", n)
}
loop 1..5, here 1 is inclusive while 5 is exclusive. Print! won;t print in new line.
Output
1 2 3 4
user iter() methodto iterate over the list-
let message= ['r','u','s','t'];
for msg in message.iter(){
print!("{}\t", msg)
}
Output-
r u s t
Iterator with index
At times apart from the element in the array or list and index is required. This can be achieved by using enumerate() method
let message= ['r','u','s','t'];
for (index,msg) in message.iter().enumerate(){
println!("item {} is {}", index, msg)
}
Output-
item 0 is r
item 1 is u
item 2 is s
item 3 is t
Nested loops
Example here taking row and columns and printing those values in a nested loop i.e. for loop(rows) wthin for loop(columns)
let matrix = [[1,2,3],[10,20,30], [100,200,300]];
for row in matrix.iter(){
for col in row.iter(){
print!("{}\t", col);
}
println!();
}
Output-
All the columsn are printed in same line while row in new line.
variable.iter() is used to iterate between rows and columns
1 2 3
10 20 30
100 200 300
Modify the value in for loop using iter_mut()
Sometimes value in the collection needs to be updated. This can be done by iterating and updating the values. To do so use iter_mut() function as follows-
let mut matrix = [[1,2,3],[10,20,30], [100,200,300]];
for row in matrix.iter_mut(){
for col in row.iter_mut(){
*col += 5;
print!("{}\t", col);
}
println!();
}
Notice here the iter_mut() method is used which give a reference to the mmeory allocated for the collection. In the next line *col is used to deference so that a addition operation can be performed.
Using * is called “dereferencing”.
Output-
6 7 8
15 25 35
105 205 305
Rust has two rules for mutable and immutable references. They are very important, but also easy to remember because they make sense.
Rule 1: If you have only immutable references, you can have as many as you want. 1 is fine, 3 is fine, 1000 is fine. No problem.
Rule 2: If you have a mutable reference, you can only have one. Also, you can’t have an immutable reference and a mutable reference together.
Functions are use to efficient programming and eliminates the need to constantly rewrite code.
Rust is a strictly typed language and therefore needs to know the data type for all variables at compilation.
When there is not a specified return value, the function will return the unit data type which is represented as () and indicates there is no other meaningful values that could be returned. A statement does not return a value.
In the below example we can see how a function can be defined and called from the main.
Function without and with parameters. Define the parmeter data type and return data type.
fn main(){
display_message();
display_message_with_parameters(10);
let addition = add_numbers(10, 20);
println!("Addition of 2 number is {}", addition);
}
fn display_message(){
println!("Display message....");
}
fn display_message_with_parameters(value : i8){
println!("Function paramter value is {}", value);
}
fn add_numbers(param1: i8, param2: i8) -> i8{
param1 + param2
}
Output-
Display message....
Function paramter value is 10
Addition of 2 number is 30
Diverging Functions
Diverging functions never return. They are marked using !, which is an empty type.
fn foo() -> ! {
panic!("This call never returns.");
}
Empty return functions
Function return empty (). It doesn’t return anything but returns back to caller
fn some_fn() {
()
}
fn main() {
let _a: () = some_fn();
println!("This function returns and you can see this line.");
}
In Rust arrays are stored in contigious section of memory locations and sorted in order. They are fixed length and cannot be dynamically resize, containing elements of same data type.
A fix size array denotes [T;N]. where T denotes element type i.e. i32, u64 etc. and N denoted non-negative compile time constant size. This means compiler needs to know before running the code the size of array.
One way of declaring an array is to have the values comma seperated in square brackets e.g.- [1, 2, 3]
Example-
let fruits = ["apple", "orange"];
let selected_fruit = fruits[0];
// Retrieve first element of an array.
println!("Selected fruit is - {}", selected_fruit);
Output-
Selected fruit is - apple
To modify the value in the array make the array mutable and change the value of an element in array, in this case first element.
let mut fruits = ["apple", "orange"];
fruits[0]= "mango";
let selected_fruit = fruits[0];
println!("Selected fruit is - {}", selected_fruit);
Output-
Selected fruit is - mango
Repeat expression – Declaring arrays with the data type and length [expr, N] where N is the times to repeat expression (expr).
Note that [expr; 0] is allowed, and produces an empty array. This will still evaluate expr, however, and immediately drop the resulting value, so be mindful of side effects.
let numbers : [i32; 5]; // declare array
numbers= [1, 3, 5, 7, 9]; // initalize array
println!("Selected number - {}", numbers[0]); // print first element
Output-
Selected number - 1
Compiler Errors-
If array is not initalised and the element of array is tried to access the compiler thorws an error-
let numbers : [i32; 5];
println!("Selected number - {}", numbers[0]);
Solution-
let numbers : [i32; 5];
numbers = [0;5]; // All elements has value 0
println!("Selected number - {}", numbers[0]);
Output-
Selected number - 0
Compiler Errors-
Index out of bounds – if the element accessed is larger than the array length.
let numbers : [i32; 5];
println!("Selected number - {}", numbers[5]);
The array length is 5 and index starts from 0, so the last index is 4. But in above program the index 5 is trying to access hence error
Solution-
The element accessed here is the last element i.e. index 4.
let numbers : [i32; 5];
numbers = [0;5]; // all elements has value 0
println!("Selected number - {}", numbers[4]);/ Compiles successfully
Count of elements
Get the length of an array using extension function len()
let numbers : [i32; 5];
numbers = [0;5];
println!("Length of numbers is {}", numbers.len());
Output-
Length of numbers is 5
SliceArray
Sleic the arrary by giving an expression the starting and ending index with double dots between. e.g.- [starting_index..ending_index]. Access the memory of the variable and provide the range e.g.- &array_variable[2..4]
Print the array and the slice using {:?}
Omit start index and end index [..4] and [2..] respectively
let numbers : [i32; 5] = [10, 20, 30, 40, 50];
let array_slice = &numbers[2..4];
let omit_start_index = &numbers[..4];
let omit_end_index = &numbers[2..];
println!("array = {:?}", numbers);
println!("slice = {:?}", array_slice);
println!("omit start index = {:?}", omit_start_index );
println!("omit end index = {:?}", omit_end_index );
let fruits = [["1", "2"],["apple", "orange"]];
println!("Selected fruit is - {}", fruits[1][1]);
Tuples
Tuples are similar to arrays except that tuples can have mixed data types. Similar to arrays tuples are stored in a fiexed-length and the data types must be know at compile time with elements are ordered.
Tuples is declared with comma seperated elements with round braces – (“hello”, 5 , ‘c’)
Here the first element is string then integer and character. See below example how to declare tuples and access elements.
Example-
// declare and inititaize tuple
let tuple = ("Hello", 5 , 's');
// Access elements
println!("First element in tupple is - {}",tuple.0)
Output-
First element in tupple is - Hello
Explict declaration can be done as follows-
Example-
// declare and inititaize tuple
let tuple: (&str, i32, char) = ("Hello", 5 , 's');
// Access elements
println!("First element in tupple is - {}",tuple.0)
// Prints "First element in tupple is Hello"
Updating element in tuple
First mark the variable as mutable. Access the element of the tuple and update.
// declare and inititaize tuple
let mut tuple: (&str, i32, char) = ("Hello", 5 , 's');
// Access second element and add 5
tuple.1 += 5;
// Print updated element
println!("Add 5 to second element in tupple - {}",tuple.1)
While updating the element be carefull that the element value does-not exceeds the max value a data type can hold or there will be memory overflow error.
Copy the tuple object
Continuing to the aboce code, decalre the tuple with 3 elements, assign the updated tuple and access the declared variable in tuple.
// declare and inititaize tuple
let mut tuple: (&str, i32, char) = ("Hello", 5 , 's');
// Access second element and add 5
tuple.1 += 5;
// Print updated element
println!("Add 5 to second element in tupple - {}",tuple.1);
let (first, second , third ) = tuple;
println!("Copied tuple third element is {}", third);
Output-
Add 5 to second element in tupple - 10
Copied tuple third element is s
Warnings-
Above code, first and second element are never used, hence the compiler will give warnings – unused variable:
Although it won’t stop the compiler from running the code. The suggestion here is to use prefix tuple element with _ (underscore) i.e. _first and _second. Lets change this and see if there are no warnings.
// declare and inititaize tuple
let mut tuple: (&str, i32, char) = ("Hello", 5 , 's');
// Access second element and add 5
tuple.1 += 5;
// Print updated element
println!("Add 5 to second element in tupple - {}",tuple.1);
let (_first, _second , _third ) = tuple;
println!("Copied tuple third element is {}", _third);
Now there are no warnings and compiles with results-
Variables must be explicitly declared as mutable using mut keyword
Rust is a statically typed language – all variable data types must be know at compile time.
Example-
//default immutable. value cannot be changed after declaration
let x = 10;
// marked as mutable. i.e value can be changed after declaration
let mut y = 20;
Compiler Errors-
let x = 10;
println!("x is {}", x);
x=20; // Error. Cannot be assigned twice. consider making this muttable
println!("x is {}", x);
Solution-
let mut x = 10; // make this mutable
println!("x is {}", x);
x=20; // compiles successfully
println!("x is {}", x);
Type of the varaible is declared after the : (colon)
Example:-
// signed 8-bit integer. max value can hold is 255
let x: i8 = 255;
let y: i8 = -10;
// unsigned 8-bit integer.
let z: u8 = 255;
Compiler Errors-
// unsigned 8-bit integer. max value 255
let z: u8 = 256;
Solution-
// unsigned 8-bit integer. max value 255
let z: u8 = 255; // compiles successfully
Runtime Errors-
// unsigned 8-bit integer. max value 255
let mut z: u8 = 255;
z = z + 1; // Error: panicked - attempt to add with overflow
println!("z is {}", z);
Solution-
// unsigned 8-bit integer. max value 255
let mut z: u8 = 254;
z = z + 1; // compiles and runs successfully
println!("z is {}", z);
Output- z is 255
Floating-Point Data Types
Represent numbers with decimal points
f32 and f64 are two floating-point types
Value stored as fractional and exponential components
f32- represents value from 6 to 9 decimal digits of precision.
f64- represents value from 15 to 17 decimal digits of precision.
Example-
let x= 10.00; // default is f64
println!("x is {} deafult type is f64", x);
let y: f32= 10.1234567890132456798; // default is f64
println!("y is {} with f32 floating-point type", y);
let z: f64= 10.1234567890132456798; // default is f64
println!("z is {} with f64 floating-point type", z);
Output-
x is 10 deafult type is f64
y is 10.123457 with f32 floating-point type
z is 10.123456789013245 with f64 floating-point type
Guidelines for Numeric data types–
Values with fractional component or decimal places use floating-point data type.
Use f64 or been dfault gived most precision range. With modern computers it is as good as using f32. So perrfomance should not be an issue.
Use f32 with embedded systems where memory is a limitation.
Default 32 signed integer (i32) provides a genrous range – between amd aroung plus or minus 2 billion
For memory concerns use smaller size integers to conserve and use less memory
Arithmetic Operations
Rust uses arithmetic operations with the operators +, -, *, / and %
Artihmentic operation results depend on the type of variables. example, if both operators are integer then will get result in integer
let x= 10; // default is i32
let y=3; // default is i32
let z= x / y;
println!("z is {}", z) // so z will be i32
Output- Here the value of z is 3 since both the variables are defaulted to signed integer i.e. i32
z is 3
Now if we add decimals to x and y the output is floating-point-
let x= 10.00; // default is f64
let y=3.00;
let z= x / y;
println!("z is {}", z)
Output- Here the default is f64.
z is 3.3333333333333335
Compiler Errors-
If one of the variables data type is different from other, then will receive error-
let x= 10; // default is i32
let y=3.00; // default is f64s
let z= x / y;
println!("z is {}", z)
Here the default integer is i32 and floating-point is f64. Dividing different data types will result in error. This is applicable for all artihmetice operations.
Solution-
For the above error cast the variable.
let x= 10; // default is i32
let y=3.00; // default is f64s
let z= x as f64 + y;
println!("z is {}", z)
Binary trait formats the output as a number in binary
Example-
let value= 0b11110101u8;
println!("value is {}", value)// Prints the number
println!("value is {:b}", value) // prints the binary
println!("value is {:010b}", value) // prints the binary upto 10 digits and preceding 0.
Output-
value is 245
value is 11110101
value is 0011110101
Here the binary is converted to number. The prefix 0b mentions the value is binary and suffix u8 converts the binary to unsigned integer.
Bitwise operations-
Logical operations on patterns using NOT, AND, OR, XOR and SHIFT.
Taking the above example, Bitwise NOT-
let mut value= 0b11110101u8;
value=!value;
println!("value is {:08b}", value); // prints the negated binary
Output-
value is 00001010
Bitwise AND- change the value of a specific Bit-
Use the & with the anotehr binary to change the value.
Example- to change the value of the highlighted 11110111 to 0, & this with 11110011. Ouput will be 11110011
Example-
let mut value= 0b11110111u8;
value=value & 0b11110011;
println!("value is {:08b}", value);
Output-
value is 11110011
Likewise use | (pipe) for OR, ^ for XOR, << Left shift and >> Right Shift
Boolean data types and operations
Use the above operatos used in bitwise for boolean operations.
Example-
let a = true;
let b= false;
println!("a is {} and b is {}", a, b);
println!("NOT a is {} ", !a);
println!("a AND b is {} ", a & b);
println!("a OR b is {} ", a | b);
println!("a XOR b is {} ", a ^ b);
Output-
a is true and b is false
NOT a is false
a AND b is false
a OR b is true
a XOR b is true
Short-Circuiting Logical Operations
With this in OR operation if the left side is True then it won’t check the right side since the result for OR will be always true.
Similarly, for AND operation if the left side is False, it won’t check the value at the right side, since the result will be always False.
This can be done using && or ||. This improves the code effeciency.
Example-
let a = true;
let b= false;
let c= (a ^ b) || (a & b);
println!("c is {}", c);
Use compareision operators to compare values. Some of these are-
Equal ==
Not Equal !=
Greater Than >
Less Than <
Greater Than Equal >=
Less Than Equal <=
Example-
let a = 1;
let b= 2;
println!("a is {} and b is {}", a, b);
println!("a EQUAL TO b is {} ", a == b);
println!("a NOT EQUAL TO b is {} ", a != b);
println!("a GREATER THAN TO b is {} ", a > b);
println!("a LESS THAN TO b is {} ", a < b);
println!("a GREATER THAN EQUAL TO b is {} ", a >= b);
println!("a LESS THAN EQUAL TO b is {} ", a <= b);
Output-
a is 1 and b is 2
a EQUAL TO b is false
a NOT EQUAL TO b is true
a GREATER THAN TO b is false
a LESS THAN TO b is true
a GREATER THAN EQUAL TO b is false
a LESS THAN EQUAL TO b is true
The comparision can be used with the similar data types.
Char Data Type
Represents a single character
Stored using 4 bytes
Unicode scalar value
Char can be represented within a single quote e.g.- ‘a’
Unicode characters can be represented using “\u{hexa decimal value}”
let letter = 'a';
let number = '1';
let unicode= '\u{0024}';
println!("Letter is {}", letter);
println!("Number is {}", number);
println!("Unicode is {}", unicode);
There are various ways you should be able to do this. I am adding 5 times more space to the existing indent-top style.
_indent.scss
// $middle-margin is defined in _margins.scss
.indent-large-top {
margin-top: calc($middle-margin * 5);
}
Apply a custom style to rendering
Select the component or container you want to apply style and choose option “Indent Large Top” in Spacing section
Now the space between the 2 component is increased and is 100px as per the requirement.
New style applied to container-
Apply style to specific renderings
As above when the style was created it was applied to all renderings.
If you want to restrict the style to be applied to only certain renderings you can do so by setting Allowed renderings field in new created Style item.
For “Indent Large Top” only SectionContainer will be able to see the new Spacing Style.
In Experience Editor you wont see the “Indent Large Top” for other renderings e.g.- for container rendering-
While for Section Container rendering the new style is available-
For Noncustodial wallets keep your recovery code safe
Don’t fall in trap if wallet application asks for recovery code for no reason – Recovery code is asked while creating a wallet i.e. initial setup or if you have lost your wallet i.e. recovery – other than that ensure that you are been not phished
Don’t keep all you crypto assets in a single address –
Don’t share the same address to multiple person – Private keys are used to generate the Bitcoin Address. For each transaction create a new address. This way you avoid anybody to know how much bitcoin has been sent to that address in total. Generating new address everytime also protects your privacy.
Block explorer privacy – Block explorer is a web appplication that operates as a Bitcoin search engine. You can search by Bitcoin addresse, transaction hash, block number and block hash. Using these applications and searching a transaction allows them to associate the IP address, previous earches and browser details through which can identify and learn your activities. Searching somebody else transaction should not be a problem but if you search your own transactions these operators might be able to analyse the Bitcoin your have received and spent or currently own. So as mentioned earleir each transaction should be on different address to make the operators difficult to identify you.
Ways to acquire a Bitcoin as a new user
Bitcoin transactions are irreversible. So be careful when doing transaction either send or receive. Since the transactions are done on address and there is not identity attached, there is no verification process to check if the address is your’s before doing a transaction. This way acquring, holding and spending bitcoin does not expose your personal identity. Although everybody in the network can see the how much bitcoin is in a address but that address doesn’t disclose your identity. As a new user follow this guidelines-
First do a self study how the crypto transaction works. With most of the mobile apps its as as easy as transfering the fiat currency. But if you have a self custodial assets its very important to understand the process. Understand the current Price of bitcoin from the currency exchange, transaction fees, location from where you will be doing transactions. It is good to understand the rules and regulations of the country where you reside.
Get introduction about bitcoin from a friend – Take help from you friend who already has Bitcoin and buy from your them directly with a small amount. This should give you a confidence when doing further transactions by yourself. Once you are familiarised and have confidently done transactions help new users and share your expereince.
Earn a bitcoin. Earn a bitcoin by providing service with which ever profession you are in. Example- if you are porgrammer you sell your skills for firat currency, instead sell your service for bitcoin. This requires to share your adddress along with the invoice to your client who should then send agreed bitcoin to your address. This way you learn how to generate address to receive bitcoin. Always remember to genereate new address for each invoice. See section “Don’t share the same address to multiple person“.
Use Bitcoin ATM – A Bitcoin ATM is a standalone device or kiosk that allows you to buy or sell bitcoin or other cryptocurrencies using a terminal. Bitcoin ATMs are connected to the Internet and often utilize QR codes to send and receive tokens to users’ digital wallets. Bitcoin ATM accepts cash and send bitcoins to your wallet. This way you get to familiarise with bitcoin transaction’s.
Use Bitcoin currency eschange – you can buy bitcoin from the digital curerncy exchange such as Coinbase which is linked to your back account. Although they will take the transaction fees but a safe way to buy or sell the bitcoins.
Generating Private Key
Do not write your own code to create a random number or use a simple random number generator offered by programming language. Use CSPRNG (crytpographically secure pseudorandom number generator) with a seed from a source of sufficient entropy. What is entropy – see here blog post of private key
