Rust Tutorial : Slices
from tutorialspoint.com

Slicing
What is a slice?
a slice is a pointer to a block of memory
slices can be used to access portions of data stored in contiguous memory blocks
it can be used with data structures like arrays, vectors and strings
slices use index numbers to access portions of data
the size of a slice is determined at runtime

slices are pointers to the actual data
they are passed by reference to functions, which is also known as borrowing
syntax 

let sliced_value = &data_structure[start_index..end_index]
the minimum index value is 0 and the maximum index value is the size of the data structure
the end_index will not be included in final string

Slicing a string
example fetches 5 characters from the string (starting from index 4) 
fn main() {
   let n1 = "Tutorials".to_string();
   println!("length of string is {}",n1.len());
   let c1 = &n1[4..9]; 
   
   // fetches characters at 4,5,6,7, and 8 indexes
   println!("{}",c1);
}
output 
length of string is 9
rials
Slicing an integer array
the main() function declares an array with 5 elements
it invokes the use_slice() function and passes to it a slice of three elements (points to the data array)
the slice is passed by reference
the use_slice() function prints the value of the slice and its length 
n main(){
   let data = [10,20,30,40,50];
   use_slice(&data[1..4]); // this is effectively borrowing elements for a while
}
fn use_slice(slice:&[i32]) { 
   // is taking a slice or borrowing a part of an array of i32s
   println!("length of slice is {:?}",slice.len());
   println!("{:?}",slice);
}
output 
length of slice is 3
[20, 30, 40]
Mutable Slices
the &mut keyword can be used to mark a slice as mutable
code passes a mutable slice to the use_slice() function
the function modifies the second element of the original array 
fn main(){
   let mut data = [10,20,30,40,50];
   use_slice(&mut data[1..4]);
   // passes references of 
   20, 30 and 40
   println!("{:?}",data);
}
fn use_slice(slice:&mut [i32]) {
   println!("length of slice is {:?}",slice.len());
   println!("{:?}",slice);
   slice[0] = 1010; // replaces 20 with 1010
}
output 
length of slice is 3
[20, 30, 40]
[10, 1010, 30, 40, 50]
index