rust programming language
Learn from examples
1. Program to declare and print integer, double, and string
exru1.ru source code
// exru1.ru declare and print integer, double, string
fn main()
{
let i = 7; // immutable can not be changed
let x = 3.5;
let name = "some name";
let yes = true;
let no = false;
let mut y = 4.0; // mut needed if going to change
y = y + 0.5;
// Print text to the console
println!("exru1.ru running");
println!("i= {:?} ",i);
println!("x= {:?}",x);
println!("name= {:?}",name);
println!("yes= {:?}",yes);
println!("no= {:?}",no);
println!("y= {:?}",y);
println!("types are i32 i64 f32 f64 boolean ... ");
println!(" ");
println!("exru1.ru finished");
}
Output from execution:
exru1.ru running
i= 7
x= 3.5
name= "some name"
yes= true
no= false
y= 4.5
types are i32 i64 f32 f64 boolean ...
exru1.ru finished
get_type.ru source code
// get_type.ru
use std::any::type_name;
fn type_of(_: T) -> &'static str {
type_name::()
}
fn main() {
println!("get_type.ru running");
println!(" ");
let j = 21;
let i:i64 = 10;
let k:i32 = 9;
let y = 2.5;
let x:f32 = 6.0;
let name = "mine";
let yes = true;
let n = 10;
let mut _a = vec![0.0_f64; n];
let mut _b = vec![vec![0.0_f64; n]; n];
println!("j {}", type_of(j));
println!("i {}", type_of(i));
println!("k {}", type_of(k));
println!("y {}", type_of(y));
println!("x {}", type_of(x));
println!("name {}", type_of(name));
println!("yes {}", type_of(yes));
println!("n {}", type_of(n));
println!("_a {}", type_of(_a));
println!("_b {}", type_of(_b));
println!(" ");
println!("get_type.ru finished");
}
Execution output
get_type.ru running
j i32
i i64
k i32
y f64
x f32
name &str
yes bool
n usize
_a alloc::vec::Vec
_b alloc::vec::Vec>
get_type.ru finished
2. commands to execute the source code
at a minimum, Windows, Linux, MacOSX.
Windows: optional write output to file
rustc exru1.ru
exru1 exru1 > exru1_ru.out
Linux:
rustc exru1.ru
./exru1 ./exru1 > exru1_ru.out
MacOSX
rustc exru1.ru
exru1
3. You must be able to declare variables and arrays
and matrix of various types.
exru3.ru source code
// exru3.ru declare and use vector and matrix
fn main()
{
println!("exru3.ru running");
let mut xs = vec![0, 1, 2];
println!("Initial xs= {:?}", xs);
// Insert new element at the end of the vector
println!("Push 3 onto xs");
xs.push(3);
println!("longer xs= {:?}", xs);
println!("xs length= {}", xs.len());
println!("xs[2]= {}", xs[2]);
println!("Pop last element of xs= {:?}", xs.pop());
println!("xs length= {}", xs.len());
let n = 3;
let mut _xt = vec![0.0_f64; n];
println!("Initial xt= {:?}", _xt);
println!("xt length= {}", _xt.len());
_xt[1] = 1.1;
_xt[2] = 2.2;
println!("updated xt= {:?}", _xt);
let mut _a = vec![vec![0.0_f64; n]; n];
println!("initial a= {:?}", _a);
_a[0][0] = 1.0;
_a[1][1] = 1.0;
_a[2][2] = 1.0;
println!("updated a= {:?}", _a);
let mut _b = vec![vec![0.0_f64; n]; n];
_b[0][0] = 2.0;
_b[1][1] = 2.0;
_b[2][2] = 2.0;
println!("updated b= {:?}", _b);
let mut _c = vec![vec![0.0_f64; n]; n];
for j in 0..n { // matrix multiply
for i in 0..n {
for k in 0..n {
_c[i][j] += _a[i][k] * _b[k][j];
}
}
}
println!("c=a*b= {:?}", _c);
println!("exru3.ru finished");
}
Execution output:
exru3.ru running
Initial xs= [0, 1, 2]
Push 3 onto xs
longer xs= [0, 1, 2, 3]
xs length= 4
xs[2]= 2
Pop last element of xs= Some(3)
xs length= 3
Initial xt= [0.0, 0.0, 0.0]
xt length= 3
updated xt= [0.0, 1.1, 2.2]
initial a= [[0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [0.0, 0.0, 0.0]]
updated a= [[1.0, 0.0, 0.0], [0.0, 1.0, 0.0], [0.0, 0.0, 1.0]]
updated b= [[2.0, 0.0, 0.0], [0.0, 2.0, 0.0], [0.0, 0.0, 2.0]]
c=a*b= [[2.0, 0.0, 0.0], [0.0, 2.0, 0.0], [0.0, 0.0, 2.0]]
exru3.ru finished
4. You need to be able to have loops, iteration statements
exru4.ru source code
// exru4.ru loops iteration for while
fn main()
{
println!("exru4.ru running");
for i in 0..5
{
println!("i= {:?} ",i);
}
println!(" ");
for j in 1..10
{
if j==3
{
continue; // skip 3
}
else if j>7
{
break; // no 8,9,10
}
println!("j= {:?} ",j);
}
println!(" ");
let mut x = 4.0;
while x >= 1.0
{
println!("x= {:?}",x);
x = x - 1.0;
}
println!(" ");
println!("exru4.ru finished");
}
Execution output:
exru4.ru running
i= 0
i= 1
i= 2
i= 3
i= 4
j= 1
j= 2
j= 4
j= 5
j= 6
j= 7
x= 4.0
x= 3.0
x= 2.0
x= 1.0
exru4.ru finished
5. You need if else conditional statements
exru5.ru source code
// exru5.ru if else
fn main()
{
println!("exru5.ru running");
let mut j = 3;
if j > 2 && j < 5
{
println!("j= {:?} ",j);
}
let mut x = 1.0;
if x <= 2.0 || x >= 4.0
{
println!("x= {:?} ",x);
}
j = 5;
x = 4.5;
if j == 3
{
println!("j= {:?} ",j);
}
else if x!= 4.5
{
println!("x= {:?} ",x);
}
else
{
println!("else");
}
println!("exru5.ru finished");
}
Execution output:
exru5.ru running
j= 3
x= 1.0
else
exru5.ru finished
6. You need to be able to create functions, procedures,
subroutines.
exru6.ru source code
// exru6.ru create and use functions and procedures
fn factorial(i: u64) -> u64 {
match i {
0 => 1,
n => n * factorial(n-1)
}
} // end factorial
fn sort(n:usize, mut _a:Vec) -> Vec
{
println!("sort n= {:?}",n);
println!("a= {:?}",_a);
let mut b = vec![0.0_f64; n];
for i in 0..n
{
b[i] = _a[i];
}
for i in 0..(n-1)
{
let mut k = i;
for j in (i+1)..n
{
if b[j] < b[k]
{
k = j;
}
if k != i
{
let t = b[i];
b[i] = b[k];
b[k] = t;
}
}
}
return b;
} // end sort
fn main()
{
println!("exru6.ru running");
let result = factorial(10);
println!("factorial(10)= {}",result);
let n = 10;
let mut x = vec![0.0_f64; n];
let mut xs = vec![0.0_f64; n];
println!("sort vector of double, n= {}", n);
for i in 0..n
{
x[i] = (n as f64)-(i as f64);
print!("x[{}",i);
println!("]= {:?}", x[i]);
}
xs = sort(n,x);
println!("result vector");
for i in 0..n
{
print!("xs[{}",i);
println!("]= {:?}", xs[i]);
}
println!(" ");
println!("exru6.ru finished");
}
Execution output:
exru6.ru running
factorial(10)= 3628800
sort vector of double, n= 10
x[0]= 10.0
x[1]= 9.0
x[2]= 8.0
x[3]= 7.0
x[4]= 6.0
x[5]= 5.0
x[6]= 4.0
x[7]= 3.0
x[8]= 2.0
x[9]= 1.0
sort n= 10
a= [10.0, 9.0, 8.0, 7.0, 6.0, 5.0, 4.0, 3.0, 2.0, 1.0]
result vector
xs[0]= 1.0
xs[1]= 2.0
xs[2]= 3.0
xs[3]= 4.0
xs[4]= 5.0
xs[5]= 6.0
xs[6]= 7.0
xs[7]= 8.0
xs[8]= 9.0
xs[9]= 10.0
exru6.ru finished
7. You need to be able to read and write files in various formats.
exru7.ru source code
// exru7.ru write and read text files
use std::io::Write; // for write
use std::io::Read; // for first read
use std::fs; // for second read
fn main() // write 3 lines to out.txt, then read out.txt
{
println!("exru7.ru running");
// write 3 lines to out.txt
let mut file_ref = std::fs::File::create("out.txt").expect("create failed");
file_ref.write_all("Hello World\n".as_bytes()).expect("write failed");
file_ref.write_all("Hello India\n".as_bytes()).expect("write failed");
file_ref.write_all("last line 3\n".as_bytes()).expect("write failed");
println!("Text written into file out.txt");
// first read out.txt
let mut file_ref = std::fs::File::open("out.txt").unwrap();
let mut data = String::new();
file_ref.read_to_string(&mut data).unwrap();
println!("read data= {:?}",data);
// second read out.txt
let file_name = "out.txt";
let file_content = fs::read_to_string(file_name)
.expect("Failed to read the file");
println!("from second read: ");
println!("out.txt= {:?}",file_content);
println!(" ");
println!("\nFile contents:\n-----------\n{}\n", file_content);
println!("exru7.ru finished");
}
Execution output:
exru7.ru running
Text written into file out.txt
read data= "Hello World\nHello India\nlast line 3\n"
from second read:
out.txt= "Hello World\nHello India\nlast line 3\n"
File contents:
-----------
Hello World
Hello India
last line 3
exru7.ru finished
8. You need to be able to use a number of files combined to
build a program. This may include packages, libraries,
operating system commands, header files, etc.
exru8.ru source code
Execution output:
Other sample source code and output
sin, cos, ..., exp, log, min, max
import 'rust:math';
trig.ru source code
trig_ru.out output
test_string.ru source code
test_string_ru.out output
factorial.ru source code
factorial_ru.out output
Last updated 2/14/2022