How To Make a For Loop and Range in Rust

Created Apr 23, 2022 at 10:44

Modified Apr 23, 2022 at 10:49

Using while Expression

A while loop begins by evaluating the boolean loop conditional operand.

fn main() {
  let mut i = 0;
  while i < 3 {
    println!("{}", i);
    i += 1;
  }
  // Vec
  let mut x = vec![1, 2, 3];
  while let Some(y) = x.pop() {
    println!("{}", y)
  }
  // Empty
  // warning: irrefutable `while let` pattern
  while let _ = 5 {
    // do Something
    break;
  }
}

Using for Pattern in Expression

A for expression is a syntactic construct for looping over elements provided by an implementation of std::iter::IntoIterator. For example,

fn main() {
  let v = &["Apple", "Google"];
  for text in v {
    println!("{}", text)
  }

  // a series of integers
  for i in 1..3 {
    println!("{}", i)
  }
}

Apple
Google
1
2

Using loop Expression

A loop expression denotes an infinite loop. For example,

fn main() {
  // loop expression
  loop {
    println!("Infinite loops");

    break;
  }

  // Result
  let mut i = 0;
  let result = loop {
    if i >= 3 {
      break i;
    }
    i += 1;
    println!("Infinite");
  };
  println!("{}", result);
}

Infinite loops
Infinite
Infinite
Infinite
3

Range expressions

Examples:

fn main() {
  // Range expressions
  // 1..2; // std::ops::Range
  // 3..; // std::ops::RangeFrom
  // ..4; // std::ops::RangeTo
  // ..; // std::ops::RangeFull
  // 5..=6; // std::ops::RangeInclusive
  // ..=7; // std::ops::RangeToInclusive

  let x = std::ops::Range { start: 0, end: 2 };
  let y = 0..2;
  for i in y {
    println!("{}", i)
  }
}

0
1

The .. and ..= operators will construct an object of one of the std::ops::Range (or core::ops::Range) variants, according to the following table:

Syntaxstart..end
std::ops::Range start ≤ x < end
start..
std::ops::RangeFrom  start ≤ x
..end
std::ops::RangeTo  x < end
..
std::ops::RangeFull -
start..=end
std::ops::RangeInclusive start ≤ x ≤ end
..=end
std::ops::RangeToInclusive  x ≤ end