Expand description
Loop while a condition is upheld.
A while
expression is used for predicate loops. The while
expression runs the conditional
expression before running the loop body, then runs the loop body if the conditional
expression evaluates to true
, or exits the loop otherwise.
let mut counter = 0;
while counter < 10 {
println!("{}", counter);
counter += 1;
}
RunLike the for
expression, we can use break
and continue
. A while
expression
cannot break with a value and always evaluates to ()
unlike loop
.
let mut i = 1;
while i < 100 {
i *= 2;
if i == 64 {
break; // Exit when `i` is 64.
}
}
RunAs if
expressions have their pattern matching variant in if let
, so too do while
expressions with while let
. The while let
expression matches the pattern against the
expression, then runs the loop body if pattern matching succeeds, or exits the loop otherwise.
We can use break
and continue
in while let
expressions just like in while
.
let mut counter = Some(0);
while let Some(i) = counter {
if i == 10 {
counter = None;
} else {
println!("{}", i);
counter = Some (i + 1);
}
}
RunFor more information on while
and loops in general, see the reference.