Declarative macros for common control-flow use cases such as break, continue, and return.
Break from a loop if a given predicate evaluates to true.
use flow_control::break_if;
break_if!(predicate);
break_if!(predicate, label);Continue to the next iteration of a loop if a given predicate evaluates to true.
use flow_control::continue_if;
continue_if!(predicate);
continue_if!(predicate, label);Return from a function if a given predicate evaluates to true.
use flow_control::return_if;
return_if!(predicate);
return_if!(predicate, value);use flow_control::break_if;
let mut v = Vec::new();
for outer_n in 1..3 {
for inner_n in 1..5 {
break_if!(inner_n == 3);
v.push((outer_n, inner_n));
}
}
assert_eq!(
v,
vec![
(1, 1), (1, 2),
(2, 1), (2, 2),
]
);use flow_control::break_if;
let mut v = Vec::new();
'outer: for outer_n in 1..3 {
for inner_n in 1..5 {
break_if!(inner_n == 3, 'outer);
v.push((outer_n, inner_n));
}
}
assert_eq!(
v,
vec![(1, 1), (1, 2)],
);use flow_control::continue_if;
let mut v = Vec::new();
for outer_n in 1..3 {
for inner_n in 1..5 {
continue_if!(inner_n == 3);
v.push((outer_n, inner_n));
}
}
assert_eq!(
v,
vec![
(1, 1), (1, 2), (1, 4),
(2, 1), (2, 2), (2, 4),
]
);use flow_control::continue_if;
let mut v = Vec::new();
'outer: for outer_n in 1..3 {
for inner_n in 1..5 {
continue_if!(inner_n == 3, 'outer);
v.push((outer_n, inner_n));
}
}
assert_eq!(
v,
vec![
(1, 1), (1, 2),
(2, 1), (2, 2),
]
);use flow_control::return_if;
let mut v = Vec::new();
(|| {
for n in 1..10 {
return_if!(n == 5);
v.push(n)
}
})();
assert_eq!(v, vec![1, 2, 3, 4]);use flow_control::return_if;
let get_value = || {
for n in 1..10 {
return_if!(n == 5, "early return");
}
return "return after loop";
};
assert_eq!(get_value(), "early return");