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m.entrySet().removeIf(e -> !p.test(e));for (auto it = m.begin(); it != m.end();) {
if (!p(it->second)) {
it = m.erase(it);
} else {
++it;
}
}Filters in place.
m.Where(p);returns a new IEnumerable.
real, dimension(:), allocatable :: a
a = pack(a,p(a))
!
elemental logical function p(x)
real, intent(in) :: x
p = x > 0.7
end function p
p(a) is an elemental function returning a LOGICAL value
$p = sub { $_[0] };
while ( ($k,$v) = each %m ) {
$f{$k} = $v if $p->($v);
}
%m = %f;$p is an anonymous function that (in this example) simply returns the argument it is passed, which is then taken for its boolean value. It could, of course, be much more complex.
The while loop extracts the keys and values from the map (hash, in perl lingo) and creates a new hash %f whenever the value satisfies the predicate function. (Deleting keys during iteration is unpredictable so we use a second hash). When done, we assign the new hash to the old one.
The while loop extracts the keys and values from the map (hash, in perl lingo) and creates a new hash %f whenever the value satisfies the predicate function. (Deleting keys during iteration is unpredictable so we use a second hash). When done, we assign the new hash to the old one.
$p = sub { $_[0] };
foreach $k (keys %m) {
delete $m{$k} if not $p->( $m{$k} );
}
$p is an anonymous function that simply returns the value of its argument, which is expected to be interpreted as a boolean. It could be more complex.
The foreach loop iterates over the keys of the map (or hash, in perl parlance) and the code block deletes entries that return false if the predicate function returns false given the entry value.
The foreach loop iterates over the keys of the map (or hash, in perl parlance) and the code block deletes entries that return false if the predicate function returns false given the entry value.
m = dict(filter(p, m.items()))for k in list(m):
if p(m[k]): m.pop(k)
Modifies m in-place, but creates a temporary list of all the keys.
m = {k:v for k, v in m.items() if p(v)}Creates a new map.
m.select{|k,v| p(v) }select! (with an exclamation mark) would modify in-place
m.retain(|_, &mut v| p(v));Filtering on values happens in place.
The keys are ignored.
The keys are ignored.