keys - return an array of the keys from the (key, value) pairs in a mapping

array keys( mapping m );

keys() returns an array of keys (indices) corresponding to the keys in
the (key, value) pairs stored in the mapping m.

For example, if:

<pre>
mapping m;
m = (["hp" : 35, "sp" : 42, "mass" : 100]);
</pre>

then

<pre>
keys(m) == ({"hp", "sp", "mass"})
</pre>

Note: the keys will not be returned in any apparent order.  However, they
will be returned in the same order as the corresponding values (returned
by the values() efun).

See also:
 values