Steven Schveighoffer:
> lol!!!
I know, I know... :-) But when people do errors so often, the error is
elsewhere, in the original choice of that word to denote how many items an
iterable has.
In my libs I have defined len() like this, that I use now and then (where
running speed isn't essential):
long len(TyItems)(TyItems items) {
static if (HasLength!(TyItems))
return items.length;
else {
long len;
// this generates: foreach (p1, p2, p3; items) len++; with a variable
number of p1, p2...
mixin("foreach (" ~ SeriesGen1!("p", ", ", OpApplyCount!(TyItems), 1) ~
"; items) len++;");
return len;
}
} // End of len(items)
/// ditto
long len(TyItems, TyFun)(TyItems items, TyFun pred) {
static assert(IsCallable!(TyFun), "len(): predicate must be a callable");
long len;
static if (IsAA!(TyItems)) {
foreach (key, val; items)
if (pred(key, val))
len++;
} else static if (is(typeof(TyItems.opApply))) {
mixin("foreach (" ~ SeriesGen1!("p", ", ", OpApplyCount!(TyItems), 1) ~
"; items)
if (pred(" ~ SeriesGen1!("p", ", ", OpApplyCount!(TyItems), 1) ~ "))
len++;");
} else {
foreach (el; items)
if (pred(el))
len++;
}
return len;
} // End of len(items, pred)
alias len!(string) strLen; /// ditto
alias len!(int[]) intLen; /// ditto
alias len!(float[]) floatLen; /// ditto
Having a global callable like len() instead of an attribute is (sometimes)
better, because you can use it for example like this (this is working syntax of
my dlibs):
children.sort(&len!(string));
That sorts the array of strings "children" according to the given callable key,
that is the len of the strings.
Bye,
bearophile
