I see $ used in various places in the MiniZinc Handbook (mostly in the Reference Manual portion), but I haven't been able to find a definition. Would someone kindly explain it to me. Thanks.
MiniZinc supports three basic types, {int, float, bool }. The documentation uses $T as a place-holder for any type contained in this set, so that it is not necessary to provide three versions of each function's signature, one for each basic type.
I guess that this syntax style is inspired by the shell, where the notation $T is used to dereference the name T and it normally yields the value corresponding to such name/memory location.
One can also think as $T as a template typename/class in the C++ language, that achieves the exact same purpose.
// MiniZinc Docs
set of $U: array_union(array[$T] of set of $U)
// C++-like style
template <class T, class U>
set<U> array_union(map< T, set<U> >);