[bug] index-operators fail if not int

[ClmnsRck]

When doing something like this:

for(long i = 0; i < SIZE; ++i){
    array(i,0) = 1;
}

It fails, as long does not seem supported ... neither is size_t nor uint64_t.

[ClmnsRck]

either i am really lucky while doing something forbidden, or there is something wrong, as not even uint32_t is supported

[AnderOne]

See #111 (comment)