Yep, I've been writing it that way forever, it just tends to get autocorrected.

> In informal contexts, a hyphen-minus (-) is often used as a substitute for an en dash, as is a pair of hyphen-minuses (--) for an em dash, because the hyphen-minus symbol is readily available on most keyboards. The autocorrection facility of word-processing software often corrects these to the typographically correct form of dash. - https://en.wikipedia.org/wiki/Dash