Variance in programming languages

Covariance, invariance, and contravariance are concepts many students have difficulties to grasp. However, the idea behind them is pretty simple. This post will attempt to illustrate that in a shortest and simplest way possible.

I have recently switched to Spacemacs with markdown-mode to write everything markdown-related, especially making notes for whatever things I am fiddling with. While ‘markdown-mode’ is amazing, there is one feature I miss, that is: ‘pasting’ a part of a screenshot into a markdown file by saving it somewhere and generating a correct link. It is a huge waste of time and concentration to do it by hand.