I am trying to understand the syntax of .bst-files using the Guide Tame the Beast. For starters, I want to understand the example of the multiplication function on page 39 (The functions skip$ and if$ are explained on pages 33 to 35):
The first assignment in the function looks like this:
Which is described as "We store the first value".
I know about stack-oriented programming and reverse polish notation, but I never actually coded it myself. What does the apostrophe do here? Is it related to "storing"? Sometomes I also see functions (such as skip$) with a preceding apostrophe. What is the meaning of this?