Interesting, so if you’re using a lazy language then you don’t need a macro here and could write my-unless as a function.
https://dlang.org/articles/lazy-evaluation.html
It makes it hard to know when things run. In Lisp you also have that problem everywhere, of course.
As the post shows this allows you to do stuff that looks like extending the syntax of the language.
I can’t decide if I love it or hate it!
Worth mentioning in Elisp that even if you don't define your own macros, you use them more often than you would think. defun, unless, def-custom, etc (more examples in the blog post) are all macros. The fact they look and feel like non-macros like special forms and built in functions implemented in C is part of what makes elisp so cool to me. There are plenty of homoiconic languages, but you rarely feel the distinction between program and data in elisp, and macro-supporting lisps in general.
Furthermore, macros and functions constitute a kind of function coloring. To use a macro in a function, like defcustom, you couldn't pass the name of the user option you are defining in as a symbol, as that is not evaluated. So instead you'd have to call eval on a runtime constructed expression, which is a cludge.
So I agree with the top comment, to avoid macros is a sign of Lisp maturity. It is easy and fun to admire them when you are coming from languages with arbitrary restrictions in their macro systems like C, but ones you get used to them you don't treat them with any more wonder than any other arbitrary restriction that a language may lack (bad ad hoc example: nobody praises C for the lack of a CALL keyword).
And apparently neither Penrose nor Escher knew about Oscar Reutersvärd's work! Oscar got robbed lol.
lexilambda created Typed Racket on top of Racket. https://github.com/racket/typed-racket