And the Haskell example doesn't even include common operators like <$> or <*> or <>. I would've also expected some fancier arrows like =<< or >>>.

if you're looking for those Haskell operators, you'd find them in the huge banner at the start. maybe i should also add them in the illustrations too.

That unfortunately doesn't show them in context.

agreed. formulae are essential LaTeX. are there any particular glyphs compositions which you'd suggest?

Thanks! For something more complex, I suggest a moderately complex formula with parentheses and superscripts like $f \in \mathcal{C}^0([a,b])$, an equation delimited by \[...\], and maybe a macro declaration with parameters like \newcommand\halves[1]{\frac{#1}{2}}.