[ModernMech]

Indeed, these languages are descendants of ISWIM by Peter Landin.

ISWIM also inspired Lucid, so I guess PyFL would be a nephew of SASL in that case.

[tgv]

ISWIM isn't lazy, I think, nor fully functional.

[ModernMech]

Right, but it’s still the root of the functional branch of the PL family tree. ISWIM to ML is mostly a matter of removing the few imperative features from ISWIM. Once you do that, lazy execution comes naturally.