[ironix]

Interesting, though I must ask: Why YML instead of a DSL?

Granted, I come from Ruby, and writing DSLs is pretty typical. Maybe not so popular in Python.

I am asking this because I become suspicious of config languages that read like code. Is not a bonafide programming language the better choice in this scenario? i.e. all overly-configurable formats (e.g. Terraform .tf files, JSON schemas...) converge on just being a new scripting language?

[logv]

good point! i'm not against a DSL. as I was working on plait.py, one thought going through my head was: "am i re-writing haskell or lisp but worse"? my experience with python and DSL is that I need to use YACC / PLY to create a grammar and so on. maybe a lot of work. i take it that its easier in ruby?

yaml was a format I chose because it is easy to write (close to human), but can not express full programming concepts (but yes to some metaprogramming). i did not want the templates to be full powered as they are meant to be able to express relationships between variables, but not much more (especially not side effects). they also support lazy evaluation - statements do not need to be in order. this is closer to a "mathematical language" for me.

the choice for yaml was also based on the premise that if performance becomes an issue, can hopefully move to another language but retain templates (will have to re-implement python's "random" compat, though)