[zabzonk]

using recursive descent, you don't need to build an ast

[jjtheblunt]

the call stack during recursive descent is an ephemeral ast, for the recursive descent parsers I've written.

[hedora]

That implies the memory usage is proportional to the depth of the AST, not the total size (which is the point, I think).

[pjmlp]

Only if the compiler doesn't do anything beyond basic peephole optimizations.