The Expander

The Qi expander is implemented with Syntax Spec. See Source Code Overview to find the implementation in the codebase.

The expander expands Qi surface syntax (including macros) to the Qi core language. This core language is then compiled to Racket.

To see what a Qi expression expands to, you could use the expand-flow compile-time function to expand expressions on demand. This function expects to be called during macroexpansion, so you can use the phase1-eval utility from the syntax/macro-testing collection to do that. For example:

(require qi
         (submod qi/flow/extended/expander invoke)
         syntax/macro-testing)

(phase1-eval
 (expand-flow #'(~>> (filter odd?) (map sqr))))

which produces:

'(thread
  (#%blanket-template ((#%host-expression filter) (#%host-expression odd?) __))
  (#%blanket-template ((#%host-expression map) (#%host-expression sqr) __)))