Quasiquotation in python
Blocks of non-python code sprinkled in for extra seasoning.
What is a quasiquote
An quasiquote is a new syntactical element that allows us to embed non python code into our existing python code. The basic structure is as follows:
# coding: quasiquote [$name|some code goes here|]
This desuagars to:
name("some code goes here")
This allows us to use slightly nicer syntax for our code. The # coding: quasiquote is needed to enable this extension. The syntax is chosen to match haskell’s quasiquote syntax from GHC 6.12. We need to use the older syntax (with the $) because python’s grammar would be ambiguous without it at the quote open step. To simplify the tokenizer, we chose to use slighly more verbose syntax.
We may also use statement syntax for quasiquotes with a modified with block:
with $name: some code goes here
This desugars the same as the block above.
The c quasiquoter
The builtin c quasiquoter allows us to inline C code into our python. For example:
>>> def f(a): ... with $c: ... printf("%ld\n", PyLong_AsLong(a)); ... a = Py_None; ... Py_INCREF(a); ... print(a) ... >>> f(0) 0 None >>> f(1) 1 None
Here we can see that the quasiquoter can read from and write to the local scope.