Abstract syntax tree and pretty-printing for Python. Works for Python 2 and 3. A lot of the data structures are inspired by the language-python package; I have chosen not to have language-python as a dependency of sifflet-lib, however, because it would be overkill and still allows to little control over pretty-printing of Python expressionsw.
- class PyPretty a where
- data PModule = PModule [PStatement]
- data PStatement
- alterParens :: (Expr -> Expr) -> PStatement -> PStatement
- ret :: Expr -> PStatement
- condS :: Expr -> Expr -> Expr -> PStatement
- var :: String -> Expr
- ident :: String -> Symbol
- char :: Char -> Expr
- fun :: String -> [String] -> Expr -> PStatement
- operatorTable :: Map String Operator
Expr as an instance of PyPretty. This instance is only for Exprs as Python exprs, for export to Python! It will conflict with the one in ToHaskell.hs (or Haskell.hs).
The EOp case needs work to deal with precedences and avoid unnecessary parens. Note that this instance declaration is for *Python* Exprs. Haskell Exprs of course should not be pretty-printed the same way!
Python module -- essentially a list of statements; should it also have a name?
|PCondS Expr PStatement PStatement|
if condition action alt-action
|PFun Symbol [Symbol] PStatement|
function name, formal parameters, body
Binary operators Precedence levels are rather *informally* described in The Python Language Reference, http:docs.python.orgreference. I am adopting the infixr levels from Haskell, which seem to be consistent with Python, at least for the operators that Sifflet uses.
| Operator information Arithmetic operators: + and - have lower precedence than *, , /, % | Comparison operators have precedence lower than any arithmetic operator. Here, I've specified associative = False, because association doesn't even make sense (well, it does in Python but not in other languages); (a == b) == c is in general not well typed.