WIP: dataclasses <-> grammar + input

marzipan/src/letfuncdecl.py

@@ -0,0 +1,72 @@
+import sys
+from dataclasses import dataclass
+from typing import List, Optional
+
+from lark import Lark, Transformer, ast_utils, v_args
+from lark.tree import Meta
+
+this_module = sys.modules[__name__]
+
+
+@dataclass
+class Ident(ast_utils.Ast):
+    ident: str
+
+
+@dataclass
+class Pterm(ast_utils.Ast, ast_utils.AsList):
+    pterm: Ident | int | List
+
+
+@dataclass
+class LetfunDecl(ast_utils.Ast):
+    ident: Ident
+    typedecl: Optional[List[Ident]]
+    pterm: Pterm
+
+
+parser = Lark("""
+start: letfun_decl
+_non_empty_seq{x}: x ("," x)*
+_maybe_empty_seq{x}: [ _non_empty_seq{x} ]
+IDENT:/[a-zA-Z][a-zA-Z0-9À-ÿ'_]*/
+NAT: DIGIT+
+typeid: IDENT
+typedecl: IDENT ":" typeid
+pterm: IDENT | NAT | "(" _maybe_empty_seq{pterm} ")"
+letfun_decl: "letfun" IDENT [ "(" [ typedecl ] ")" ] "=" pterm "."
+%import common (DIGIT, WS)
+%ignore WS
+""")
+
+
+class ToAst(Transformer):
+    def NAT(self, n):
+        n = int(n)
+        assert n > 0, "NAT must be an integer > 0"
+        return n
+
+    @v_args(inline=True)
+    def start(self, x):
+        return x
+
+
+transformer = ast_utils.create_transformer(this_module, ToAst())
+
+
+def parse(input: str):
+    tree = parser.parse(input)
+    print(tree)
+    ast = transformer.transform(tree)
+    print(ast)
+    # ast -> input
+
+
+if __name__ == "__main__":
+    parse("""
+    letfun test = foo .
+    """)
+
+    # parse("""
+    # letfun test ( foo : bar ) = foo .
+    # """)