From 323c7a62828b18ccd2652bcfdc6de4824bdedde5 Mon Sep 17 00:00:00 2001
From: Michael Zhang <mail@mzhang.io>
Date: Tue, 8 Jun 2021 19:56:30 -0500
Subject: [PATCH] initial

---
 .gitignore   |  2 ++
 Justfile     |  2 ++
 arith.ag     | 13 +++++++++++++
 gen.py       | 22 ++++++++++++++++++++++
 grammar.lark | 44 ++++++++++++++++++++++++++++++++++++++++++++
 main.py      | 35 +++++++++++++++++++++++++++++++++++
 mypy.ini     |  2 ++
 7 files changed, 120 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Justfile
 create mode 100644 arith.ag
 create mode 100644 gen.py
 create mode 100644 grammar.lark
 create mode 100644 main.py
 create mode 100644 mypy.ini

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..791e803
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+.mypy_cache
+gen/
diff --git a/Justfile b/Justfile
new file mode 100644
index 0000000..029ae70
--- /dev/null
+++ b/Justfile
@@ -0,0 +1,2 @@
+watch:
+	watchexec -ce py -i gen 'mypy *.py && python gen.py && mypy gen/*.py'
diff --git a/arith.ag b/arith.ag
new file mode 100644
index 0000000..6d4adf7
--- /dev/null
+++ b/arith.ag
@@ -0,0 +1,13 @@
+iface Node {
+	val: int,
+}
+
+node Expr : Node {
+	<l:Expr> "+" <r:Expr> => {
+		self.val = l.val + r.val;
+	}
+	<l:Expr> "*" <r:Expr> => {
+		self.val = l.val * r.val;
+	}
+	<n:r"[0-9]+"> => { self.val = parseInt(n); }
+}
diff --git a/gen.py b/gen.py
new file mode 100644
index 0000000..ac6c0d8
--- /dev/null
+++ b/gen.py
@@ -0,0 +1,22 @@
+import textwrap
+import os
+from lark import Lark
+
+p = Lark(open("grammar.lark").read())
+
+if __name__ == "__main__":
+	with open("arith.ag") as f:
+		data = f.read()
+
+	t = p.parse(data)
+	print(t)
+
+	if not os.path.exists("gen"):
+		os.makedirs("gen")
+	with open("gen/arith.py", "w") as f:
+		f.write(textwrap.dedent("""
+			from typing import Generic, TypeVar
+			T = TypeVar('T')
+			class Thunk(Generic[T]):
+				pass
+		"""))
diff --git a/grammar.lark b/grammar.lark
new file mode 100644
index 0000000..9e2a3bf
--- /dev/null
+++ b/grammar.lark
@@ -0,0 +1,44 @@
+start: decl*
+
+decl: iface
+	| node
+
+iface: IFACE IDENT "{" iface_field (COMMA iface_field)? COMMA? "}"
+iface_field: IDENT COLON IDENT
+
+node: NODE IDENT COLON IDENT "{" node_prod* "}"
+node_prod: prod THICCARROW "{" (equation SEMI)* "}"
+prod: sym*
+sym: IDENT
+	| LANG IDENT COLON node_ref RANG
+	| STRING
+node_ref: IDENT
+	| STRING
+equation: expr EQ expr
+
+expr: expr DOT expr
+	| expr ADD expr
+	| expr MUL expr
+	| expr LPAR args RPAR
+	| IDENT
+args: expr (COMMA expr)? COMMA?
+
+IDENT: /([a-zA-Z][a-zA-Z0-9_]*)|(_[a-zA-Z0-9_]+)/
+IFACE: "iface"
+NODE: "node"
+LANG: "<"
+RANG: ">"
+ADD: "+"
+MUL: "*"
+COMMA: ","
+COLON: ":"
+LPAR: "("
+RPAR: ")"
+EQ: "="
+DOT: "."
+SEMI: ";"
+THICCARROW: "=>"
+
+%import python.STRING
+%import common.WS
+%ignore WS
\ No newline at end of file
diff --git a/main.py b/main.py
new file mode 100644
index 0000000..82e7ce0
--- /dev/null
+++ b/main.py
@@ -0,0 +1,35 @@
+from typing import Generic, TypeVar, Optional, Callable
+
+T = TypeVar("T")
+
+class Thunk(Generic[T]):
+	value: Optional[T]
+
+	def __init__(self, func: Callable[[], T]):
+		self.func = func
+		self.value = None
+
+	def get(self) -> T:
+		if self.value is None:
+			self.value = self.func()
+		return self.value
+
+class Node:
+	value: Thunk[int]
+
+class Add(Node):
+	def __init__(self, left: Node, right: Node):
+		self.value = Thunk(lambda: left.value.get() + right.value.get())
+
+class Mul(Node):
+	def __init__(self, left: Node, right: Node):
+		self.value = Thunk(lambda: left.value.get() * right.value.get())
+
+class Lit(Node):
+	def __init__(self, num: int):
+		self.num = num
+		self.value = Thunk(lambda: num)
+
+if __name__ == "__main__":
+	tree = Add(Mul(Lit(3), Lit(4)), Lit(5))
+	print(tree.value.get())
diff --git a/mypy.ini b/mypy.ini
new file mode 100644
index 0000000..70a2ffb
--- /dev/null
+++ b/mypy.ini
@@ -0,0 +1,2 @@
+[mypy]
+strict = True
\ No newline at end of file