excel_backend.py

factorial = (
	("op", "a", "input"),
	("loop",
		("phi", "a", "a", "a2"),
		("phi", "b", 1, "b2"),
		("op", "b2", "mul", "a", "b"),
		("op", "a2", "sub", "a", 1),
		("op", "loop-condition", "gt", "a", 0),
		"loop-condition"
	)
)

def translate(program):
	rlabel = []
	row = []

	def atlevel(expr, level):
		if isinstance(expr, str) and expr[:2] == "RC" and level != 0:
			return "R[{}]{}".format(level, expr[1:])
		return expr

	def t_phi(scopes, phiindices, selector, x):
		if x[0] != "phi":
			return

		expr = "RC[-1]"
		for i, ((level, scope), var) in enumerate(zip(scopes, x[2:])):
			subexpr = atlevel(scope.get(var, var), level)
			expr = "IF({} = {}, {}, {})".format(selector, i, subexpr, expr)

		row[phiindices.pop(0)] = "="+expr

	def t_non_phi(scope, phiindices, x):
		if x[0] == "loop":
			body = x[1:-1]
			exit = x[-1]
			inner_scope = scope.copy()
			inner_phiindices = []
			for x2 in body:
				t_non_phi(inner_scope, inner_phiindices, x2)
			exit = atlevel(inner_scope.get(exit, exit), -1)
			for x2 in body:
				t_phi([(0, scope), (-1, inner_scope)], inner_phiindices, exit, x2)
			
		elif x[0] == "op":
			name = x[1]
			opcode = x[2]
			args = [scope.get(arg, arg) for arg in x[3:]]
			tr = {"mul": "={}*{}", "gt": "={}>{}", "sub": "={}-{}", "input": ""}
			expr = tr[opcode].format(*args)
			print(name, opcode, args, tr, expr)
			rlabel.append(name)
			row.append(expr)
			scope[name] = "RC{}".format(len(row))

		elif x[0] == "phi":
			phiindices.append(len(row))
			rlabel.append("phi "+x[1])
			row.append(None) # placeholder
			scope[x[1]] = "RC{}".format(len(row))

		else:
			assert False

	def t_main(x):
		scope = {}
		for x2 in x:
			t_non_phi(scope, None, x2)

	t_main(program)
	print(";".join(rlabel))
	print(";".join("0" for _ in row))
	print(";".join(row))

translate(factorial)