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constants: dict[str, str] = {
# Registers
"ra": "0",
"rb": "1",
"rc": "2",
"rd": "3",
"re": "4",
"rf": "5",
"rg": "6",
"rh": "7",
# ALU instructions
"al_plus": "0",
"al_minus": "1",
"al_and": "2",
"al_or": "3",
"al_xor": "4",
"al_slr": "5",
"al_sar": "6",
"al_sll": "7",
# ALU flags
"carry": "0",
"overflow": "1",
"zero": "2",
"sign": "3",
}
Labels = dict[str, int]
def check_size(bits: int, val: int) -> None:
if val >= 2 ** bits:
raise Exception(f"Value does not fit in {bits} bits: {val}")
def eval_symbol(labels: Labels, c: str) -> str:
if c in labels:
return str(labels[c])
if c in constants:
return constants[c]
return c
def eval_expr(labels: Labels, expr: str, bits: int = 16) -> int:
expr = expr.lower()
expr = eval_symbol(labels, expr)
ret = eval(expr, labels.copy()) # eval as Python expr
check_size(bits, ret)
return ret
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