134 lines
2.9 KiB
Python
134 lines
2.9 KiB
Python
import tokens
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from parser import Parser
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import enum
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class RunStatus:
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"""
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Base class for run status.
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These are returned whenever the runner does something.
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"""
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pass
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class MacroStatus(RunStatus):
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"""
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Returned when a macro is defined.
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Values:
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`was_rewritten`: If true, an old macro was replaced.
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`macro_label`: The name of the macro we just made.
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"""
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def __init__(
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self,
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*,
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was_rewritten: bool,
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macro_label: str
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):
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self.was_rewritten = was_rewritten
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self.macro_label = macro_label
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class StopReason(enum.Enum):
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BETA_NORMAL = ("#FFFFFF", "β-normal form")
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LOOP_DETECTED = ("#FFFF00", "loop detected")
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MAX_EXCEEDED = ("#FFFF00", "too many reductions")
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INTERRUPT = ("#FF0000", "user interrupt")
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class ReduceStatus(RunStatus):
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"""
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Returned when an expression is reduced.
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Values:
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`reduction_count`: How many reductions were made.
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`stop_reason`: Why we stopped. See `StopReason`.
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"""
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def __init__(
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self,
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*,
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reduction_count: int,
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stop_reason: StopReason,
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result: tokens.LambdaToken
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):
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self.reduction_count = reduction_count
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self.stop_reason = stop_reason
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self.result = result
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class Runner:
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def __init__(self):
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self.macro_table = {}
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# Maximum amount of reductions.
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# If None, no maximum is enforced.
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self.reduction_limit: int | None = 300
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def exec_command(self, command: str):
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if command == "help":
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print("This is a help message.")
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def reduce_expression(self, expr: tokens.LambdaToken) -> ReduceStatus:
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# Reduction Counter.
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# We also count macro expansions,
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# and subtract those from the final count.
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i = 0
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macro_expansions = 0
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while i < self.reduction_limit:
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r = expr.reduce(self.macro_table)
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expr = r.output
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# If we can't reduce this expression anymore,
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# it's in beta-normal form.
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if not r.was_reduced:
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return ReduceStatus(
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reduction_count = i - macro_expansions,
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stop_reason = StopReason.BETA_NORMAL,
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result = r.output
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)
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# Count reductions
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i += 1
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if r.reduction_type == tokens.ReductionType.MACRO_EXPAND:
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macro_expansions += 1
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return ReduceStatus(
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reduction_count = i - macro_expansions,
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stop_reason = StopReason.MAX_EXCEEDED,
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result = r.output
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)
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# Apply a list of definitions
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def run(self, line: str) -> RunStatus:
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e = Parser.parse_line(line)
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# If this line is a macro definition, save the macro.
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if isinstance(e, tokens.macro_expression):
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was_rewritten = e.label in self.macro_table
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e.exp.bind_variables()
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self.macro_table[e.label] = e.exp
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return MacroStatus(
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was_rewritten = was_rewritten,
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macro_label = e.label
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)
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# If this line is a command, do the command.
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elif isinstance(e, tokens.command):
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return self.exec_command(e.name)
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# If this line is a plain expression, reduce it.
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else:
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e.bind_variables()
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return self.reduce_expression(e)
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def run_lines(self, lines: list[str]):
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for l in lines:
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self.run(l)
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