47 lines
1.1 KiB
Python
47 lines
1.1 KiB
Python
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def is_variable(b):
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return isinstance(b, str) and b.isupper()
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def unify(ctx, a, b):
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"""
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a is the concrete type
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b is the type with parameter
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lower case means primitive type
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upper case means type variable
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list and tuples are just list and tuples
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"""
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if isinstance(ctx, str):
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return ctx
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if is_variable(b):
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if b in ctx:
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b = ctx[b]
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else:
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ctx[b] = a
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return ctx
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if isinstance(a, list) and isinstance(b, list):
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return unify(ctx, a[0], b[0])
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elif isinstance(a, tuple) and isinstance(b, tuple) and len(a) == len(b):
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old = ctx
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for x, y in zip(a, b):
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old = unify(old, x, y)
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return old
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else:
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if a == b:
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return ctx
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else:
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return f"{a} != {b}"
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def check_eq(a, b):
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unifier = unify({}, a, b)
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print(f"{a} <- {b}\n{unifier}\n")
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check_eq('a', 'A')
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check_eq(['a'], 'A')
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check_eq(['a'], ['A'])
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check_eq(['a'], ['b'])
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check_eq([('a', 'a', 'b')], ['A'])
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check_eq([('a', 'a', 'b')], [('A', 'A', 'B')])
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check_eq([('a', 'a', 'b')], [('A', 'A', 'A')])
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