| 1 | # Show off "first class variants" / case classes.
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| 2 | #
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| 3 | # Takeaways:
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| 4 | # - metalanguage affects the language
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| 5 | # - metalanguage design / code compression
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| 6 |
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| 7 | # Based on frontend/syntax.asdl
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| 8 |
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| 9 | module demo {
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| 10 |
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| 11 | # Product type
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| 12 | Token = (int id, int length, int col, str line)
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| 13 |
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| 14 | word_part =
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| 15 | Literal %Token
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| 16 | | TildeSub(str? user_name)
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| 17 |
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| 18 | value =
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| 19 | Int(int i)
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| 20 | | Str(str s)
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| 21 |
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| 22 | expr =
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| 23 | Var %Token # a variable name to evaluate
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| 24 | | Const(Token c, value val)
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| 25 |
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| 26 | # Source location for errors
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| 27 | loc =
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| 28 | Missing
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| 29 | | Token %Token
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| 30 | # Another example from Oils
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| 31 | #| ArgWord %CompoundWord
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| 32 | }
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