36 lines
550 B
Plaintext
36 lines
550 B
Plaintext
module fostr
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imports
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Common
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context-free start-symbols
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Ex
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context-free sorts
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Ex
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context-free syntax
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Ex.Int = INT
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Ex.Stdio = <stdio>
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Ex.Sum = {Ex "+"}+
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Ex.Receives = [[Ex] << [Ex]] {left}
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Ex.Enters = [[Ex] >> [Ex]] {left}
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Ex = <(<Ex>)> {bracket}
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context-free priorities
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Ex.Enters
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> Ex.Sum
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> Ex.Receives,
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// prevent cycle: no singletons
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Ex.Sum <0> .> {Ex "+"}+ = Ex,
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// flat: no Sum immediately in Sum:
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{Ex "+"}+ = Ex <0> .> Ex.Sum,
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{Ex "+"}+ = {Ex "+"}+ "+" Ex <2> .> Ex.Sum
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