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#lang ragg
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;; recursive rules destucture easily in the expander
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program : [line [CR line]*]
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line: INTEGER statement+
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statement : "END"
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| "FOR" ID "=" expr "TO" expr ["STEP" expr]
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| "GOTO" expr
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| "IF" expr "THEN" (statement | expr) ; change: add expr
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| "INPUT" print-list ";" ID
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| ["LET"] ID "=" expr ; change: make "LET" opt
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| "NEXT" ID+
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| "PRINT" print-list
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| REM-COMMENT
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print-list : [expr [";" [print-list]]]
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expr : sum [("=" | ">" | ">=" | "<" | "<=" | "<>") expr]
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sum : product [("+" | "-") sum]
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product : value [("*" | "/") product]
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value : ID ["(" expr* ")"]
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| INTEGER
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| STRING
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| REAL
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