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CSE 401: PL/0 - Original Syntax Description |
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The following grammar describes the base version of the PL/0 language, i.e., PL/0 as implemented by the base compiler distributed to you at the begining of the quarter.
It uses some syntactic sugar that is not strictly BNF, e.g. braces {} mean "0 or more", and brackets [ ] mean "optional".
You might also want to visit the extended BNF (but this link won't work until after HW#2 is turned in).
| Program | ::= | module Id ; Block Id . | |
| Block | ::= | DeclList begin StmtList end | |
| DeclList | ::= | { Decl ; } | |
| Decl | ::= | ConstDecl | VarDecl | ProcDecl | |
| ConstDecl | ::= | const ConstDeclItem { , ConstDeclItem } | |
| ConstDeclItem | ::= | Id : Type = ConstExpr | |
| ConstExpr | ::= | Id | Integer | |
| VarDecl | ::= | var VarDeclItem { , VarDeclItem } | |
| VarDeclItem | ::= | Id : Type | |
| ProcDecl | ::= | procedure Id ( [ FormalDecl {, FormalDecl }] ) ; Block Id | |
| FormalDecl | ::= | Id : Type | |
| Type | ::= | int | |
| StmtList | ::= | { Stmt ; } | |
| Stmt | ::= | CallStmt | AssignStmt | OutStmt | IfStmt | WhileStmt | |
| CallStmt | ::= | Id ( [ Exprs ] ) | |
| AssignStmt | ::= | LValue := Expr | |
| LValue | ::= | Id | |
| OutStmt | ::= | output := Expr | |
| IfStmt | ::= | if Test then StmtList end | |
| WhileStmt | ::= | while Test do StmtList end | |
| Test | ::= | odd Sum | Sum Relop Sum | |
| Relop | ::= | < | <= | = | >= | > | <> | |
| Exprs | ::= | Expr { , Expr } | |
| Expr | ::= | Sum | |
| Sum | ::= | Term { (+ | -) Term } | |
| Term | ::= | Factor { (* | /) Factor } | |
| Factor | ::= | - Factor | LValue | Integer | input | ( Expr ) |
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