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• the boolean constants true and false ;
• boolean variables (represented by symbols other than true, false, not, and, or, implies, and if) that can be bound to either true or false.
• the unary operator not .
• the binary operators and, or, and implies, and
• the ternary operator if.

foo

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The course staff is providing function parse and unparse in the file parser.ss that convert boolean expressions in Scheme notation to a simple inductively defined type called boolExp and vice-versa. The coding of parse and unparse is not difficult, but it is tedious (like most parsing) so the course staff is providing this code rather than asking students to write it.

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