ITEC 380 2016summerIII ibarland

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Q0
Interpreting Q

The language Q0

  Expr       ::= Num | ParenExpr | BinExpr | ParityExpr
  ParenExpr  ::= [[ Expr ]]
  BinExpr    ::= ( Expr BinOp Expr )
  ParityExpr ::= parity Expr even: Expr odd: Expr ;
  BinOp      ::= add | sub | mul 

Discussion

• Give five example programs (Exprs) written in Q0.
• Give their parse trees.
• How should we represent these trees, internally? (In Racket, and equivalently in Java).

Where we're headed

• For interpreting this language, we will implement three methods:
  • parse, which turns source-code into an internal representation,
  • toString which turns internal representation back into source-code,
  and
  • eval, which actually interprets the program, returning a value (a number for Q0-Q2, and a number-or-function in Q3).
  I recommend implementing and testing the methods in this order. Some test-cases will be provided. There might be other helper functions to implement as well.

Q0 Implementations

• Java: Q0-java/ (browse the directory), or see the .jar.
• Q0.rkt, with helper files scanner.rkt (and, scanner-demo.rkt); test cases expr-test-Q0.rkt.

  Note:Download the racket files, and then choose Open… from DrRacket. Do not copy/paste into an empty DrRacket window, since that window is probably using a student-language, and some of the files below use full racket.

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©2015, Ian Barland, Radford University Last modified 2016.Jul.10 (Sun)

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