Lab 5

• Develop a (more robust version of the) parser that we sketched on Wednesday in class. It should accept only well-formed s-expressions, and output AE’s. It should check the length of the list. It should include the `with’ form. It should signal an error, by calling error, when the input is not well-formed. Here’s a grammar for the language:

  WAE		=		num
  		|		{+ WAE WAE}
  		|		{- WAE WAE}
  		|		{with {id = WAE} WAE}
  		|		id

  ... where id is an arbitrary symbol.

  Write lots of test cases. Use the test/exn form to test your error code.

  This will be the basis for the parser that is a part of your remaining assignments, so it would behoove you to do a good job.

• From HtDP: Exercises 12.4.1 and 12.4.2. Two hints: write test cases first, and follow the template for functions on lists.

If time: exercises 32.2.1,2,3. (modeling missionaries and cannibals)