On Wed, 27 Jun 2001, Hamilton Richards wrote:
At 7:57 PM -0500 6/25/01, you wrote:
BTW I teach a "programming languages" course which includes an introduction to Haskell and an introduction to parsing and compiling. The students modify an interpreter that I wrote. The complete Haskell source for the language (simple block structured imperative language with a single integer daya type) is only 600 lines, of which about half is the parser. This compares favourably with a similar toy compiler in C++ that was used before I took over the course --- it ran to well over 5000 lines!
That's very interesting to me, since I, too, teach a programming languages course which includes an intro to Haskell and to parsing. An interpreter for an imperative language would pull a lot of topics nicely together.
That was my motivation in developing the interpreter. I think it has worked pretty well. Although a toy it is "real" enough to provide a genuine intro to language implementation issues like parsing, symbol table maintenance, semantic checks, run time stack etc.
Do your students know any Haskell coming into the course, or is your introduction to Haskell their first taste of it?
This is their first taste of Haskell. Some love it and some never become comfortable with it.
Does the imperative language include procedures? With what methods of binding arguments to parameters? What sort of modifications can the students manage?
The language is modelled on Pascal: it uses the same scoping rules as Pascal and supports nested procedure declarations. Apart from minor syntactic differences (like { } not begin ... end) the main differences are - single integer data type - no functions - parameter passing is call by value - all operators (usual relational & arithmentic) have same precedence - if and while are only control structures - io is limited to reading and writing a single integer at a time So far over the past few years I've set questions such as adding - unary operators - parenthesised expressions - a C-like ternary ? : expression - Haskell-like comments - for statements - repeat .. until post test loops - constant declarations - functions - call by reference parameters - call by value-result parameters The last 4 have been the most challenging but good average students have generally succeeded in completing such questions. Richard -- Dr Richard Watson rwatson@usq.edu.au Dept of Mathematics & Computing phone: +61 7 4631 5546 University of Southern Queensland FAX: +61 7 4631 5555 Toowoomba Qld 4350, AUSTRALIA http://www.sci.usq.edu.au