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- Subject: Re: Soft Types System Proposal
- From: Asger Ottar Alstrup <aalstrup@...>
- Date: Mon, 01 Nov 2004 19:08:07 +0100
Roberto Ierusalimschy wrote:
Basically, my reasoning is that the simple type check solution would
cover 90% of the demands at a very low cost. In other words, the
gain/cost ratio is excellent for the simple type checker.
The best way to support that claim is with a working prototype. Why
don't you try to implement your idea?
That is true, and a fair request to back up my claims. If I can find the
time, my plan would be this:
1) Extend the parser to support type annotations a few places in the
grammar: In particular, variable and function declarations.
2) Add a simple typing pass when the syntax tree is built, which has two
a) Bubble types up from leaves in the syntax tree in a post-order
depth first traversal - i.e. type deduction.
b) A second traversal, which checks that the deduced types matches
any declared types.
Can you give me a few pointers to where to start? I have never looked at
the source code for the compiler. Where can I extend the parser, where
can I extend the syntax tree with a type field, and where can I hook up
such a new typing pass? Is there an example of a tree traversal somewhere?
Asger Ottar Alstrup