Re: Errors and Type checking. (Anton Ertl)
Tue, 12 Jan 1993 09:24:45 GMT

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Newsgroups: comp.compilers
From: (Anton Ertl)
Organization: Institut fuer Computersprachen, Technische Universitaet Wien
Date: Tue, 12 Jan 1993 09:24:45 GMT
References: 93-01-041 93-01-065
Keywords: performance, debug (J. Giles) writes:
> Most errors are not syntactic or static semantic errors (like type
> errors). The vast majority of debugging time is spent isolating and
> correcting problems which are not - and cannot be - found by the
> typechecks no matter how strict your type system is.

I can confirm this from experience with languages that do not check types
at all (e.g. Forth). I have not found type errors to be a problem. There
are two reasons for this:

1) I make fewer type errors than when programming in a compile-time
type-checked language. I.e., I am more careful. It probably takes a bit of
time to develop that programming mode.

2) When I make a type error, it is usually easy to catch and correct (It
helps if the language is interactive).

I think the more problematic type errors are those that the type checker
does not check, e.g. a search tree that is not sorted. Of course, this
sort of error could be caught with compile-time assertion checkers, but
somehow this technology has not caught on.

- anton
M. Anton Ertl

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