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From: dmg@ssc-vax.uucp (David M Geary)
Newsgroups: comp.object,comp.lang.misc
Subject: Re:  Run-time Type Errors in Smalltalk
Message-ID: <3865@ssc-bee.ssc-vax.UUCP>
Date: 17 Apr 91 19:54:18 GMT
Sender: news@ssc-vax.UUCP
Organization: Boeing Aerospace & Electronics
Lines: 31
Originator: dmg@ssc-vax

]  David Gudeman
]] Douglas Surber

]If they hadn't caught those errors by static typing they would have caught
]them by testing -- the same way the found the other 90% of the errors.
]This logic error combined with the strident tone of the article
]suggests that your convictions are affecting your thinking.

]]The real question is how long would it take them to catch those errors
]]by testing?  The type checker catches them all first time every time.
]]Admittedly not every error, but reducing the number of errors by 10%
]]before you even begin testing sounds like a win to me.  

  Sounds like a win to me, also.  However, there are two caveats:
  
1)  Since dynamic typing allows more expressiveness and a greater degree
    of reusability than a statically typed language, code in a statically 
    typed language may be 10% (or more) larger than the "same" code in a 
    dynamically typed language.  So, while some errors have been ironed out
    before testing, testing may have more to test.

2)  Errors caused by circumvention of the type system in a statically typed
    language may *not* be caught by the compiler, and are difficult to
    track down.  In fact, I demonstrated such an error in an earlier posting.

]]Further, the type checker finds type errors even in code that, for one
]]reason or another, is never excersized during testing.  Again not every
]]error, but a 10% reduction is still something.

  Again, realize that the type checker will not find errors that fall into
category #2 above.