reversing the comparison
in [Visual Basic]
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From: Tom Shelton on 20 Jul 2010 11:02 Paul Clement was thinking very hard : > On Mon, 19 Jul 2010 21:28:37 -0400, "Kevin Provance" <k(a)p.c> wrote: > > � Hey C++ guys, what is the advantage or purpose of this? > � > � If (FALSE == SomeFunction()) > � { > � ... > � } > � > � Why put FALSE == instead of the function first, like we usually do? > > Looks like the Yoda School of Programming to me. Coded properly, the > comparison to FALSE isn't even necessary. > It's C++ code.... Older C++ didn't define a bool type or have any concept of a boolean value. That mades these types of comparisons necessary, and the reverse test was to prevent the old bug of accidently doing an assignment in the test. -- Tom Shelton
From: DanS on 20 Jul 2010 11:42 >> � Why put FALSE == instead of the function first, like we >> usually do? >> >> Looks like the Yoda School of Programming to me. Coded >> properly, the comparison to FALSE isn't even necessary. >> > > It's C++ code.... Older C++ didn't define a bool type or > have any concept of a boolean value. That mades these > types of comparisons necessary, and the reverse test was to > prevent the old bug of accidently doing an assignment in > the test. Since when is a programmer's own deficiency a bug ? I've made that error in C, and never blamed anyone but myself.
From: Tom Shelton on 20 Jul 2010 12:09 DanS formulated on Tuesday : >>> � Why put FALSE == instead of the function first, like we >>> usually do? >>> >>> Looks like the Yoda School of Programming to me. Coded >>> properly, the comparison to FALSE isn't even necessary. >>> >> >> It's C++ code.... Older C++ didn't define a bool type or >> have any concept of a boolean value. That mades these >> types of comparisons necessary, and the reverse test was to >> prevent the old bug of accidently doing an assignment in >> the test. > > Since when is a programmer's own deficiency a bug ? > A bug is any incorrect behavior in the program - which in this old case maybe the result of a typo or as you say, programmer deficiency. What does this actualy have to do with my response? > I've made that error in C, and never blamed anyone but myself. As have I. The idea of the reverse test, and why it is actually a common C/C++ idiom is because it helps prevent bugs. It's called defensive coding... It turns a simple typo into a compilation error. More modern languages usually design there conditional statements to only work on boolean type values - so an accidental assignment is always caught by the compiler. -- Tom Shelton
From: Karl E. Peterson on 20 Jul 2010 12:09 Kevin Provance explained on 7/19/2010 : > "Karl E. Peterson" <karl(a)exmvps.org> wrote in message > news:i22va8$qjs$1(a)news.eternal-september.org... >> >> Are you testing for true or false? If you put the False up front, it's >> really clear when you make an exception to the normal situation. > > I'm converting some C++ code to VB (specifically dealing with CAB files) and > I noticed the call was...reversed. I was just curious if there was a > specific reason why. Tis all. :-) Heh, actually, that question was directed at the code snippet that you snipped. <g> Rewinding... "Karl E. Peterson" <karl(a)exmvps.org> wrote in message > But what if the function has eight or nine parameters, and you end up with: > > If SomeFunction(Byval aLongVarName, ByVal SomeMoreData, ByVal Blah, > By<clipped> > > Are you testing for true or false? If you put the False up front, it's > really clear when you make an exception to the normal situation. The <clipped> there was supposed to represent the right-edge of the code window. IOW, you are unable to read the entire line of code, because it's wider than your window. In *most* cases, you'd simply be testing for a non-zero (true) return, so there'd be no need to read it all. But what if you want to test for a 0 (false) return? If you put the =0 or =False at the end of the line, it could easily be out of view and not intuitively noticeable. That would be a justification for putting this less common test up front, IMO. YMMV, of course. :-) -- ..NET: It's About Trust! http://vfred.mvps.org
From: Paul Clement on 20 Jul 2010 13:26
On Tue, 20 Jul 2010 09:02:19 -0600, Tom Shelton <tom_shelton(a)comcast.invalid> wrote: � Paul Clement was thinking very hard : � > On Mon, 19 Jul 2010 21:28:37 -0400, "Kevin Provance" <k(a)p.c> wrote: � > � > � Hey C++ guys, what is the advantage or purpose of this? � > � � > � If (FALSE == SomeFunction()) � > � { � > � ... � > � } � > � � > � Why put FALSE == instead of the function first, like we usually do? � > � > Looks like the Yoda School of Programming to me. Coded properly, the � > comparison to FALSE isn't even necessary. � > � � It's C++ code.... Older C++ didn't define a bool type or have any � concept of a boolean value. That mades these types of comparisons � necessary, and the reverse test was to prevent the old bug of � accidently doing an assignment in the test. So let me get this straight... "If (FALSE)" in C++ evaluates to True or is it an invalid statement? I haven't work with an older C-language in over 25 years so I can't recall how this functions. It's still backwards with respect to readability. ;-) Paul ~~~~ Microsoft MVP (Visual Basic) |