5 ms·

The if(0==flag) is perfectly valid for avoiding if(flag=0) bugs. Of course, I'd use if(!flag)

• tjsnyder 16y ago
  Honestly, this is like arguing tabs vs spaces.
  • lukeschlather 16y ago
    Tabs vs. spaces is basically an implementation detail of the editor. The point is that the code should always look the same. This is a semantic issue that doesn't even go away in pseudocode.
• kenjackson 16y ago
  Any modern should not allow 'if(flag=0)'. Any non-modern language should flag a warning on that. And this warning should be set to be an error by any reasonable developer.
  • rcfox 16y ago
    What about while? while(flag = 0) looks like a similar error, but while(foo = read()) is a common idiom.
    • brownleej 16y ago
      I think some compilers give a warning on while(foo = read()) but not on while((foo = read())).
      • CamperBob 16y ago
        That would be a broken compiler.
        • tbrownaw 16y ago
          No, I'm pretty sure that's intentional specifically to permit that idiom.
          • __david__ 16y ago
            It's usually a warning that you have to turn on explicitly, or one that you can at least turn off (thank heavens).
    • CamperBob 16y ago
      It's not the choice of keyword that (should) trigger the warning. It's the simple fact that an expression that evaluates to boolean contains an '='. This potential error is trivial for any compiler to flag.
  • Jach 16y ago
    Personally I'm more against "=" being the assignment operator, which should be ":=". But I have no problems with the actual syntax so long as it's clearly defined what (x = y) returns. (Does it return y? x? true if assignment was successful? Does it call a operator=() function that blows up the moon?) In languages where the line between statement and expression is nil it would be especially odd to flag this as illegal. Flash Builder's Actionscript compiler has saved me from that a couple times in memory, though, so I agree it should be a warning if you don't wrap it in extra parens. gcc also will complain.
    • chromatic 16y ago
      Personally I'm more against "=" being the assignment operator, which should be ":=". The problem with := is that you run the risk of the Pascal trap, in that no language which uses := for assignment has ever become more popular than Pascal.
      • redthrowaway 16y ago
        In general, I just don't like hitting shift, and so am opposed to :=.
        • Jach 16y ago
          Let's compromise and make it ;=.
          • deleted 16y ago
            [deleted]
          • redthrowaway 16y ago
            I'd rather if the compiler simply determined whether or not it was used as an assignment or comparison and just go with a single =.
  • bradly 16y ago
    > Any modern should not allow 'if(flag=0)'. This is how you set default values for optional argument in Ruby and is very common.
    • chc 16y ago
      I have never seen "if foo = 0" used to set a value for an optional argument in Ruby. It would either be "def bar(foo=0)" or "foo ||= 0". Can you give any example of what you're talking about?
      • bradly 16y ago
        My mistake. I didn't read parent carefully enough. Although it is common to see something like: if(@post = Post.find(params[:id])) render @post else render 'Post not found' end
  • xhuang 16y ago
    I think PHP allow assignment in 'if'
• zokier 16y ago
  In C++ flag==0 and !flag are not always the same, but depending on the type of flag, and if that type(or any its parents) has either or both of == or ! operators overloaded.
• InclinedPlane 16y ago
  Pray tell which compiler you are using that won't throw a warning on variable assignment in a condition?