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Seven errors game

Pascal Cuoq - 11th Jan 2011

If you have seen the basic presentation of the value analysis, you may remember the following function.


void abs(int y) 
{ 
  if (y >= 0) 
    {  
      r = y; 
      return; 
    } 
  else 
    { 
      r = -y; 
      return; 
    } 
}


\Why the two ugly return; statements in a function that needs none?" I almost hear you ask. Here is why: without these spurious return; statements you may need to explain where the {2; 3; } set comes from in the screenshot below.


Before


In the screenshot the user has clicked on variable r in the then branch of the if. The bottom panel displays information about the value of r before the assignment and also the possible values of r at the beginning of the successor of the assignment. The intention is to let the user see the effect the statement has on x but in this case this only produces confusion.

Behold the new graphical user interface that Boris and I have spent the afternoon on (pay attention: the difference is subtle):


After

Pascal Cuoq
11th Jan 2011