What is wrong with this forall -statement in CPLEX?

问题

I am trying to answer here but err:

   forall(t in 0..4){
    a[t]<=z[t];
    -a[t]<=z[t];
    x[t+1]==x[t]+v[t];
    v[t+1]==v[t]+a[t];
   }           

回答1:

The recursive equation enters into un-initialized interval hence index out of exeption. You can avoid this bug by tweaking: initialize not-needed valuations and assign them to zero.

This creates some overhead but simplifies the logic, cannot think about any simpler way to do this.

来源：https://stackoverflow.com/questions/13291906/what-is-wrong-with-this-forall-statement-in-cplex