Abstract

Machine [21], is to pass the ith argument in register i: if the ith argument happens to be a variable (which typically corresponds to an output argument), the value passed is a pointer to the location of the variable (which may be either on the stack or on the heap). In effect, this policy passes output arguments by reference. The policy is motivated by the fact that, in general, Prolog procedures do not have any notion of input and output arguments, and a particular argument to a procedure can be an input argument in one invocation and an output argument in another. Returning outputs in memory allows a simple and uniform treatment of communication between procedure activations under these circumstances. The main advantage of a memory return policy, apart from simplicity, is that it never prevents tail call optimizations, since one memory location is as good as any other. Because of this, there is no need to insert code to move a value to a preferred location, as in Example 3.2. Thus, ...

Citations