Effectuate the binding of the heap cell to the address

Convenience wrapper to obtain the cell type

Convenience wrapper to obtain the cell value

Convenience wrapper for any cell types

Follows a possible reference chain until it reaches either an unbound REF
cell or a non-REF cell, the address of which it returns. The effect of
dereferencing is none other than composing variable substitutions.

Convenience wrapper for REF cell types

Convenience wrapper for STR cell types

Unification algorithm based on the UNION/FIND method [AHU74], where
variable substitutions are built, applied, and composed through
dereference pointers. The unification operation is performed on a
pair of store addresses, and applied for all functors and their
arguments, repeated iteratively until the stack is exhausted.