search:common

common_expr(:ChildParentGoal, +Expr1, -Factor1, +Expr2, -Factor2, -CommonExpr) is nondet

Finds a common base expression CommonExpr for two input expressions Expr1 and Expr2 (typically units or quantities), along with their respective scaling factors Factor1 and Factor2.

The relationship established is that `Expr1*Factor1 = Expr2*Factor2 = CommonExpr`.

This predicate is tabled to memoize its results. It employs an iterative deepening approach to search for the closest common ancestor of Expr1 and Expr2. The search expands definitions (guided by the ChildParentGoal predicate, e.g., for unit parents or quantity parents) to establish this commonality.

Arguments:

`ChildParentGoal`	- A meta-argument (predicate name) that defines how to expand or find parents of elements within the expressions (e.g., `unit_parent` for units, `alias_or_child_quantity_parent` for quantities).
`Expr1`	- The first input expression (e.g., `si:metre`, `isq:speed`).
`Factor1`	- The numerical scaling factor associated with `Expr1` in the context of the common relationship.
`Expr2`	- The second input expression.
`Factor2`	- The numerical scaling factor associated with `Expr2` in the context of the common relationship.
`CommonExpr`	- The common base expression derived from `Expr1` and `Expr2`.