Top Mode Coercion Runtime Library
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When a relational operator formula involving symbolic variables is computed, it may cause a constraint to be placed on the environment. The kinds of constraints that can be placed there are summarized in this section.

If the relational operator formula is not in the format of a constraint to begin with, it is transformed according to the rules of algebra so that it is. This may require coercing the mode of some symbolic variables to input by backtracking out those variables. If the backtracking-out fails, a run-time error, "Too many backtracks..." is raised, as usual.

The setting of a constraint will cause the relational operator formula to fail if the constraint is not compatible with constraints already in the environment; for instance, x < 3 where x > 4 is already in the environment.

The following list summarizes the formats of all possible constraints that can be in the environment, rel here always refers to one of the relational operators (< , > , <=, >=, =,or <>).

Top Mode Coercion Runtime Library