Restriction: The two <term>s in an equation must have the same sort. This
sort must be Bool if the equality operator is <=>.
Examples
x + 0 = x
x <= y <=> x < y \/ x = y
x | y <=> \E z (y = x*z)
Usage
LP treats equations in the same manner as it treats formulas. Indeed, any
formula is logically equivalent to an equation: F is logically equivalent
to F <=> true.