final Formula condition = intExpr.condition().accept(this);
final IntExpression thenExpr = intExpr.thenExpr().accept(this);
final IntExpression elseExpr = intExpr.elseExpr().accept(this);
ret = (condition==intExpr.condition() && thenExpr==intExpr.thenExpr() &&
elseExpr==intExpr.elseExpr()) ?
intExpr : condition.thenElse(thenExpr, elseExpr);
return cache(intExpr,ret);
}
/**
* Calls lookup(intExpr) and returns the cached value, if any.