NewApplyRuleTask return a new apply rule task.

NewOptGroupExpressionTask return a targeting optimizing group expression task.

NewOptGroupTask returns a new optimizing group task.

NewSimpleTaskScheduler return a simple task scheduler, init logic included.

ApplyRuleTask is a wrapper of running basic logic union of scheduling apply rule.

BaseTask is base task wrapper structure for encapsulating basic things.

OptGroupExpressionTask is a wrapper of running logic of exploring group expression.

OptGroupTask is a wrapper of running logic of exploring a group.

SimpleTaskScheduler is defined for serializing scheduling of memo tasks.

Stack is used to store the optimizing tasks created before or during the optimizing process.