Enum MergeFn 

pub enum MergeFn {
    AssertEq,
    UnionId,
    Primitive(ExternalFunctionId, Vec<MergeFn>),
    Function(FunctionId, Vec<MergeFn>),
    Old,
    New,
    Const(Value),
}

How to resolve FD conflicts for a table.

Variants

AssertEq

Panic if the old and new values don’t match.

UnionId

Use congruence to resolve FD conflicts.

Primitive(ExternalFunctionId, Vec<MergeFn>)

The output of a merge is determined by applying the given ExternalFunction to the result of the argument merge functions.

Function(FunctionId, Vec<MergeFn>)

The output of a merge is determined by looking up the value for the given function and the given arguments in the egraph.

Old

Always return the old value for the given function.

New

Always return the new value for the given function.

Const(Value)

Always overwrite the new value for the given function with a constant. This is more useful as a “base case” in a more complicated merge function (e.g. one that clamps a value between 1 and 100) than it is as a standalone merge function.