# Today I Learned

Some of the things I've learned every day since Oct 10, 2016

## 94: The Liskov Substitution Principle

The Liskov Substitution Principle makes the intuitive generalization that if $A, B$ are types and $A <: B$ ($A$ is a subtype of $B$), then in a program with this type system, objects from $B$ can be substituted with objects from $A$ without certain properties of the program being affected.