 Diamond operator

Multiplication of a marked point by a unit modulo $N$ gives the diamond action. In modular coordinates this is the slash action of a lift in ${\Gamma }_0(N)$ with lower-right entry $d$. Its Dirichlet character eigenspaces give nebentypus modular forms. For a nonzero form, the action of $-1$ imposes $\chi (-1)=(-1{)}^k$.

The "Diamond Operator" often refers to two different concepts in programming and computer science, depending on the context: 1. **In Java Generics**: The Diamond Operator (`<>`) was introduced in Java 7 to simplify the use of generics.