Pyret is not pure. We have mutation. But mutation has its own syntax different from regular binding. Variables (as opposed to identifiers) are preceded by "var"

Pyret is not pure. We have mutation. But mutation has its own syntax different from regular binding. Variables (as opposed to identifiers) are preceded by "var", and variable mutation uses ":=". [Similarly for fields.] This it to make clear to all forms of readers -- programmers, compilers, IDEs -- when something is mutable.