Arithmetic represents a node where the result is arithmetic of two or more operands in the order given.

BasicScope is a simple scope that looks up variables and functions using a map.

Call represents a function call.

Concat represents a node where the result of two or more expressions are concatenated.

Function defines a function that can be executed by the engine.

LiteralNode represents a single literal value, such as "foo" or 42 or 3.14159.

Pos is the starting position of an AST node.

Stack is a stack of Node.

Variable is a variable value for execution given as input to the engine.

VariableAccess represents a variable access.

Node is the interface that all AST nodes must implement.

Scope is the interface used to look up variables and functions while evaluating.

ArithmeticOp is the operation to use for the math.

Type is the type of any value.

Visitors are just implementations of this function.