# AST Structure
A tree is any of the following:
- An integer
- A decimal
- TODO: support a number in scientific notation
- A free variable (this can include greek letters/subscripts)
- TBD list of non-variable symbols to leave (ellipses, infinity, DNE)
- One of the following binary expressions:
- Addition
- Subtraction
- Multiplication
- Division
- Exponentiation
- Logarithms
- Modulo
- Any of the binary comparison relations ≤, ≥, <, >, =, ≠, ~
- The improper and proper subset relations
- Logical and, or, xor, and implication (this last one also serving as a general arrow between two equations)
- One of the following unary expressions:
- The unary minus and plus operator
- The logical not operator
- TODO: possible display control might go here (bold, strikethrough, italic, etc.)
- A function with any amount of arguments