Tokenizes an input stream to a list of Tokens

Arithmetic examples:

>>> scan "1+2"
Right [Number 1.0,Operator "+",Number 2.0]

>>> scan "(3/2+(1.5*2)) + 4.95"
Right [OpenParen,Number 3.0,Operator "/",Number 2.0,Operator "+",OpenParen,Number 1.5,Operator "*",Number 2.0,CloseParen,CloseParen,Operator "+",Number 4.95]

>>> scan "9001*29.12"
Right [Number 9001.0,Operator "*",Number 29.12]

Examples with units:

>>> scan "2km [m]"
Right [Number 2.0,Identifier "km",OpenBracket,Identifier "m",CloseBracket]

Examples with variables:

>>> scan "a = 3, b = 2 -> a + b"
Right [Identifier "a",Equal,Number 3.0,Comma,Identifier "b",Equal,Number 2.0,Arrow,Identifier "a",Operator "+",Identifier "b"]