Expression building failing with leading numbers in variable name

[apoorv-28]

Expression : 1*2a

Error: Unknown function or variable 'a' at pos 3 in expression '1*2a'

Code:

val map = Map("2a" -> 0.1)
val expressionBuilder = new ExpressionBuilder("1*2a")
  .variables(map.keys.toList: _*)
  .build

Is this not supported or is it a probable bug?

[seyfahni]

It is currently not supported: https://www.objecthunter.net/exp4j/#Variable_declaration

Variable names must start with a letter or the underscore

[Kris-kun]

Well, propably because someting like "2a" is mathematically correct when "a" is a variable ("2a" = "2*a"). So if you had a variable "a" and "2a", the expression couldn't be compiled because it doesn't know which to use ("2a" as a variable or two times "a").