How to mark expression to skip or use variable names?

[DktPhl2019]

Hello

For example, I have math expression: 21+5*(e^(-1))+log(8)-9-(2^3)/6

exp = Expression("21+5*(e^(-1))+log(8)-9+(2^3)/6").eval().toString();

I know the following:

a = 21
b = 5*(e^(-1))
c = log(8)-9
d = (2^3)/6

Ideally, I want to evaluate the expression using variable names: a+b+c-d

exp = Expression(a+b+c-d).eval().toString();

I know it is not currently possible to use variables in eval expression.

I wonder if I somehow skip symbols like this: 'a:'+21+'b:'+5*(e^(-1))+'c:'+log(8)-9+'d:'+(2^3)/6

Could you please let me know your thoughts.

Thank You

[widavies]

Little busy, will get to this when I have a chance, thanks for your patience!

[widavies]

@DktPhl2019 Did you try the example by setting variables using setStringVariable?

Expression exp = Expression("2 ^ 4 + 8");
  print(exp.eval().toString()); // 24

  // With a variable
  exp = Expression("a ^ b + c");
  // Variables may contain alphanumeric characters, and "_". This can be changed
  // by using setVariableCharacters(..) and setFirstVariableCharacters(..) (what chars variable are allowed to start with).
  exp.setStringVariable("a", "2");
  exp.setStringVariable("b", "4");
  exp.setStringVariable("c", "8");
  print(exp.eval().toString()); // 24