code: @Override
      public double compute(double a, double b) {
          this.function.getVariables().put("a", a);
          this.function.getVariables().put("b", b);
          return this.function.evaluate();
      }
docs: Computes the S-Norm utilizing the given function via
  SNormFunction::setFormula(), which automatically assigns the values of
  
  `a` and `b`.
  
  @param a is a membership function value
  @param b is a membership function value
  @return the evaluation of the function