code: public static BigDecimal exp(BigDecimal x, MathContext mathContext) {
  		checkMathContext(mathContext);
  		if (x.signum() == 0) {
  			return ONE;
  		}
  
  		return expIntegralFractional(x, mathContext);
  	}
docs: Calculates the natural exponent of {@link BigDecimal} x (e<sup>x</sup>).
  
  <p>See: <a href="http://en.wikipedia.org/wiki/Exponent">Wikipedia: Exponent</a></p>
  
  @param x the {@link BigDecimal} to calculate the exponent for
  @param mathContext the {@link MathContext} used for the result
  @return the calculated exponent {@link BigDecimal} with the precision specified in the <code>mathContext</code>
  @throws UnsupportedOperationException if the {@link MathContext} has unlimited precision