public static Dfp pow()

in commons-math-legacy-core/src/main/java/org/apache/commons/math4/legacy/core/dfp/DfpMath.java [500:657]
121 lines of code
40 McCabe index (conditional complexity)

    public static Dfp pow(Dfp x, final Dfp y) {

        // make sure we don't mix number with different precision
        if (x.getField().getRadixDigits() != y.getField().getRadixDigits()) {
            x.getField().setIEEEFlagsBits(DfpField.FLAG_INVALID);
            final Dfp result = x.newInstance(x.getZero());
            result.nans = Dfp.QNAN;
            return x.dotrap(DfpField.FLAG_INVALID, POW_TRAP, x, result);
        }

        final Dfp zero = x.getZero();
        final Dfp one  = x.getOne();
        final Dfp two  = x.getTwo();
        boolean invert = false;
        int ui;

        /* Check for special cases */
        if (y.equals(zero)) {
            return x.newInstance(one);
        }

        if (y.equals(one)) {
            if (x.isNaN()) {
                // Test for NaNs
                x.getField().setIEEEFlagsBits(DfpField.FLAG_INVALID);
                return x.dotrap(DfpField.FLAG_INVALID, POW_TRAP, x, x);
            }
            return x;
        }

        if (x.isNaN() || y.isNaN()) {
            // Test for NaNs
            x.getField().setIEEEFlagsBits(DfpField.FLAG_INVALID);
            return x.dotrap(DfpField.FLAG_INVALID, POW_TRAP, x, x.newInstance((byte)1, Dfp.QNAN));
        }

        // X == 0
        if (x.equals(zero)) {
            if (Dfp.copySign(one, x).greaterThan(zero)) {
                // X == +0
                if (y.greaterThan(zero)) {
                    return x.newInstance(zero);
                } else {
                    return x.newInstance(x.newInstance((byte)1, Dfp.INFINITE));
                }
            } else {
                // X == -0
                if (y.classify() == Dfp.FINITE && y.rint().equals(y) && !y.remainder(two).equals(zero)) {
                    // If y is odd integer
                    if (y.greaterThan(zero)) {
                        return x.newInstance(zero.negate());
                    } else {
                        return x.newInstance(x.newInstance((byte)-1, Dfp.INFINITE));
                    }
                } else {
                    // Y is not odd integer
                    if (y.greaterThan(zero)) {
                        return x.newInstance(zero);
                    } else {
                        return x.newInstance(x.newInstance((byte)1, Dfp.INFINITE));
                    }
                }
            }
        }

        if (x.lessThan(zero)) {
            // Make x positive, but keep track of it
            x = x.negate();
            invert = true;
        }

        if (x.greaterThan(one) && y.classify() == Dfp.INFINITE) {
            if (y.greaterThan(zero)) {
                return y;
            } else {
                return x.newInstance(zero);
            }
        }

        if (x.lessThan(one) && y.classify() == Dfp.INFINITE) {
            if (y.greaterThan(zero)) {
                return x.newInstance(zero);
            } else {
                return x.newInstance(Dfp.copySign(y, one));
            }
        }

        if (x.equals(one) && y.classify() == Dfp.INFINITE) {
            x.getField().setIEEEFlagsBits(DfpField.FLAG_INVALID);
            return x.dotrap(DfpField.FLAG_INVALID, POW_TRAP, x, x.newInstance((byte)1, Dfp.QNAN));
        }

        if (x.classify() == Dfp.INFINITE) {
            // x = +/- inf
            if (invert) {
                // negative infinity
                if (y.classify() == Dfp.FINITE && y.rint().equals(y) && !y.remainder(two).equals(zero)) {
                    // If y is odd integer
                    if (y.greaterThan(zero)) {
                        return x.newInstance(x.newInstance((byte)-1, Dfp.INFINITE));
                    } else {
                        return x.newInstance(zero.negate());
                    }
                } else {
                    // Y is not odd integer
                    if (y.greaterThan(zero)) {
                        return x.newInstance(x.newInstance((byte)1, Dfp.INFINITE));
                    } else {
                        return x.newInstance(zero);
                    }
                }
            } else {
                // positive infinity
                if (y.greaterThan(zero)) {
                    return x;
                } else {
                    return x.newInstance(zero);
                }
            }
        }

        if (invert && !y.rint().equals(y)) {
            x.getField().setIEEEFlagsBits(DfpField.FLAG_INVALID);
            return x.dotrap(DfpField.FLAG_INVALID, POW_TRAP, x, x.newInstance((byte)1, Dfp.QNAN));
        }

        // End special cases

        Dfp r;
        if (y.lessThan(x.newInstance(100000000)) && y.greaterThan(x.newInstance(-100000000))) {
            final Dfp u = y.rint();
            ui = u.intValue();

            final Dfp v = y.subtract(u);

            if (v.unequal(zero)) {
                final Dfp a = v.multiply(log(x));
                final Dfp b = a.divide(x.getField().getLn2()).rint();

                final Dfp c = a.subtract(b.multiply(x.getField().getLn2()));
                r = splitPow(split(x), ui);
                r = r.multiply(pow(two, b.intValue()));
                r = r.multiply(exp(c));
            } else {
                r = splitPow(split(x), ui);
            }
        } else {
            // very large exponent.  |y| > 1e8
            r = exp(log(x).multiply(y));
        }

        if (invert && y.rint().equals(y) && !y.remainder(two).equals(zero)) {
            // if y is odd integer
            r = r.negate();
        }

        return x.newInstance(r);
    }