nativemath.java

這是一個javascript 的 interpreter是了解 web browser的好材料

                    }
                }
                break;

            case Id_pow:
                x = ScriptRuntime.toNumber(args, 0);
                x = js_pow(x, ScriptRuntime.toNumber(args, 1));
                break;

            case Id_random:
                x = Math.random();
                break;

            case Id_round:
                x = ScriptRuntime.toNumber(args, 0);
                if (x == x && x != Double.POSITIVE_INFINITY
                    && x != Double.NEGATIVE_INFINITY)
                {
                    // Round only finite x
                    long l = Math.round(x);
                    if (l != 0) {
                        x = l;
                    } else {
                        // We must propagate the sign of d into the result
                        if (x < 0.0) {
                            x = ScriptRuntime.negativeZero;
                        } else if (x != 0.0) {
                            x = 0.0;
                        }
                    }
                }
                break;

            case Id_sin:
                x = ScriptRuntime.toNumber(args, 0);
                x = (x == Double.POSITIVE_INFINITY
                     || x == Double.NEGATIVE_INFINITY)
                    ? Double.NaN : Math.sin(x);
                break;

            case Id_sqrt:
                x = ScriptRuntime.toNumber(args, 0);
                x = Math.sqrt(x);
                break;

            case Id_tan:
                x = ScriptRuntime.toNumber(args, 0);
                x = Math.tan(x);
                break;

            default: throw new IllegalStateException(String.valueOf(methodId));
        }
        return ScriptRuntime.wrapNumber(x);
    }

    // See Ecma 15.8.2.13
    private double js_pow(double x, double y) {
        double result;
        if (y != y) {
            // y is NaN, result is always NaN
            result = y;
        } else if (y == 0) {
            // Java's pow(NaN, 0) = NaN; we need 1
            result = 1.0;
        } else if (x == 0) {
            // Many dirrerences from Java's Math.pow
            if (1 / x > 0) {
                result = (y > 0) ? 0 : Double.POSITIVE_INFINITY;
            } else {
                // x is -0, need to check if y is an odd integer
                long y_long = (long)y;
                if (y_long == y && (y_long & 0x1) != 0) {
                    result = (y > 0) ? -0.0 : Double.NEGATIVE_INFINITY;
                } else {
                    result = (y > 0) ? 0.0 : Double.POSITIVE_INFINITY;
                }
            }
        } else {
            result = Math.pow(x, y);
            if (result != result) {
                // Check for broken Java implementations that gives NaN
                // when they should return something else
                if (y == Double.POSITIVE_INFINITY) {
                    if (x < -1.0 || 1.0 < x) {
                        result = Double.POSITIVE_INFINITY;
                    } else if (-1.0 < x && x < 1.0) {
                        result = 0;
                    }
                } else if (y == Double.NEGATIVE_INFINITY) {
                    if (x < -1.0 || 1.0 < x) {
                        result = 0;
                    } else if (-1.0 < x && x < 1.0) {
                        result = Double.POSITIVE_INFINITY;
                    }
                } else if (x == Double.POSITIVE_INFINITY) {
                    result = (y > 0) ? Double.POSITIVE_INFINITY : 0.0;
                } else if (x == Double.NEGATIVE_INFINITY) {
                    long y_long = (long)y;
                    if (y_long == y && (y_long & 0x1) != 0) {
                        // y is odd integer
                        result = (y > 0) ? Double.NEGATIVE_INFINITY : -0.0;
                    } else {
                        result = (y > 0) ? Double.POSITIVE_INFINITY : 0.0;
                    }
                }
            }
        }
        return result;
    }

// #string_id_map#

    protected int findPrototypeId(String s)
    {
        int id;
// #generated# Last update: 2004-03-17 13:51:32 CET
        L0: { id = 0; String X = null; int c;
            L: switch (s.length()) {
            case 1: if (s.charAt(0)=='E') {id=Id_E; break L0;} break L;
            case 2: if (s.charAt(0)=='P' && s.charAt(1)=='I') {id=Id_PI; break L0;} break L;
            case 3: switch (s.charAt(0)) {
                case 'L': if (s.charAt(2)=='2' && s.charAt(1)=='N') {id=Id_LN2; break L0;} break L;
                case 'a': if (s.charAt(2)=='s' && s.charAt(1)=='b') {id=Id_abs; break L0;} break L;
                case 'c': if (s.charAt(2)=='s' && s.charAt(1)=='o') {id=Id_cos; break L0;} break L;
                case 'e': if (s.charAt(2)=='p' && s.charAt(1)=='x') {id=Id_exp; break L0;} break L;
                case 'l': if (s.charAt(2)=='g' && s.charAt(1)=='o') {id=Id_log; break L0;} break L;
                case 'm': c=s.charAt(2);
                    if (c=='n') { if (s.charAt(1)=='i') {id=Id_min; break L0;} }
                    else if (c=='x') { if (s.charAt(1)=='a') {id=Id_max; break L0;} }
                    break L;
                case 'p': if (s.charAt(2)=='w' && s.charAt(1)=='o') {id=Id_pow; break L0;} break L;
                case 's': if (s.charAt(2)=='n' && s.charAt(1)=='i') {id=Id_sin; break L0;} break L;
                case 't': if (s.charAt(2)=='n' && s.charAt(1)=='a') {id=Id_tan; break L0;} break L;
                } break L;
            case 4: switch (s.charAt(1)) {
                case 'N': X="LN10";id=Id_LN10; break L;
                case 'c': X="acos";id=Id_acos; break L;
                case 'e': X="ceil";id=Id_ceil; break L;
                case 'q': X="sqrt";id=Id_sqrt; break L;
                case 's': X="asin";id=Id_asin; break L;
                case 't': X="atan";id=Id_atan; break L;
                } break L;
            case 5: switch (s.charAt(0)) {
                case 'L': X="LOG2E";id=Id_LOG2E; break L;
                case 'S': X="SQRT2";id=Id_SQRT2; break L;
                case 'a': X="atan2";id=Id_atan2; break L;
                case 'f': X="floor";id=Id_floor; break L;
                case 'r': X="round";id=Id_round; break L;
                } break L;
            case 6: c=s.charAt(0);
                if (c=='L') { X="LOG10E";id=Id_LOG10E; }
                else if (c=='r') { X="random";id=Id_random; }
                break L;
            case 7: X="SQRT1_2";id=Id_SQRT1_2; break L;
            case 8: X="toSource";id=Id_toSource; break L;
            }
            if (X!=null && X!=s && !X.equals(s)) id = 0;
        }
// #/generated#
        return id;
    }

    private static final int
        Id_toSource     =  1,
        Id_abs          =  2,
        Id_acos         =  3,
        Id_asin         =  4,
        Id_atan         =  5,
        Id_atan2        =  6,
        Id_ceil         =  7,
        Id_cos          =  8,
        Id_exp          =  9,
        Id_floor        = 10,
        Id_log          = 11,
        Id_max          = 12,
        Id_min          = 13,
        Id_pow          = 14,
        Id_random       = 15,
        Id_round        = 16,
        Id_sin          = 17,
        Id_sqrt         = 18,
        Id_tan          = 19,

        LAST_METHOD_ID  = 19;

    private static final int
        Id_E            = LAST_METHOD_ID + 1,
        Id_PI           = LAST_METHOD_ID + 2,
        Id_LN10         = LAST_METHOD_ID + 3,
        Id_LN2          = LAST_METHOD_ID + 4,
        Id_LOG2E        = LAST_METHOD_ID + 5,
        Id_LOG10E       = LAST_METHOD_ID + 6,
        Id_SQRT1_2      = LAST_METHOD_ID + 7,
        Id_SQRT2        = LAST_METHOD_ID + 8,

        MAX_ID = LAST_METHOD_ID + 8;

// #/string_id_map#
}