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version 2.080.0

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Struct std.bitmanip.DoubleRep

Allows manipulating the fraction, exponent, and sign parts of a double separately. The definition is:

struct DoubleRep ; 
struct DoubleRep
{
    union
    {
        double value;
        mixin(bitfields!(
                  ulong,   "fraction", 52,
                  ushort,  "exponent", 11,
                  bool,    "sign",      1));
    }
    enum uint bias = 1023, signBits = 1, fractionBits = 52, exponentBits = 11;
}

Example

DoubleRep rep = {value: 0};
writeln(rep.fraction); // 0
writeln(rep.exponent); // 0
assert(!rep.sign);

rep.value = 42;
writeln(rep.fraction); // 1407374883553280
writeln(rep.exponent); // 1028
assert(!rep.sign);

rep.value = 10;
writeln(rep.fraction); // 1125899906842624
writeln(rep.exponent); // 1026

Example

DoubleRep rep = {value: 1};
writeln(rep.fraction); // 0
writeln(rep.exponent); // 1023
assert(!rep.sign);

rep.exponent = 1022;
writeln(rep.value); // 0.5

rep.exponent = 1026;
writeln(rep.value); // 8

Example

DoubleRep rep = {value: 1};
rep.value = -0.5;
writeln(rep.fraction); // 0
writeln(rep.exponent); // 1022
assert(rep.sign);

rep.value = -1. / 3;
writeln(rep.fraction); // 1501199875790165
writeln(rep.exponent); // 1021
assert(rep.sign);

Example

Reading 

DoubleRep x;
x.value = 1.0;
assert(x.fraction == 0 && x.exponent == 1023 && !x.sign);
x.value = -0.5;
assert(x.fraction == 0 && x.exponent == 1022 && x.sign);
x.value = 0.5;
assert(x.fraction == 0 && x.exponent == 1022 && !x.sign);

Example

Writing 

DoubleRep x;
x.fraction = 1125899906842624;
x.exponent = 1025;
x.sign = true;
writeln(x.value); // -5.0

Authors

Walter Bright, Andrei Alexandrescu, Jonathan M Davis, Alex Rønne Petersen, Damian Ziemba, Amaury SECHET

License

Boost License 1.0.