toSigned method
Returns the least significant width
bits of this integer, extending the
highest retained bit to the sign. This is the same as truncating the
value to fit in width
bits using an signed 2-s complement
representation.
The returned value has the same bit value in all positions higher than
width
.
V--sign bit-V
16.toSigned(5) == -16 // 00010000 -> 11110000
239.toSigned(5) == 15 // 11101111 -> 00001111
^ ^
This operation can be used to simulate arithmetic from low level languages. For example, to increment an 8 bit signed quantity:
q = (q + 1).toSigned(8);
q
will count from 0
up to 127
, wrap to -128
and count back up to
127
.
If the input value fits in width
bits without truncation, the result is
the same as the input. The minimum width needed to avoid truncation
of x
is x.bitLength + 1
, i.e.
x == x.toSigned(x.bitLength + 1);
Implementation
int toSigned(int width) => value.toSigned(width);