signExtend

Sign extend variable bit-width integer. 📰 📘

signExtend x w
-- x: variable bit-width integer
-- w: bit width (32)

import Bit exposing (..)

signExtend 15 4
-- -1 (1111 ⇒ -1)

signExtend 3 3
-- 3  (011 ⇒ 3)

signExtend 4 3
-- -4 (100 ⇒ -4)

References

• Bit Twiddling Hacks, By Sean Eron Anderson
• Sign extension
• Variable-length quantity