SIMD signals need to_signed and to_unsigned which can be implemented in terms of an Assign to the alternate type.
commit 90ad7e29637c953efe536a11e55215be2d3e3d98 (HEAD -> master) Author: Luke Kenneth Casson Leighton <lkcl@lkcl.net> Date: Tue Oct 5 17:42:43 2021 +0100 add signed/unsigned functions and preliminary unit test needs a better test.