examples for: A is mapping reducible to B but B is not mapping reducible to A I find it hard to find reductions that only work on one side:
A is mapping reducible to B, but B is not mapping reducible to A.
what could be an easy way to find such two languages A,B ?
I tried Atm,Htm,EQtm,Etm,RegTm, and many others, and whenever I found that A is reducable to B, I also found that B is reducable to A.

thanks.
I now understand that there is a mapping reduction from the empty language to any other language except Sigma*, and there cannot be a reduction from a language to the empty language except for a reduction from the empty language to the empty language.