abs() in awk command

It has been very annoying that there is no intrinsic absolute function in awk, but it's still easy to do it by ourself:

$ paste tmp1/energy.txt tmp2/energy.txt tmp3/energy.txt tmp4/energy.txt \
? | awk 'function abs(x){return (((x < 0.0) ? -x : x) + 0.0)}\
? {printf "%s %25.12f %25.12f %25.12f %25.12f\n", $1,\
? abs($2-$2),abs($4-$2),abs($6-$2),abs($8-$2)}'