f:{{x@0,x@1,x@2}" "\x}
f:{{x@0,x@1,x@2}/" "\x}
"0123456789abcdef"@16\
@
@[1 2 3 4 5;1 3;:;3 5]
1 2 3 4 5
1 3
3 5
?[x;y;z] splice ?["abcd";1 3;"xyz"] -> "axyzd"