In reply to atashinchi:
a[->2]
is the same as
(!a[*0:$] ##1 a) [*2]
is the same as
!a[*0:$] ##1 a ##1 !a[*0:$] ##1 a
In reply to atashinchi:
a[->2]
is the same as
(!a[*0:$] ##1 a) [*2]
is the same as
!a[*0:$] ##1 a ##1 !a[*0:$] ##1 a