{. and {: Extended |
initial writing: 2001-10-22 last updated: 2001-10-30 |
{.y ↔ 0{ 1{.y {:y ↔ 0{_1{.yTherefore, {.y gives the first item of y , or an item of fills if y has no items; likewise {:y gives the last item, or fills if y has no items. {.!.f and {:!.f specify that the fill should be the atom f .