Index - U
| uncons | Protolude |
| uncurry | Protolude |
| undefined | Protolude |
| UndefinedElement | Protolude |
| Underflow | Protolude |
| unGetChan | Protolude |
| uninterruptibleMask | Protolude |
| uninterruptibleMask_ | Protolude |
| unless | Protolude |
| unlessM | Protolude |
| Unmasked | Protolude |
| unsafeHead | Unsafe |
| unsafeIndex | Unsafe |
| unsafeInit | Unsafe |
| unsafeLast | Unsafe |
| unsafeShiftL | Protolude |
| unsafeShiftR | Protolude |
| unsafeTail | Unsafe |
| UserInterrupt | Protolude |