Up Arrow

The glyph up arrow (or pike, in A Dictionary of APL) is an upwards pointing arrow represented by the Unicode character, "upwards arrow". The up arrow has several uses in various dialects:
 * In all dialects,  is Take when used dyadically (except very early versions of APL\360, which used it for Rotate).
 * In SHARP APL,  is Nub when monadic.
 * In APL2, NARS2000, GNU APL, and APLX,  is First when monadic.
 * In Dyalog APL, dzaima/APL, and ngn/apl,  is Mix when monadic.
 * In A+,  is Signal, giving an error with the specified message, when monadic.