First: Difference between revisions

{{Built-ins|First|x|↑}} is a [[monadic function]] which extracts the first [[element]] in [[ravel order]] from its argument, or, if the argument is [[empty]], returns its [[prototype]]. In a [[Nested array model|nested]] APL, First reduces the positive [[depth]] of an argument other than a [[simple scalar]] by at least one; in a [[Flat array model|flat]] APL it does not change the depth. A flat array language may also use the [[Head]] function to get the first [[major cell]] of its argument rather than the first 0-[[cell]]. In this case First can be obtained by taking the Head of the [[Ravel]] of the argument.