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First (, ) is a monadic function which extracts the first element in ravel order from its argument, or, if the argument is empty, returns its prototype. The glyph used varies by dialect. In a nested APL, First reduces the positive depth of an argument other than a simple scalar by at least one; in a 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.

APL built-ins [edit]
Primitive functions
Monadic ConjugateNotRollType
Dyadic AddSubtractEqual to (Xnor) ∙ Not Equal to (Xor)
Structural ShapeReshapeTallyDepthRavelReverseRazeMixCut (K)
Selection TakeDropUniqueIdentity
Selector Interval Index
Computational MatchNot MatchNub Sieve
Primitive operators Each
Quad names
Arrays Index originMigration level
Other ZildeHigh minusFunction axis