↑) 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 |
|Monadic||Conjugate ∙ Not ∙ Roll ∙ Type|
|Dyadic||Plus ∙ Equal to (Xnor) ∙ Not Equal to (Xor)|
|Structural||Shape ∙ Reshape ∙ Depth ∙ Ravel ∙ Reverse|
|Selection||Take ∙ Drop ∙ Unique|
|Constants||Index origin ∙ Migration level|
|Other||Zilde ∙ High minus|