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{{Infobox terminology
{| class=vertical-navbox style="float:right; font-size:500%; margin:0 1ex;"
| title = {{Icon|⊃}} {{Icon|↑}}
|<code>⊃</code> <code>↑</code>
| en = First, [[Disclose]]
|}
}}
'''First''' (<code>⊃</code> or <code>↑</code> and also called '''[[Disclose]]''') is a [[monadic function]] in [[Nested array model|nested]] APLs 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 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 [[take|taking]] the Head of the [[Ravel]] of the argument.
'''First''' is a [[monadic function]] in [[Nested array model|nested]] APLs 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 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 [[take|taking]] the Head of the [[Ravel]] of the argument.


== External links ==
== External links ==
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=== Documentation ===
=== Documentation ===


* [https://help.dyalog.com/18.0/#Language/Primitive%20Functions/Disclose.htm Dyalog] (<source lang=apl inline>⊃</source>)
* [https://help.dyalog.com/18.0/#Language/Primitive%20Functions/Disclose.htm Dyalog] (<syntaxhighlight lang=apl inline>⊃</syntaxhighlight>)
* [http://microapl.com/apl_help/ch_020_020_550.htm APLX] (<source lang=apl inline>↑</source>)
* [http://microapl.com/apl_help/ch_020_020_550.htm APLX] (<syntaxhighlight lang=apl inline>↑</syntaxhighlight>)
* [https://mlochbaum.github.io/BQN/doc/pick.html#first BQN]
 
== See also ==
== See also ==
* [[Mix]]
* [[Mix]]
* [[Right Shoe]]
* [[Right Shoe]]
{{APL built-ins}}[[Category:Primitive functions]]
{{APL built-ins}}[[Category:Primitive functions]]

Latest revision as of 21:59, 10 September 2022

⊃ ↑

First (⊃ or ↑ and also called Disclose) is a monadic function in nested APLs 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.

External links

Lessons

Documentation

See also

APL built-ins [edit]
Primitives (Timeline) Functions
Scalar
Monadic Conjugate ∙ Negate ∙ Signum ∙ Reciprocal ∙ Magnitude ∙ Exponential ∙ Natural Logarithm ∙ Floor ∙ Ceiling ∙ Factorial ∙ Not ∙ Pi Times ∙ Roll ∙ Type ∙ Imaginary ∙ Square Root ∙ Round
Dyadic Add ∙ Subtract ∙ Times ∙ Divide ∙ Residue ∙ Power ∙ Logarithm ∙ Minimum ∙ Maximum ∙ Binomial ∙ Comparison functions ∙ Boolean functions (And, Or, Nand, Nor) ∙ GCD ∙ LCM ∙ Circular ∙ Complex ∙ Root
Non-Scalar
Structural Shape ∙ Reshape ∙ Tally ∙ Depth ∙ Ravel ∙ Enlist ∙ Table ∙ Catenate ∙ Reverse ∙ Rotate ∙ Transpose ∙ Raze ∙ Mix ∙ Split ∙ Enclose ∙ Nest ∙ Cut (K) ∙ Pair ∙ Link ∙ Partitioned Enclose ∙ Partition
Selection First ∙ Pick ∙ Take ∙ Drop ∙ Unique ∙ Identity ∙ Stop ∙ Select ∙ Replicate ∙ Expand ∙ Set functions (Intersection ∙ Union ∙ Without) ∙ Bracket indexing ∙ Index ∙ Cartesian Product ∙ Sort
Selector Index generator ∙ Grade ∙ Index Of ∙ Interval Index ∙ Indices ∙ Deal ∙ Prefix and suffix vectors
Computational Match ∙ Not Match ∙ Membership ∙ Find ∙ Nub Sieve ∙ Encode ∙ Decode ∙ Matrix Inverse ∙ Matrix Divide ∙ Format ∙ Execute ∙ Materialise ∙ Range
Operators Monadic Each ∙ Commute ∙ Constant ∙ Replicate ∙ Expand ∙ Reduce ∙ Windowed Reduce ∙ Scan ∙ Outer Product ∙ Key ∙ I-Beam ∙ Spawn ∙ Function axis ∙ Identity (Null, Ident)
Dyadic Bind ∙ Compositions (Compose, Reverse Compose, Beside, Withe, Atop, Over) ∙ Inner Product ∙ Determinant ∙ Power ∙ At ∙ Under ∙ Rank ∙ Depth ∙ Variant ∙ Stencil ∙ Cut ∙ Direct definition (operator) ∙ Identity (Lev, Dex)
Quad names Index origin ∙ Comparison tolerance ∙ Migration level ∙ Atomic vector
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