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The [[glyph]] '''dot''' or '''period''' refers to the <code>.</code> character. It represents several unrelated concepts, some derived from traditional mathematical notation. The dot is one of the most [[wikipedia:Operator_overloading|overloaded]] APL symbols: | The [[glyph]] '''dot''' or '''period''' refers to the <code>.</code> character. It represents several unrelated concepts, some derived from traditional mathematical notation. The dot is one of the most [[wikipedia:Operator_overloading|overloaded]] APL symbols: | ||
* In all dialects, it is used as [[wikipedia:decimal separator|decimal separator]], for example < | * In all dialects, it is used as [[wikipedia:decimal separator|decimal separator]], for example <syntaxhighlight lang=apl inline>3.14</syntaxhighlight> representing <math>3+\tfrac{14}{100}</math>. | ||
* In all dialects, it is a [[dyadic operator]] with function [[operand]]s, deriving a [[dyadic function]] (< | * In all dialects, it is a [[dyadic operator]] with function [[operand]]s, deriving a [[dyadic function]] (<syntaxhighlight lang=apl inline>X f.g Y</syntaxhighlight>) which is the generalised [[Inner Product]]. Specifically, <syntaxhighlight lang=apl inline>X +.× Y</syntaxhighlight> is the [[wikipedia:dot product|dot product]]. | ||
* In all dialects (although deprecated in [[SAX]]), dot with a [[Jot]] on on its left, forms the [[Outer Product]] operator. | * In all dialects (although deprecated in [[SAX]]), dot with a [[Jot]] on on its left, forms the [[Outer Product]] operator. | ||
* In [[SHARP APL]] and [[NARS2000]], the function derived from two functions operands, can also be called [[monadic function|monadically]] and then represents the [[Alternant]] (< | * In [[SHARP APL]] and [[NARS2000]], the function derived from two functions operands, can also be called [[monadic function|monadically]] and then represents the [[Alternant]] (<syntaxhighlight lang=apl inline>+.× Y</syntaxhighlight>) which is a generalisation of [[wikipedia:determinant|determinant]]s and [[wikipedia:permanent|permanent]]s. Specifically, <syntaxhighlight lang=apl inline>-.× Y</syntaxhighlight> is the [[wikipedia:determinant|determinant]]. | ||
* In [[SHARP APL]], with a function left operand and an array right operand, called ''ply'', is used for the [[Power Operator]] (< | * In [[SHARP APL]], with a function left operand and an array right operand, called ''ply'', is used for the [[Power Operator]] (<syntaxhighlight lang=apl inline>f⍣k</syntaxhighlight> in several other dialects). | ||
* In dialects that support [[object oriented programming]], for example [[APLX]] and [[Dyalog APL]], the dot is used to access members of objects. | * In dialects that support [[object oriented programming]], for example [[APLX]] and [[Dyalog APL]], the dot is used to access members of objects. | ||
* In [[NARS2000]], two immediately adjacent dots, < | * In [[NARS2000]], two immediately adjacent dots, <syntaxhighlight lang=apl inline>..</syntaxhighlight>, form a [[bi-glyph]], and represents the [[Sequence]] function (represented by the ellipsis, <syntaxhighlight lang=apl inline>…</syntaxhighlight> in [[dzaima/APL]] and [[Extended Dyalog APL]]). | ||
Due to its use in numeric constants, letting < | Due to its use in numeric constants, letting <syntaxhighlight lang=apl inline>.</syntaxhighlight> be a dyadic operator that takes numeric operands or a function that takes numeric arguments, is potentially problematic or at least confusing: | ||
< | <syntaxhighlight lang=apl> | ||
4.6 | 4.6 | ||
4.6 | 4.6 |