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The [[glyph]] '''del''' is a triangular symbol resembling an inverted Greek [[wikipedia:delta (letter)|delta]] and is represented by the [[Unicode]] character <code>∇</code>, "nabla". Its uses include: | The [[glyph]] '''del''' is a triangular symbol resembling an inverted Greek [[wikipedia:delta (letter)|delta]] and is represented by the [[Unicode]] character <code>∇</code>, "nabla". Its uses include: | ||
* In [[APL\360]] and most other APLs, it is used to enter and exit the [[wikipedia:line editor]] which provides a function definition mode.<ref>[[Dyalog Ltd.]] Programming Reference Guide. [https://help.dyalog.com/latest/#Language/Defined%20Functions%20and%20Operators/APL%20Line%20Editor.htm APL Line Editor].</ref> | * In [[APL\360]] and most other APLs, it is used to enter and exit the [[wikipedia:line editor]] which provides a function definition mode.<ref>[[Dyalog Ltd.]] Programming Reference Guide. [https://help.dyalog.com/latest/#Language/Defined%20Functions%20and%20Operators/APL%20Line%20Editor.htm APL Line Editor].</ref> | ||
* In [[Dyalog APL]], [[NARS2000]], [[ngn/ | * In [[Dyalog APL]], [[NARS2000]], [[ngn/apl]], and [[dzaima/APL]] <source lang=apl inline>∇</source> represents the current [[dfn]], or the function derived from the current [[dop]], such that anonymous functions and operators may [[wikipedia:recursion (computer science)|recurse]].<ref>[[Dyalog Ltd.]] Programming Reference Guide. [https://help.dyalog.com/latest/#Language/Defined%20Functions%20and%20Operators/DynamicFunctions/Recursion.htm Recursion].</ref> | ||
* In [[Dyalog APL]], <source lang=apl inline>∇</source> is used to delimit [[tradfn]] members of scripted [[object oriented programming|objects]].<ref>[[Dyalog Ltd.]] Programming Reference Guide. [https://help.dyalog.com/latest/#Language/Object%20Oriented%20Programming/Class%20Members/Methods/Methods.htm Methods].</ref> | * In [[Dyalog APL]], <source lang=apl inline>∇</source> is used to delimit [[tradfn]] members of scripted [[object oriented programming|objects]].<ref>[[Dyalog Ltd.]] Programming Reference Guide. [https://help.dyalog.com/latest/#Language/Object%20Oriented%20Programming/Class%20Members/Methods/Methods.htm Methods].</ref> | ||
* In [[APL2]], [[APLX]], and [[APL*PLUS]], a variant glyph <source lang=apl inline>⍫</source>, consisting of a Del <source lang=apl inline>∇</source> overstruck with a Tilde <source lang=apl inline>~</source>, is used instead of the closing <source lang=apl inline>∇</source> to "lock" the function definition. This prevents viewing or modifying the function's definition while still allowing the function to run. <ref>[[MicroAPL]]. APLX Help. [http://microapl.com/apl_help/ch_020_010_070.htm User-defined Functions].</ref> [[Dyalog APL]] instead offers the [[Lock Definition]] (<source lang=apl inline>⎕LOCK</source>) [[system function]] which provides a more fine-grained management of locked behaviour.<ref>[[Dyalog Ltd.]] Language Reference Guide. [https://help.dyalog.com/latest/#Language/System%20Functions/lock.htmLock Definition].</ref> | * In [[APL2]], [[APLX]], and [[APL*PLUS]], a variant glyph <source lang=apl inline>⍫</source>, consisting of a Del <source lang=apl inline>∇</source> overstruck with a Tilde <source lang=apl inline>~</source>, is used instead of the closing <source lang=apl inline>∇</source> to "lock" the function definition. This prevents viewing or modifying the function's definition while still allowing the function to run. <ref>[[MicroAPL]]. APLX Help. [http://microapl.com/apl_help/ch_020_010_070.htm User-defined Functions].</ref> [[Dyalog APL]] instead offers the [[Lock Definition]] (<source lang=apl inline>⎕LOCK</source>) [[system function]] which provides a more fine-grained management of locked behaviour.<ref>[[Dyalog Ltd.]] Language Reference Guide. [https://help.dyalog.com/latest/#Language/System%20Functions/lock.htmLock Definition].</ref> | ||
Revision as of 20:30, 24 November 2020
∇
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The glyph del is a triangular symbol resembling an inverted Greek delta and is represented by the Unicode character ∇, "nabla". Its uses include:
- In APL\360 and most other APLs, it is used to enter and exit the wikipedia:line editor which provides a function definition mode.[1]
- In Dyalog APL, NARS2000, ngn/apl, and dzaima/APL
∇represents the current dfn, or the function derived from the current dop, such that anonymous functions and operators may recurse.[2] - In Dyalog APL,
∇is used to delimit tradfn members of scripted objects.[3] - In APL2, APLX, and APL*PLUS, a variant glyph
⍫, consisting of a Del∇overstruck with a Tilde~, is used instead of the closing∇to "lock" the function definition. This prevents viewing or modifying the function's definition while still allowing the function to run. [4] Dyalog APL instead offers the Lock Definition (⎕LOCK) system function which provides a more fine-grained management of locked behaviour.[5] - In APL*PLUS,
⍝∇marks a special "public comment" which can be retrieved with a dedicated system function even when the function is locked. This is also used to distinguish internal documentation from other comments.
It should be noted that Del (∇) has no connection to Delta (∆) other than visual similarity. The latter is treated as a normal identifier character in all respects.
References
- ↑ Dyalog Ltd. Programming Reference Guide. APL Line Editor.
- ↑ Dyalog Ltd. Programming Reference Guide. Recursion.
- ↑ Dyalog Ltd. Programming Reference Guide. Methods.
- ↑ MicroAPL. APLX Help. User-defined Functions.
- ↑ Dyalog Ltd. Language Reference Guide. Definition.
| APL glyphs [edit] | |
|---|---|
| Information | Glyph ∙ Typing glyphs (on Linux) ∙ Unicode ∙ Fonts ∙ Mnemonics ∙ Overstrikes ∙ Migration level |
| Individual glyphs | Jot (∘) ∙ Right Shoe (⊃) ∙ Up Arrow (↑) ∙ Zilde (⍬) ∙ High minus (¯) ∙ Dot (.) ∙ Del (∇)
|