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The advent of '''[[wikipedia:Unicode|Unicode]]''' solved many problems with dealing with APL [[glyph|character]]s, however there was still some wiggle room as to which Unicode [[wikipedia:code point|codepoint]] were to be used in a Unicode implementation of APL, and different implementors made different choices.  This article, which documents these differences, is adapted from an original paper by [[Bob Smith]]<ref>Smith, Bob. [http://www.sudleyplace.com/APL/APL%20Characters%20and%20Their%20Aliases.pdf APL Characters and Their Aliases]. 14 Dec 2013–25 Dec 2019. Sudley Place Software.</ref> that attempted to raise awareness of these issues because the differences impede transfer of information.
The advent of '''[[wikipedia:Unicode|Unicode]]''' solved many problems with dealing with APL [[glyph|character]]s, however there was still some wiggle room as to which Unicode [[wikipedia:code point|codepoint]] were to be used in a Unicode implementation of APL, and different implementors made different choices.  This article, which documents these differences, is adapted from an original paper by [[Bob Smith]]<ref>Smith, Bob. ''APL Characters and Their Aliases''. 14 Dec 2013–25 Dec 2019. Sudley Place Software.</ref> that attempted to raise awareness of these issues because the differences impede transfer of information.


The relevant document for the APL character set is the ''APL Character Repertoire'' (ACR)<ref>ISO-IEC/JTC1/SC22/WG3. [http://std.dkuug.dk/jtc1/sc22/open/n3067.pdf N3067]: APL Character Repertoire. 28 Dec 1999.</ref>. For whatever reasons, that document never became a standard, but it does provide some guidance, and is better than each implementor making separate choices.
The relevant document for the APL character set is the ''APL Character Repertoire'' (ACR)<ref>ISO-IEC/JTC1/SC22/WG3. [http://std.dkuug.dk/jtc1/sc22/open/n3067.pdf N3067]: APL Character Repertoire. 28 Dec 1999.</ref>. For whatever reasons, that document never became a standard, but it does provide some guidance, and is better than each implementor making separate choices.


==Introduction==
==Introduction==
There are a surprising number of similar APL characters in Unicode and in several cases some implementors went one way, others the other way.  The following table lists the characters in question, along with the way [[APL2]], [[Dyalog]], [[GNU APL]], [[NARS2000]], [[ngn/apl]], and [[dzaima/APL]] behave. APL2000 states that ''Generally the default codepoint scheme for the VisualAPL product follows the IBM APL2 workstation scheme''. Please [https://aplwiki.com/index.php?title=Unicode&action=edit edit] this page if you believe there are other characters that should be included in the table.
There are a surprising number of similar APL characters in Unicode and in several cases some implementors went one way, others the other way.  The following table lists the characters in question, along with the way [[APL2]], [[Dyalog]], [[GNU APL]], [[NARS2000]], [[ngn/apl]], and [[dzaima/APL]] behave. APL2000 states that ''Generally the default codepoint scheme for the VisualAPL product follows the IBM APL2 workstation scheme''. Please [https://aplwiki.com/index.php?title=Unicode&action=edit&section=2 edit] the table if you believe there are other characters that should be included in the table, or to add another dialect.


When there are differences among APL implementations, users can become confused. They type something into one APL system, copy it to another and are greeted by a [[SYNTAX ERROR]] or the like.
When there are differences among APL implementations, users can become confused. They type something into one APL system, copy it to another and are greeted by a [[SYNTAX ERROR]] or the like.


The whole basis for the confusion in a lengthy thread on comp.lang.apl entitled ''caret vs and''<ref>[https://groups.google.com/forum/#!forum/comp.lang.apl comp.lang.apl]. [https://groups.google.com/d/msg/comp.lang.apl/LTV-HTxEZI0/DAPcTrVPnmwJ caret vs and]. 28 Oct 2013&ndash;9 Dec 2013</ref> is that in some implementations the symbol for the logical [[And]] function is U+005E only, in some implementations it's U+2227 only, and in some both characters work. The original poster encountered some APL text from the [[APL Wiki]] that had been produced by a system that supports U+005E and copied it into a system that uses U+2227 only and fails on U+005E.
The whole basis for the confusion in a lengthy thread on comp.lang.apl entitled ''caret vs and''<ref>[https://groups.google.com/forum/#!forum/comp.lang.apl comp.lang.apl]. [https://groups.google.com/d/msg/comp.lang.apl/LTV-HTxEZI0/DAPcTrVPnmwJ caret vs and]. 28 Oct 2013&ndash;9 Dec 2013</ref> was that in some implementations the symbol for the logical [[And]] function was U+005E only, in some implementations it was U+2227 only, and in some both characters worked. The original poster encountered some APL text from the [[APL Wiki]] that had been produced by a system that supports U+005E and copied it into a system that used U+2227 only and failed on U+005E.


When our systems differ in the set of acceptable characters for the same function, it serves only to confuse the end user to the detriment of the community.
When systems differ in the set of acceptable characters for the same function, it serves only to confuse the end user to the detriment of the community. The cautious APL programmer can avoid such problems by choosing symbols that work across dialects. Note that in the below table, there is exactly one universally accepted codepoint for each symbol (these have been indicated by a single "Universal" cell stretching across the row), except for And where APL2 doesn't recognise the otherwise universal U+2227. However, APL2 does not have And extended to Least Common Multiple, so it is equivalent to Times (<syntaxhighlight lang=apl inline>×</syntaxhighlight>) which can therefore be used instead for truly portable code.


==Comparison of implementations==
==Comparison of implementations==
The following characters are included have been encountered in APL code displayed somewhere on the Internet or in a PDF file. Blindly copying them into an APL [[session]] can produce an error which might well confuse the user.
{| class=wikitable style=text-align:center
{| class=wikitable style=text-align:center
! APL name !! Glyph !! Codepoint !! Unicode name !! [[APL2]] !! [[Dyalog APL|Dyalog<br>APL]] !! [[GNU APL|GNU<br>APL]] !! [[NARS2000|NARS<br>2000]] !! [[ngn/apl|ngn/<br>apl]] !! [[dzaima/APL|dzaima/<br>APL]] !! Monadic || Dyadic  
! APL name !! Glyph !! Codepoint !! Unicode name !! [[APL2]] !! [[Dyalog APL|Dyalog<br>APL]] !! [[GNU APL|GNU<br>APL]] !! [[NARS2000|NARS<br>2000]] !! [[ngn/apl|ngn/<br>apl]] !! [[dzaima/APL|dzaima/<br>APL]] !! Monadic || Dyadic  
|-
|-
! rowspan=2 | Star
! rowspan=2 | Star
| <source lang=apl inline>*</source> || U+002A || Asterisk || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || rowspan=2 | [[Exponential]] || rowspan=2 | [[Power|Power]]
| <syntaxhighlight lang=apl inline>*</syntaxhighlight> || U+002A || Asterisk || colspan=6 {{Yes|Universal}} || rowspan=2 | [[Exponential]] || rowspan=2 | [[Power|Power]]
|-
|-
| <source lang=apl inline>⋆</source> || U+26AA ||Star operator || {{No}} || {{No}} || {{Yes}} || {{Yes}} || {{Yes}} || {{No}}
| <syntaxhighlight lang=apl inline>⋆</syntaxhighlight> || U+22C6 ||Star operator || {{No}} || {{No}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{No}}
|-
|-
! rowspan=2 | Minus
! rowspan=2 | Minus
| <source lang=apl inline>-</source> || U+002D || Hyphen-minus || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || rowspan=2 | [[Negate]] || rowspan=2 | [[Minus]]
| <syntaxhighlight lang=apl inline>-</syntaxhighlight> || U+002D || Hyphen-minus || colspan=6 {{Yes|Universal}} || rowspan=2 | [[Negate]] || rowspan=2 | [[Minus]]
|-
|-
| <source lang=apl inline>−</source> || U+2212 || Minus sign || {{No}} || {{No}} || {{Yes}} || {{Yes}} || {{Yes}} || {{No}}
| <syntaxhighlight lang=apl inline>−</syntaxhighlight> || U+2212 || Minus sign || {{No}} || {{No}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{No}}
|-
|-
! rowspan=2 | Logical And
! rowspan=2 | Logical And
| <source lang=apl inline>^</source> || U+005E || Circumflex accent  || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{No}} || rowspan=2 | || rowspan=2 | [[And]]
| <syntaxhighlight lang=apl inline>^</syntaxhighlight> || U+005E || Circumflex accent  || {{Maybe|Yes}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{No}} || rowspan=2 | || rowspan=2 | [[And]]
|-
|-
| <source lang=apl inline>∧</source> || U+22BD || Logical And || {{No}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}}
| <syntaxhighlight lang=apl inline>∧</syntaxhighlight> || U+2227 || Logical And || {{No|No<ref><syntaxhighlight lang=apl inline>×</syntaxhighlight> (U+00D7) is a universally supported substitute</ref>}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{Maybe|Yes}}
|-
|-
! rowspan=2 | Stile
! rowspan=2 | Stile
| <source lang=apl inline>|</source> || U+007C || Vertical line || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || rowspan=2 | [[Magnitude]] || rowspan=2 | [[Residue]]
| <syntaxhighlight lang=apl inline>|</syntaxhighlight> || U+007C || Vertical line || colspan=6 {{Yes|Universal}} || rowspan=2 | [[Magnitude]] || rowspan=2 | [[Residue]]
|-
|-
| <source lang=apl inline>∣</source> || U+2212 || Divides || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{No}}
| <syntaxhighlight lang=apl inline>∣</syntaxhighlight> || U+2223 || Divides || {{Maybe|Yes}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{No}}
|-
|-
! rowspan=2 | Tilde
! rowspan=2 | Tilde
| <source lang=apl inline>~</source> || U+007E || Tilde || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || rowspan=2 | [[Not]] || rowspan=2 | [[Without]]
| <syntaxhighlight lang=apl inline>~</syntaxhighlight> || U+007E || Tilde || colspan=6 {{Yes|Universal}} || rowspan=2 | [[Not]] || rowspan=2 | [[Without]]
|-
|-
| <source lang=apl inline>∼</source> || U+223C || Tilde operator || {{No}} || {{No}} || {{Yes}} || {{Yes}} || {{No}} || {{No}}
| <syntaxhighlight lang=apl inline>∼</syntaxhighlight> || U+223C || Tilde operator || {{No}} || {{No}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{No}} || {{No}}
|-
|-
! rowspan=2 | Alpha
! rowspan=2 | Alpha
| <source lang=apl inline>α</source> || U+03B1 || Greek small letter Alpha || rowspan=2 | || {{No}} || {{Yes}} || {{Yes}} || {{No}} || {{No}} || rowspan=2 colspan=2 | [[Left Argument]]
| <syntaxhighlight lang=apl inline>α</syntaxhighlight> || U+03B1 || Greek small letter Alpha || rowspan=2 | || {{No}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{No}} || {{No}} || rowspan=2 colspan=2 | [[dfn|Left Argument]]
|-
|-
| <source lang=apl inline>⍺</source> || U+237A || APL functional symbol Alpha || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}}
| <syntaxhighlight lang=apl inline>⍺</syntaxhighlight> || U+237A || APL functional symbol Alpha || colspan=5 {{Yes|Universal}}
|-
! rowspan=2 | Iota
| <syntaxhighlight lang=apl inline>ι</syntaxhighlight> || U+03B9 || Greek small letter Iota || {{No}} || {{No}} || {{Maybe|Yes}} || {{No}} || {{No}} || {{No}} || rowspan=2 colspan=2 | [[dfn|Left Argument]]
|-
| <syntaxhighlight lang=apl inline>⍳</syntaxhighlight> || U+2373 || APL functional symbol Iota || colspan=6 {{Yes|Universal}}
|-
! rowspan=2 | Rho
| <syntaxhighlight lang=apl inline>ρ</syntaxhighlight> || U+03C1 || Greek small letter Rho || {{No}} || {{No}} || {{Maybe|Yes}} || {{No}} || {{No}} || {{No}} || rowspan=2 colspan=2 | [[dfn|Left Argument]]
|-
| <syntaxhighlight lang=apl inline>⍴</syntaxhighlight> || U+2374 || APL functional symbol Rho || colspan=6 {{Yes|Universal}}
|-
|-
! rowspan=2 | Omega
! rowspan=2 | Omega
| <source lang=apl inline>ω</source> || U+03C9 || Greek small letter Omega || rowspan=2 | || {{No}} || {{Yes}} || {{Yes}} || {{No}} || {{No}} || rowspan=2 colspan=2 | [[Right Argument]]
| <syntaxhighlight lang=apl inline>ω</syntaxhighlight> || U+03C9 || Greek small letter Omega || rowspan=2 | || {{No}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{No}} || {{No}} || rowspan=2 colspan=2 | [[dfn|Right Argument]]
|-
| <syntaxhighlight lang=apl inline>⍵</syntaxhighlight> || U+2375 || APL functional symbol Omega || colspan=5 {{Yes|Universal}}
|-
|-
| <source lang=apl inline></source> || U+237A || APL functional symbol Omega || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}}
! rowspan=3 | Epsilon
| <syntaxhighlight lang=apl inline>ϵ</syntaxhighlight> || U+03F5 || Greek lunate Epsilon symbol || {{No}} || {{No}} || {{Maybe|Yes}} || {{No}} || {{No}} || {{No}} || rowspan=3 | [[Enlist]]/[[Type]] || rowspan=3 | [[Membership]]
|-
|-
! rowspan=2 | Epsilon
| <syntaxhighlight lang=apl inline>∈</syntaxhighlight><ref>Found by Hanspeter Moser in [https://www.gnu.org/software/apl/Bits_and_Pieces/toronto-toolkit.apl.html The Toronto Toolkit]</ref> || U+2208 || Element of || {{No}} || {{No}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{No}} || {{No}}
| <source lang=apl inline>∈</source><ref>Found by Hanspeter Moser in [https://www.gnu.org/software/apl/Bits_and_Pieces/toronto-toolkit.apl.html The Toronto Toolkit]</ref> || U+2208 || Element of || {{No}} || {{No}} || {{Yes}} || {{Yes}} || {{No}} || {{No}} || rowspan=2 | [[Enlist]]/[[Type]] || rowspan=2 | [[Membership]]
|-  
|-  
| <source lang=apl inline>∊</source> || U+220A || Small Element of || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}}
| <syntaxhighlight lang=apl inline>∊</syntaxhighlight> || U+220A || Small Element of || colspan=6 {{Yes|Universal}}
|-
|-
! rowspan=2 | Jot
! rowspan=2 | [[Jot]]
| <source lang=apl inline>∘</source> || U+2218 || Ring operator || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || rowspan=2 | [[Outer product]] || rowspan=2 | [[Beside]]/[[Beside]]
| <syntaxhighlight lang=apl inline>∘</syntaxhighlight> || U+2218 || Ring operator || colspan=6 {{Yes|Universal}} || rowspan=2 | [[Outer product]] || rowspan=2 | [[Beside]]/[[Bind]]
|-
|-
| <source lang=apl inline>◦</source> || U+25E6 || White bullet || {{No}} || {{No}} || {{Yes}} || {{Yes}} || {{No}} || {{No}}
| <syntaxhighlight lang=apl inline>◦</syntaxhighlight> || U+25E6 || White bullet || {{No}} || {{No}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{No}} || {{No}}
|-
|-
! rowspan=2 | Less than or<br>equal to
! rowspan=2 | Less than or<br>equal to
| <source lang=apl inline>≤</source> || U+2264 || Less-than or equal to || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || rowspan=2 | || rowspan=2 | [[Less than or equal to|Less than or<br>equal to]]
| <syntaxhighlight lang=apl inline>≤</syntaxhighlight> || U+2264 || Less-than or equal to || colspan=6 {{Yes|Universal}} || rowspan=2 | || rowspan=2 | [[Less than or equal to|Less than or<br>equal to]]
|-
|-
| <source lang=apl inline>⩽</source> || U+2A7D || Less than or slanted equal to  || {{No}} || {{No}} || {{Yes}} || {{Yes}} || {{No}} || {{No}}
| <syntaxhighlight lang=apl inline>⩽</syntaxhighlight> || U+2A7D || Less than or slanted equal to  || {{No}} || {{No}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{No}} || {{No}}
|-
|-
! rowspan=2 | Greater than or<br>equal to
! rowspan=2 | Greater than or<br>equal to
| <source lang=apl inline>≥</source> || U+2265 || Greater than or equal to || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || rowspan=2 | || rowspan=2 | [[Greater than or equal to|Greater than or<br>equal to]]
| <syntaxhighlight lang=apl inline>≥</syntaxhighlight> || U+2265 || Greater than or equal to || colspan=6 {{Yes|Universal}} || rowspan=2 | || rowspan=2 | [[Greater than or equal to|Greater than or<br>equal to]]
|-
|-
| <source lang=apl inline>⩾</source> || U+2A7E || Greater than or slanted equal to  || {{No}} || {{No}} || {{Yes}} || {{Yes}} || {{No}} || {{No}}
| <syntaxhighlight lang=apl inline>⩾</syntaxhighlight> || U+2A7E || Greater than or slanted equal to  || {{No}} || {{No}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{No}} || {{No}}
|-
|-
! rowspan=2 | Logical Nor
! rowspan=2 | Logical Nor
| <source lang=apl inline>⊽</source> || U+22BD || Nor || {{No}} || {{No}} || {{Yes}} || {{Yes}} || {{No}} || {{No}} || rowspan=2 | || rowspan=2 | [[Nor]]
| <syntaxhighlight lang=apl inline>⊽</syntaxhighlight> || U+22BD || Nor || {{No}} || {{No}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{No}} || {{No}} || rowspan=2 | || rowspan=2 | [[Nor]]
|-
|-
| <source lang=apl inline>⍱</source> || U+2371 || APL functional symbol down caret tilde  || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}}
| <syntaxhighlight lang=apl inline>⍱</syntaxhighlight> || U+2371 || APL functional symbol down caret tilde  || colspan=6 {{Yes|Universal}}
|-
|-
! rowspan=2 | Logical Nand
! rowspan=2 | Logical Nand
| <source lang=apl inline>⊼</source> || U+22BC || Nand || {{No}} || {{No}} || {{Yes}} || {{Yes}} || {{No}} || {{No}} || rowspan=2 | || rowspan=2 | [[Nand]]
| <syntaxhighlight lang=apl inline>⊼</syntaxhighlight> || U+22BC || Nand || {{No}} || {{No}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{No}} || {{No}} || rowspan=2 | || rowspan=2 | [[Nand]]
|-
|-
| <source lang=apl inline></source> || U+2372 || APL functional symbol up caret tilde  || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}}
| <syntaxhighlight lang=apl inline></syntaxhighlight> || U+2372 || APL functional symbol up caret tilde  || colspan=6 {{Yes|Universal}}
|-
|-
! rowspan=4 | Diamond
! rowspan=4 | Diamond
| <source lang=apl inline>⋄</source> || U+22C4 || Diamond operator || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || rowspan=4 colspan=2 | [[Statement Separator]]
| <syntaxhighlight lang=apl inline>⋄</syntaxhighlight> || U+22C4 || Diamond operator || colspan=6 {{Yes|Universal}} || rowspan=4 colspan=2 | [[Statement Separator]]
|-
|-
| <source lang=apl inline>◇</source> || U+25C7 || White Diamond    || {{No}} || {{No}} || {{No}} || {{Yes}} || {{No}} || {{No}}
| <syntaxhighlight lang=apl inline>◇</syntaxhighlight> || U+25C7 || White Diamond    || {{No}} || {{No}} || {{No}} || {{Maybe|Yes}} || {{No}} || {{No}}
|-
|-
| <source lang=apl inline>◊</source> || U+25CA || Lozenge          || {{No}} || {{No}} || {{Yes}} || {{Yes}} || {{No}} || {{No}}
| <syntaxhighlight lang=apl inline>◊</syntaxhighlight> || U+25CA || Lozenge          || {{No}} || {{No}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{No}} || {{No}}
|-
|-
| <source lang=apl inline>⬦</source> || U+2B26 || Diamond          || {{No}} || {{No}} || {{Yes}} || {{Yes}} || {{No}} || {{No}}
| <syntaxhighlight lang=apl inline>⬦</syntaxhighlight> || U+2B26 || Diamond          || {{No}} || {{No}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{No}} || {{No}}
|-
|-
! rowspan=2 | Quad
! rowspan=2 | Quad
| <source lang=apl inline>⎕</source> || U+2395 || APL functional symbol Quad  || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || rowspan=2 colspan=2 | [[Quad name]]
| <syntaxhighlight lang=apl inline>⎕</syntaxhighlight> || U+2395 || APL functional symbol Quad  || colspan=6 {{Yes|Universal}} || rowspan=2 colspan=2 | [[Quad name]]
|-
|-
| <source lang=apl inline>▯</source> || U+26AA || White vertical rectangle || {{Yes}} || {{No}} || {{Yes}} || {{Yes}} || {{No}} || {{No}}
| <syntaxhighlight lang=apl inline>▯</syntaxhighlight> || U+25AF || White vertical rectangle || {{Maybe|Yes}} || {{No}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{No}} || {{No}}
|-
|-
! rowspan=2 | Circle
! rowspan=2 | Circle
| <source lang=apl inline>○</source> || U+25CB || White circle || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || rowspan=2 | [[Pi Times]] || rowspan=2 | [[Circle function|Circular]]
| <syntaxhighlight lang=apl inline>○</syntaxhighlight> || U+25CB || White circle || colspan=6 {{Yes|Universal}} || rowspan=2 | [[Pi Times]] || rowspan=2 | [[Circle function|Circular]]
|-
|-
| <source lang=apl inline>⚪</source> || U+26AA || Medium white circle || {{No}} || {{No}} || {{Yes}} || {{Yes}} || {{No}} || {{No}}
| <syntaxhighlight lang=apl inline>⚪</syntaxhighlight> || U+26AA || Medium white circle || {{No}} || {{No}} || {{Maybe|Yes}} || {{Maybe|Yes}} || {{No}} || {{No}}
|}
|}
These characters are included here because they have been encountered them in APL code displayed somewhere on the Internet or in a PDF file. Thus blindly copying them into an APL [[session]] can produce an error which might well confuse the user.


== Functionality ==
== Functionality ==
The following statements can be used to test the functionality of the symbols:
The following statements can be used to test the functionality of the symbols:
<source lang=apl>
<syntaxhighlight lang=apl>
⍎⎕← '1',(⎕UCS 16⊥0  0  2 10),'1'  ⍝ Star
⍎⎕← '1',(⎕UCS 16⊥0  0  2 10),'1'  ⍝ Star
⍎⎕← '1',(⎕UCS 16⊥2  2 12  6),'1'  ⍝ Star
⍎⎕← '1',(⎕UCS 16⊥2  2 12  6),'1'  ⍝ Star
Line 139: Line 151:
⍎⎕← '1',(⎕UCS 16⊥2  6 10 10),'1'  ⍝ Circle
⍎⎕← '1',(⎕UCS 16⊥2  6 10 10),'1'  ⍝ Circle
⍎⎕← '1',(⎕UCS 16⊥2  3  7  2),'1'  ⍝ Nand
⍎⎕← '1',(⎕UCS 16⊥2  3  7  2),'1'  ⍝ Nand
</source>
</syntaxhighlight>
Note that the last four lines will not work on a system that doesn’t support [[dfns]].
Note that the last four lines will not work on a system that doesn’t support [[dfn]]s.


==Atomic Vector==
==Atomic Vector==
If the [[Atomic vector]] (<source lang=apl inline>⎕AV</source>) has no room in which to include these new characters, an implementation can translate them on entry to the corresponding symbol that is in <source lang=apl inline>⎕AV</source>. [[NARS2000]] even has a means of translating symbols on the way out via Copy (<kbd>Ctrl</kbd>+<kbd>C</kbd> in Windows) to various other APL systems that don't support the same set of principal characters NARS2000 uses for the functions in the above table.
If the [[Atomic vector]] (<syntaxhighlight lang=apl inline>⎕AV</syntaxhighlight>) has no room in which to include these new characters, an implementation can translate them on entry to the corresponding symbol that is in <syntaxhighlight lang=apl inline>⎕AV</syntaxhighlight>. [[NARS2000]] even has a means of translating symbols on the way out via Copy (<kbd>Ctrl</kbd>+<kbd>C</kbd> in Windows) to various other APL systems that don't support the same set of principal characters NARS2000 uses for the functions in the above table.


==Considerations==
==Considerations==
Line 150: Line 162:
== References ==
== References ==
<references/>
<references/>
{{APL glyphs}}[[Category:APL character set]]

Latest revision as of 13:03, 5 February 2024

The advent of Unicode solved many problems with dealing with APL characters, however there was still some wiggle room as to which Unicode codepoint were to be used in a Unicode implementation of APL, and different implementors made different choices. This article, which documents these differences, is adapted from an original paper by Bob Smith[1] that attempted to raise awareness of these issues because the differences impede transfer of information.

The relevant document for the APL character set is the APL Character Repertoire (ACR)[2]. For whatever reasons, that document never became a standard, but it does provide some guidance, and is better than each implementor making separate choices.

Introduction

There are a surprising number of similar APL characters in Unicode and in several cases some implementors went one way, others the other way. The following table lists the characters in question, along with the way APL2, Dyalog, GNU APL, NARS2000, ngn/apl, and dzaima/APL behave. APL2000 states that Generally the default codepoint scheme for the VisualAPL product follows the IBM APL2 workstation scheme. Please edit the table if you believe there are other characters that should be included in the table, or to add another dialect.

When there are differences among APL implementations, users can become confused. They type something into one APL system, copy it to another and are greeted by a SYNTAX ERROR or the like.

The whole basis for the confusion in a lengthy thread on comp.lang.apl entitled caret vs and[3] was that in some implementations the symbol for the logical And function was U+005E only, in some implementations it was U+2227 only, and in some both characters worked. The original poster encountered some APL text from the APL Wiki that had been produced by a system that supports U+005E and copied it into a system that used U+2227 only and failed on U+005E.

When systems differ in the set of acceptable characters for the same function, it serves only to confuse the end user to the detriment of the community. The cautious APL programmer can avoid such problems by choosing symbols that work across dialects. Note that in the below table, there is exactly one universally accepted codepoint for each symbol (these have been indicated by a single "Universal" cell stretching across the row), except for And where APL2 doesn't recognise the otherwise universal U+2227. However, APL2 does not have And extended to Least Common Multiple, so it is equivalent to Times (×) which can therefore be used instead for truly portable code.

Comparison of implementations

The following characters are included have been encountered in APL code displayed somewhere on the Internet or in a PDF file. Blindly copying them into an APL session can produce an error which might well confuse the user.

APL name Glyph Codepoint Unicode name APL2 Dyalog
APL
GNU
APL
NARS
2000
ngn/
apl
dzaima/
APL
Monadic Dyadic
Star * U+002A Asterisk Universal Exponential Power
U+22C6 Star operator No No Yes Yes Yes No
Minus - U+002D Hyphen-minus Universal Negate Minus
U+2212 Minus sign No No Yes Yes Yes No
Logical And ^ U+005E Circumflex accent Yes Yes Yes Yes Yes No And
U+2227 Logical And No[4] Yes Yes Yes Yes Yes
Stile | U+007C Vertical line Universal Magnitude Residue
U+2223 Divides Yes Yes Yes Yes Yes No
Tilde ~ U+007E Tilde Universal Not Without
U+223C Tilde operator No No Yes Yes No No
Alpha α U+03B1 Greek small letter Alpha No Yes Yes No No Left Argument
U+237A APL functional symbol Alpha Universal
Iota ι U+03B9 Greek small letter Iota No No Yes No No No Left Argument
U+2373 APL functional symbol Iota Universal
Rho ρ U+03C1 Greek small letter Rho No No Yes No No No Left Argument
U+2374 APL functional symbol Rho Universal
Omega ω U+03C9 Greek small letter Omega No Yes Yes No No Right Argument
U+2375 APL functional symbol Omega Universal
Epsilon ϵ U+03F5 Greek lunate Epsilon symbol No No Yes No No No Enlist/Type Membership
[5] U+2208 Element of No No Yes Yes No No
U+220A Small Element of Universal
Jot U+2218 Ring operator Universal Outer product Beside/Bind
U+25E6 White bullet No No Yes Yes No No
Less than or
equal to
U+2264 Less-than or equal to Universal Less than or
equal to
U+2A7D Less than or slanted equal to No No Yes Yes No No
Greater than or
equal to
U+2265 Greater than or equal to Universal Greater than or
equal to
U+2A7E Greater than or slanted equal to No No Yes Yes No No
Logical Nor U+22BD Nor No No Yes Yes No No Nor
U+2371 APL functional symbol down caret tilde Universal
Logical Nand U+22BC Nand No No Yes Yes No No Nand
U+2372 APL functional symbol up caret tilde Universal
Diamond U+22C4 Diamond operator Universal Statement Separator
U+25C7 White Diamond No No No Yes No No
U+25CA Lozenge No No Yes Yes No No
U+2B26 Diamond No No Yes Yes No No
Quad U+2395 APL functional symbol Quad Universal Quad name
U+25AF White vertical rectangle Yes No Yes Yes No No
Circle U+25CB White circle Universal Pi Times Circular
U+26AA Medium white circle No No Yes Yes No No

Functionality

The following statements can be used to test the functionality of the symbols:

⍎⎕← '1',(⎕UCS 16⊥0  0  2 10),'1'   ⍝ Star
⍎⎕← '1',(⎕UCS 16⊥2  2 12  6),'1'   ⍝ Star
⍎⎕← '1',(⎕UCS 16⊥0  0  2 13),'1'   ⍝ Minus
⍎⎕← '1',(⎕UCS 16⊥2  2  1  2),'1'   ⍝ Minus
⍎⎕← '1',(⎕UCS 16⊥0  0  5 14),'1'   ⍝ And
⍎⎕← '1',(⎕UCS 16⊥2  2  2  7),'1'   ⍝ And
⍎⎕← '1',(⎕UCS 16⊥0  0  7 12),'1'   ⍝ Modulus
⍎⎕← '1',(⎕UCS 16⊥2  2  2  3),'1'   ⍝ Modulus
⍎⎕←     (⎕UCS 16⊥0  0  7 14),'1'   ⍝ Tilde
⍎⎕←     (⎕UCS 16⊥2  2  3 12),'1'   ⍝ Tilde
⍎⎕←'1{',(⎕UCS 16⊥0  3 11  1),'}1'  ⍝ Alpha
⍎⎕←'1{',(⎕UCS 16⊥2  3  7 10),'}1'  ⍝ Alpha
⍎⎕← '{',(⎕UCS 16⊥0  3 12  9),'}1'  ⍝ Omega
⍎⎕← '{',(⎕UCS 16⊥2  3  7  5),'}1'  ⍝ Omega
⍎⎕← '1',(⎕UCS 16⊥2  2  0  8),'1'   ⍝ Epsilon
⍎⎕← '1',(⎕UCS 16⊥2  2  0 10),'1'   ⍝ Epsilon
⍎⎕← '1',(⎕UCS 16⊥2  2  1  8),'.=1' ⍝ Jot
⍎⎕← '1',(⎕UCS 16⊥2  5 14  6),'.=1' ⍝ Jot
⍎⎕← '1',(⎕UCS 16⊥2  2  6  4),'1'   ⍝ Less than or equal to
⍎⎕← '1',(⎕UCS 16⊥2 10  7 13),'1'   ⍝ Less than or equal to
⍎⎕← '1',(⎕UCS 16⊥2  2  6  5),'1'   ⍝ Greater than or equal to
⍎⎕← '1',(⎕UCS 16⊥2 10  7 14),'1'   ⍝ Greater than or equal to
⍎⎕← '1',(⎕UCS 16⊥2  2 11 13),'1'   ⍝ Nor
⍎⎕← '1',(⎕UCS 16⊥2  3  7  1),'1'   ⍝ Nor
⍎⎕← '1',(⎕UCS 16⊥2  2 11 12),'1'   ⍝ Nand
⍎⎕← '1',(⎕UCS 16⊥2  2 12  4),'1'   ⍝ Diamond
⍎⎕← '1',(⎕UCS 16⊥2  5 12  7),'1'   ⍝ Diamond
⍎⎕← '1',(⎕UCS 16⊥2  5 12 10),'1'   ⍝ Diamond
⍎⎕← '1',(⎕UCS 16⊥2 11  2  6),'1'   ⍝ Diamond
⍎⎕←     (⎕UCS 16⊥2  3  9  5),'←1'  ⍝ Quad
⍎⎕←     (⎕UCS 16⊥2  5 10 15),'←1'  ⍝ Quad
⍎⎕← '1',(⎕UCS 16⊥2  5 12 11),'1'   ⍝ Circle
⍎⎕← '1',(⎕UCS 16⊥2  6 10 10),'1'   ⍝ Circle
⍎⎕← '1',(⎕UCS 16⊥2  3  7  2),'1'   ⍝ Nand

Note that the last four lines will not work on a system that doesn’t support dfns.

Atomic Vector

If the Atomic vector (⎕AV) has no room in which to include these new characters, an implementation can translate them on entry to the corresponding symbol that is in ⎕AV. NARS2000 even has a means of translating symbols on the way out via Copy (Ctrl+C in Windows) to various other APL systems that don't support the same set of principal characters NARS2000 uses for the functions in the above table.

Considerations

Unicode was a great start to enabling APL characters to be used, however in order for there to be interoperability, implementors have to agree upon which characters are functional. It doesn't matter if one's system can change the mapping of glyphs to codepoints as the vast majority of users won't change from the default behavior. Implementors therefore have to decide if it is worthwhile to support the above codepoints.

References

  1. Smith, Bob. APL Characters and Their Aliases. 14 Dec 2013–25 Dec 2019. Sudley Place Software.
  2. ISO-IEC/JTC1/SC22/WG3. N3067: APL Character Repertoire. 28 Dec 1999.
  3. comp.lang.apl. caret vs and. 28 Oct 2013–9 Dec 2013
  4. × (U+00D7) is a universally supported substitute
  5. Found by Hanspeter Moser in The Toronto Toolkit
APL glyphs [edit]
Information GlyphTyping glyphs (on Linux) ∙ UnicodeFontsMnemonicsOverstrikesMigration level
Individual glyphs Jot () ∙ Right Shoe () ∙ Up Arrow () ∙ Zilde () ∙ High minus (¯) ∙ Dot (.) ∙ Del ()