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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 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.


  1. Dyalog Ltd. Programming Reference Guide. APL Line Editor.
  2. Dyalog Ltd. Programming Reference Guide. Recursion.
  3. Dyalog Ltd. Programming Reference Guide. Methods.
  4. MicroAPL. APLX Help. User-defined Functions.
  5. Dyalog Ltd. Language Reference Guide. Lock Definition.
APL glyphs [edit]
Information GlyphTyping glyphs (on Linux) ∙ UnicodeFontsMnemonicsOverstrikesMigration level
Individual glyphs Jot () ∙ Right Shoe () ∙ Up Arrow () ∙ Zilde () ∙ High minus (¯) ∙ Dot (.) ∙ Del ()