System Function EA: Difference between revisions

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* assign/set a value
* assign/set a value


'''[[System_Variable_ELX|See ALSO: ⎕ELX]]'''<br>
An APL Interpreter error (such as 'Domain Error') which '''triggers the Left argument of ⎕EA''' will also send a Diagnostic Error Message to
⎕DM, for debugging purposes, if needed by User. ⎕EA like ⎕ELX is useful in situations when a known error frequently occurs and the User Function knows how to work around or deal with it appropriately by say '''assigning a different value''' than the right argument - see the above examples.<br><br>
See ALSO:'''[[System_Variable_ELX| ⎕ELX]] and [[System_Variable_DM|⎕DM]]'''<br><br>


{{System Variables}}
{{System Variables}}
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Latest revision as of 18:20, 11 February 2015

⎕EA - Execute Alternate

⎕EA Execute Alternate string expression
Z ← L ⎕EA R   where arguments L and R are string expressions.'

Dyadic Function

Z←L ⎕EA R "L" is executed if "R" fails, and the result may be assigned to a variable, like Z.
Both L and R should be string expressions. The result can be numeric, string or otherwise.


Quad Execute Alternate ⎕EA sample dyadic calls: 

      Z←'5÷1' ⎕EA 'a÷1'   ⍝ Right argument FAILS(a÷1, because variable "a" does NOT exist), so LEFT argument (5÷1) is assigned to Z.
      Z
5
      Z←'5÷1' ⎕EA '6÷0.5' ⍝ RIGHT argument SUCCEEDS(6÷0.5), so Z becomes 6 divided by 0.5 or 12.
      Z
12

The Execute Alternate system function normally takes a string as left and right arguments. The left string(L) is executed when the interpreter encounters an error executing the right argument(R). In particular the left argument string may normally:

  • call a function
  • jump to a particular label
  • perform ANY allowed APL operation (e.g. addition, multiplication, division, subtraction, floor, ceiling, logic test, etc...)
  • assign/set a value

An APL Interpreter error (such as 'Domain Error') which triggers the Left argument of ⎕EA will also send a Diagnostic Error Message to ⎕DM, for debugging purposes, if needed by User. ⎕EA like ⎕ELX is useful in situations when a known error frequently occurs and the User Function knows how to work around or deal with it appropriately by say assigning a different value than the right argument - see the above examples.

See ALSO: ⎕ELX and ⎕DM

System Variables (A value may be assigned to these except for ⎕DM)
⎕ALX ⎕CT ⎕DM ⎕DT ⎕ELX ⎕FC ⎕FEATURE ⎕FPC ⎕IC ⎕IO
⎕LR ⎕LX ⎕PP ⎕PR ⎕PW ⎕RL ⎕SA ⎕WSID
Niladic System Functions (a value cannot be assigned to these)
⎕A ⎕AV ⎕EM ⎕ET ⎕LC ⎕NNAMES ⎕NNUMS ⎕SI ⎕SYSID ⎕SYSVER
⎕T ⎕TC ⎕TCBEL ⎕TCBS ⎕TCESC ⎕TCFF ⎕TCHT ⎕TCLF ⎕TCNL ⎕TCNUL
⎕TS ⎕WA
Monadic or dyadic system functions (a value cannot be assigned to these)
⎕AT ⎕CR ⎕DC ⎕DFT ⎕DL ⎕DR ⎕EA ⎕EC ⎕ERROR ⎕ES
⎕EX ⎕FMT ⎕FX ⎕MF ⎕NAPPEND ⎕NC ⎕NCREATE ⎕NERASE ⎕NINFO ⎕NL
⎕NLOCK ⎕NREAD ⎕NRENAME ⎕NREPLACE ⎕NRESIZE ⎕NSIZE ⎕NTIE ⎕NUNTIE ⎕STOP ⎕TF
⎕TRACE ⎕UCS ⎕VR
Note that quad functions and variables (except for the ⎕A family of functions) are case insensitive


See Also
System Commands System Variables and Functions Operators


Keyboard
Alt+Shift ⍪ ≡ ≢ ⍒ ⍋ ⌽ ⍉ ⊖ ⍟ ⍱ ⍲ ⍠ ⌹
Alt ⋄ ¨ ¯ < ≤ ∅ ≥ > ≠ ∨ ∧ × ÷
Shift ~ ! @ # $ % ^ & * ( ) _ +
Key ` 1 2 3 4 5 6 7 8 9 0 - =
Alt+Shift ⍷ √ ⍨ ⍸ ⍥ ⍣ ⍞ ⍬ ⊣
Alt ? ⍵ ∊ ⍴ § ↑ ↓ ⍳ ○ π ← → ⊢
Shift Q W E R T Y U I O P { } |
Key q w e r t y u i o p [ ] \
Alt+Shift ∫ ∂ ⌻ ⍢ ⍙ ⍤ ⍫ ⌷
Alt ⍺ ⌈ ⌊ ∞ ∇ ∆ ∘ ‼ ⎕ ⍎ ⍕
Shift A S D F G H J K L : "
Key a s d f g h j k l ; '
Alt+Shift ⊆ ⊇ χ ⍡ ⍭ ⊙
Alt ⊂ ⊃ ∩ ∪ ⊥ ⊤ ⍦ ⍝ ⍀ ⌿
Shift Z X C V B N M < > ?
Key z x c v b n m , . /
NARS 2000 Lang
Tool
Bar 		← → + - × ÷ * ⍟ ⌹ ○ ! ? √ | ⌈ ⌊ ⊥ ⊤ ⊣ ⊢
≡ ≢ < ≤ = ≥ > ≠ ∨ ∧ ⍱ ⍲ ↑ ↓ ⊂ ⊃ ⌷ ⍋ ⍒
⍳ ∊ ⍸ ⍷ ∪ ∩ ⊆ ⊇ ~ § π .. , ⍪ ⍴ ⌽ ⊖ ⍉
/ \ ⌿ ⍀ ⊙ ¨ ⍨ ⍤ ⍣ ⍡ ⍥ ⍦ . ∘ ⍠ ‼ ⌻ ∂ ∫ ⍞ ⎕ ⍎ ⍕
⋄ ⍝ ∇ ∆ ⍙ _ ⍺ ⍵ ¯ ⍬ ∞ ∅
Second Row i j k i j k l g p r v x

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