System Variable IO: Difference between revisions

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<h1><apl>{quad}IO</apl> - Index Origin</h1>
<h1><aplxx>⎕IO</aplxx> - Index Origin</h1>
{{BoxStart|<apll>Z←⎕IO</apll>
{{BoxStart|<apll>Z←⎕IO</apll>
| returns the current value of the Index Origin. }}
| returns the current value of the Index Origin. }}
{{BoxEnd|<apll>Z</apll> is an integer vector containing the current value of ⎕IO. This is the lowest value of an array subscript, and is either 1 or 0.}}<br/>
{{BoxEnd|<apll>Z</apll> is an integer scalar containing the current value of <apll>⎕IO</apll>. This is the lowest value of an array subscript, and is either <apll>1</apll> or <apll>0</apll>.}}<br/>


{| border="1" cellpadding="5" cellspacing="0" rules="none" summary=""
{| border="1" cellpadding="5" cellspacing="0" rules="none" summary=""
|| <apll>⎕IO←0</apll> || set the lowest subscript of an array to 0.
|| <apll>⎕IO←0</apll> || sets the lowest subscript of an array to <apll>0</apll>
|-
|-
| valign="top" |<apll>⎕IO←1</apll> || sets the lowest subscript for arrays to 1
| valign="top" |<apll>⎕IO←1</apll> || sets the lowest subscript of an array to <apll>1</apll>
|-
|-
|}
|}
<br />
<br />
⎕IO determines the lowest subscript for arrays. The default is 1, but can be changed to 0. If an attempt is made to set ⎕IO to a value higher than 1, it is set to 1. If an attempt is made to set ⎕IO to a value loweer than 0, it is set to 0. Setting ⎕IO to anything other than a number causes a DOMAIN ERROR.  
<apll>⎕IO</apll> determines the lowest subscript for arrays. The default is <apll>1</apll>, but can be changed to <apll>0</apll>. If an attempt is made to set <apll>⎕IO</apll> to a value higher than <apll>1</apll>, it is set to <apll>1</apll>. If an attempt is made to set <apll>⎕IO</apll> to a value lower than <apll>0</apll>, it is set to <apll>0</apll>. Setting <apll>⎕IO</apll> to anything other than a number causes a <apll>DOMAIN ERROR</apll>.  


<pre>
<apll><pre>
    ⎕IO   ⍝ default ⎕IO (quad IO) is 1 in a clear workspace
      ⎕IO   ⍝ default ⎕IO is 1 in a clear workspace
1
1
       ⍳5    ⍝ iota 5
       ⍳5    ⍝ iota 5
1 2 3 4 5  
1 2 3 4 5  


       ⎕IO←0     ⍝ Set index origin ⎕IO to 0 (zero)
       ⎕IO←0 ⍝ Set index origin ⎕IO to 0  


       ⍳5   ⍝ iota 5 again but compare the results just below to just above
       ⍳5   ⍝ iota 5 again but compare the results just below to just above
0 1 2 3 4
0 1 2 3 4
</pre>
</pre></apll>


{{System Variables}}
{{System Variables}}
{{Article footer}}
{{Article footer}}

Latest revision as of 12:50, 16 April 2018

⎕IO - Index Origin

Z←⎕IO returns the current value of the Index Origin.
Z is an integer scalar containing the current value of ⎕IO. This is the lowest value of an array subscript, and is either 1 or 0.


⎕IO←0 sets the lowest subscript of an array to 0
⎕IO←1 sets the lowest subscript of an array to 1


⎕IO determines the lowest subscript for arrays. The default is 1, but can be changed to 0. If an attempt is made to set ⎕IO to a value higher than 1, it is set to 1. If an attempt is made to set ⎕IO to a value lower than 0, it is set to 0. Setting ⎕IO to anything other than a number causes a DOMAIN ERROR. 

      ⎕IO   ⍝ default ⎕IO is 1 in a clear workspace
1
      ⍳5    ⍝ iota 5
1 2 3 4 5 

      ⎕IO←0 ⍝ Set index origin ⎕IO to 0 

      ⍳5    ⍝ iota 5 again but compare the results just below to just above
0 1 2 3 4
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


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