System Variable IC: Difference between revisions

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<tr>
<tr>
   <td align="center">3</td>
   <td align="center">3</td>
   <td align="center"><apll>0×∞</apll> and <apll>∞×0</apll></td>
   <td align="center"><apll>0×∞</apll> or <apll>∞×0</apll></td>
   <td align="center"><apll>DOMAIN ERROR</apll></td>
   <td align="center"><apll>DOMAIN ERROR</apll></td>
</tr>
</tr>
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<tr>
<tr>
   <td align="center">4</td>
   <td align="center">4</td>
   <td align="center"><apll>0ׯ∞</apll> and <apll>¯∞×0</apll></td>
   <td align="center"><apll>0ׯ∞</apll> or <apll>¯∞×0</apll></td>
   <td align="center"><apll>DOMAIN ERROR</apll></td>
   <td align="center"><apll>DOMAIN ERROR</apll></td>
</tr>
</tr>
Line 105: Line 105:
<tr>
<tr>
   <td align="center">8</td>
   <td align="center">8</td>
   <td align="center"><apll>∞-∞</apll> (and related)</td>
   <td align="center"><apll>∞-∞</apll> (same sign)</td>
   <td align="center"><apll>DOMAIN ERROR</apll></td>
   <td align="center"><apll>DOMAIN ERROR</apll></td>
</tr>
</tr>
Line 111: Line 111:
<tr>
<tr>
   <td align="center">9</td>
   <td align="center">9</td>
   <td align="center"><apll>L|∞</apll> (either sign infinity)</td>
   <td align="center"><apll>L|±∞</apll></td>
   <td align="center"><apll>DOMAIN ERROR</apll></td>
   <td align="center"><apll>DOMAIN ERROR</apll></td>
</tr>
</tr>
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   <td align="center"><apll>1⍟1</apll></td>
   <td align="center"><apll>1⍟1</apll></td>
   <td align="center"><apll>1</apll></td>
   <td align="center"><apll>1</apll></td>
</tr>
<tr>
  <td align="center">16</td>
  <td align="center"><apll>0*∞</apll></td>
  <td align="center"><apll>0</apll></td>
</tr>
<tr>
  <td align="center">17</td>
  <td align="center"><apll>0*¯∞</apll></td>
  <td align="center"><apll>∞</apll></td>
</tr>
<tr>
  <td align="center">18</td>
  <td align="center"><apll>±∞*0</apll></td>
  <td align="center"><apll>DOMAIN ERROR</apll></td>
</tr>
<tr>
  <td align="center">19</td>
  <td align="center"><apll>0∨±∞</apll> or <apll>±∞∨0</apll></td>
  <td align="center"><apll>DOMAIN ERROR</apll></td>
</tr>
<tr>
  <td align="center">20</td>
  <td align="center"><apll>0∧±∞</apll> or <apll>±∞∧0</apll></td>
  <td align="center"><apll>DOMAIN ERROR</apll></td>
</tr>
</tr>


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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;⎕IO←0<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;⎕IO←0<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;⎕IC<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;⎕IC<br />
3 4 2 2 2 1 2 2 2 2 1 2 2 2 2 1<br />
3 4 2 2 2 1 2 2 2 2 1 2 1 2 2 1 0 3 2 2 2<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0÷0<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;0÷0<br />
1<br />
1<br />
Line 208: Line 238:
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;⎕IC←⍬<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;⎕IC←⍬<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;⎕IC<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;⎕IC<br />
3 4 2 2 2 1 2 2 2 2 1 2 2 2 2 1<br />
3 4 2 2 2 1 2 2 2 2 1 2 1 2 2 1 0 3 2 2 2<br />
</apll>
</apll>
To set all indeterminate results to <apll>DOMAIN ERROR</apll>, use <apll>⎕IC[]←2</apll>.


==Incomplete List of Indeterminates==
==Incomplete List of Indeterminates==


<p>That there may be other indeterminates not covered by this feature.  Please let us know if you think there are other cases that should be included.</p>
<p>That there may be other indeterminates not covered by this feature.  Please let us know if you think there are other cases that should be included.</p>

Revision as of 19:55, 18 May 2011

Indeterminate Control

Z←⎕IC returns the current value of the Indeterminate Control Vector.
Z is an integer vector whose elements each control a separate aspect of how indeterminates are handled by the system.


⎕IC←R sets all of the values of the Indeterminate Control Vector to R.
⎕IC←⍬ sets all of the values of the Indeterminate Control Vector to their system default state.
⎕IC[L]←R sets the value(s) of the Indeterminate Control Vector indexed by L to R.


This experimental feature attempts to collect together in one place control of various infinite and indeterminate calculations such as ÷0, 0÷0, and friends. The values of this multi-element vector each control a different calculation. In particular,

⎕IC Index
(origin-0)		 Indeterminate
Calculation		 Default
Result
0 ÷0 ∞
1 ⍟0 ¯∞
2 !N for integer N<0 DOMAIN ERROR
3 0×∞ or ∞×0 DOMAIN ERROR
4 0ׯ∞ or ¯∞×0 DOMAIN ERROR
5 0÷0 1
6 ∞÷∞ (same sign) DOMAIN ERROR
7 ∞÷∞ (different sign) DOMAIN ERROR
8 ∞-∞ (same sign) DOMAIN ERROR
9 L|±∞ DOMAIN ERROR
10 0*0 1
11 L*∞ for any L≤¯1 DOMAIN ERROR
12 0⍟0 DOMAIN ERROR
13 0⍟1 DOMAIN ERROR
14 1⍟0 DOMAIN ERROR
15 1⍟1 1
16 0*∞ 0
17 0*¯∞ ∞
18 ±∞*0 DOMAIN ERROR
19 0∨±∞ or ±∞∨0 DOMAIN ERROR
20 0∧±∞ or ±∞∧0 DOMAIN ERROR

The values in each element of ⎕IC control the result of the calculation as follows:

⎕IC Value Result
¯1 ¯1
0 0
1 1
2 DOMAIN ERROR
3 ∞
4 ¯∞

For example,

      ⎕IO←0
      ⎕IC
3 4 2 2 2 1 2 2 2 2 1 2 1 2 2 1 0 3 2 2 2
      0÷0
1
      ⎕IC[5]←2
      0÷0
DOMAIN ERROR
      0÷0
       ∧
      ⎕IC←⍬
      ⎕IC
3 4 2 2 2 1 2 2 2 2 1 2 1 2 2 1 0 3 2 2 2

To set all indeterminate results to DOMAIN ERROR, use ⎕IC[]←2.

Incomplete List of Indeterminates

That there may be other indeterminates not covered by this feature. Please let us know if you think there are other cases that should be included.

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