System Variable FPC: Difference between revisions

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=Floating Point Control=
<h1><aplxx>⎕FPC</aplxx> - Floating Point Control</h1>
{{BoxStart|<apll>Z←⎕FPC</apll>
|returns the current value of the Floating Point Control precision.}}
{{BoxEnd|<apll>Z</apll> is an integer scalar that represents the current value of the number of bits of precision used for [[Rational and VFP Numbers|Multiple-Precision Floating Point numbers]].}}
<br />


<table border="1" cellpadding="5" cellspacing="0" rules="none" summary="">
{| border="1" cellpadding="5" cellspacing="0" rules="none" summary=""
<tr>
|-
  <td>
||<apll>⎕FPC←R</apll>
    <table border="0" cellpadding="5" cellspacing="0" summary="">
||sets the value of the Floating Point Control precision to <apll>R</apll>.
    <tr>
|-
      <td valign="top"><apll>Z←⎕FPC</apll></td>
||<apll>⎕FPC←⍬</apll>
      <td></td>
||sets the value of the Floating Point Control precision to its system default state.
      <td></td>
|}
      <td>returns the current value of the Floating Point Control precision.</td>
    </tr>
    </table>
  </td>
</tr>
<tr>
  <td><apll>Z</apll> is an integer scalar that represents the current value of the number of bits of precision used for [[Rational and VFP Numbers|VFP numbers]].</td>
</tr>
</table>
<br />
<br />


<table border="1" cellpadding="5" cellspacing="0" rules="none" summary="">
<p>
<tr>
The approximate number of digits of precision for a given value of <apll>⎕FPC</apll> is about <apll>10⍟2*⎕FPC</apll>. The value of <apll>⎕FPC</apll> for a given required precision is about <apll>⌈2⍟10*digits</apll>.
  <td>
</p>
    <table border="0" cellpadding="5" cellspacing="0" summary="">
    <tr>
      <td valign="top"><apll>⎕FPC←R</apll></td>
      <td></td>
      <td></td>
      <td>sets the value of the Floating Point Control precision to <apll>R</apll>.</td>
    </tr>
    <tr>
      <td valign="top"><apll>⎕FPC←⍬</apll></td>
      <td></td>
      <td></td>
      <td>sets the value of the Floating Point Control precision to its system default state.</td>
    </tr>
    </table>
  </td>
</tr>
</table>
<br />


<p>The minimum value for <apll>⎕FPC</apll> is <apll>53</apll>; the maximum value is the largest positive 32-bit integer <apll>2147483647</apll>.</p>
<p>The minimum value for <apll>⎕FPC</apll> is <apll>1</apll>; the maximum value is the integer <apll>1073741695 ←→ ¯129+2*30 ←→ 16<_b/>3FFFFF7F</apll>.</p>


<p>The system default value is <apll>128</apll>.</p>
<p>The system default value is <apll>128</apll>.</p>




<p>For example, (note: these numbers are normally one long string of digits; they are broken here, with the break shown by '''{continued)''' for your convenience in reading)</p>
<p>For example:</p>


<apll>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;⎕PP←200<br />
<apll><pre>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;⎕FPC←64 &nbsp;⋄ *1x<br />
&ensp;&ensp;     ⎕PP←240
2.71828182845904523543<br />
&ensp;&ensp;     ⎕FPC←64  ⋄ *1<_x/>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;⎕FPC←128 ⋄ *1x<br />
&ensp;&ensp;2.7182818284590452354
2.718281828459045235360287471352662497759<br />
&ensp;&ensp;     ⎕FPC←128  ⋄ *1<_x/>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;⎕FPC←256 ⋄ *1x<br />
&ensp;&ensp;2.71828182845904523536028747135266249776
2.71828182845904523536028747135266249775724709369995957 (Continued)<br/>4966967627724076630353555<br />
&ensp;&ensp;     ⎕FPC←256  ⋄ *1<_x/>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;⎕FPC←512 ⋄ *1x<br />
&ensp;&ensp;2.71828182845904523536028747135266249775724709369995957496696762
2.71828182845904523536028747135266249775724709369995957 (Continued)<br/>
<_lc/>     772407663035355
49669676277240766303535475945713821785251664274274663919 (Continued)<br/>
&ensp;&ensp;     ⎕FPC←512  ⋄ *1<_x/>
3200305992181741359662904357290033429526059559</apll>
&ensp;&ensp;2.71828182845904523536028747135266249775724709369995957496696762
<_lc/>     7724076630353547594571382178525166427427466391932003059921
<_lc/>     8174135966290435729003342952605956
&ensp;&ensp;     ⎕FPC←1024 ⋄ *1<_x/>
&ensp;&ensp;2.71828182845904523536028747135266249775724709369995957496696762
<_lc/>     7724076630353547594571382178525166427427466391932003059921
<_lc/>     8174135966290435729003342952605956307381323286279434907632
<_lc/>     3382988075319525101901157383418793070215408914993488416750
<_lc/>      924</pre></apll>


<p>Whereas, according to Wolfram Alpha, the exact value to 230 digits is</p>
<p>Whereas, according to Wolfram Alpha, the exact value to 230 digits is</p>


<apll>2.71828182845904523536028747135266249775724709369995957496 (Continued)<br/>
<apll><pre>&ensp;&ensp;2.71828182845904523536028747135266249775724709369995957496696762
6967627724076630353547594571382178525166427427466391932003059921 (Continued)<br/>
<_lc/>     7724076630353547594571382178525166427427466391932003059921
8174135966290435729003342952605956307381323286279434907632338298 (Continued)<br/>
<_lc/>     8174135966290435729003342952605956307381323286279434907632
8075319525101901157383418793070215408914993488...</apll><br />
<_lc/>     3382988075319525101901157383418793070215408914993488...</pre></apll>
 
'''See Also: [[System_Variable_CT|Comparison Tolerance ⎕CT]]'''
 


{{SFM|FPC}}
{{System Variables}}
{{System Variables}}
{{Article footer|0|NO}}
[[Category:System functions|FPC]] [[Category:Math functions|FPC]]

Latest revision as of 23:03, 13 October 2019

⎕FPC - Floating Point Control

Z←⎕FPC returns the current value of the Floating Point Control precision.
Z is an integer scalar that represents the current value of the number of bits of precision used for Multiple-Precision Floating Point numbers.


⎕FPC←R sets the value of the Floating Point Control precision to R.
⎕FPC←⍬ sets the value of the Floating Point Control precision to its system default state.


The approximate number of digits of precision for a given value of ⎕FPC is about 10⍟2*⎕FPC. The value of ⎕FPC for a given required precision is about ⌈2⍟10*digits.

The minimum value for ⎕FPC is 1; the maximum value is the integer 1073741695 ←→ ¯129+2*30 ←→ 16b3FFFFF7F.

The system default value is 128.


For example:

        ⎕PP←240 
        ⎕FPC←64   ⋄ *1x
  2.7182818284590452354 
        ⎕FPC←128  ⋄ *1x
  2.71828182845904523536028747135266249776 
        ⎕FPC←256  ⋄ *1x
  2.71828182845904523536028747135266249775724709369995957496696762 
➥      772407663035355
        ⎕FPC←512  ⋄ *1x
  2.71828182845904523536028747135266249775724709369995957496696762
➥      7724076630353547594571382178525166427427466391932003059921
➥      8174135966290435729003342952605956 
        ⎕FPC←1024 ⋄ *1x
  2.71828182845904523536028747135266249775724709369995957496696762
➥      7724076630353547594571382178525166427427466391932003059921
➥      8174135966290435729003342952605956307381323286279434907632
➥      3382988075319525101901157383418793070215408914993488416750
➥      924

Whereas, according to Wolfram Alpha, the exact value to 230 digits is

  2.71828182845904523536028747135266249775724709369995957496696762
➥      7724076630353547594571382178525166427427466391932003059921
➥      8174135966290435729003342952605956307381323286279434907632
➥      3382988075319525101901157383418793070215408914993488...

See Also: Comparison Tolerance ⎕CT


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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