Difference between revisions of "System Variable FPC"

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[[Category:System functions]] [[Category:Math functions]]

Revision as of 10:11, 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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