expressions

[Ofloo]

how can i do powers without having expr pow(x,y) using scientific notifications cause i am working with huge figurs and it must be accurant

Code: Select all

proc pow {e arg} {
  for {set i 0} {$i <= $e} {incr i} {
    if {[info exists expr]} {
      set expr [expr $expr*$arg]
    } else {
      set expr 1
    }
  }
  return $expr
}

i got this but it isn't able to handle big numbers ..

[spock]

i would consider using bc instead of tcl for this. large numbers should be no problem.

$ echo 5^100 | bc
7888609052210118054117285652827862296732064351090230047702789306640625

[strikelight]

From the expr manpage entry:

The global variable tcl_precision determines the number of significant digits that are retained when floating values are converted to strings (except that trailing zeroes are omitted). If tcl_precision is unset then 6 digits of precision are used. To retain all of the significant bits of an IEEE floating-point number set tcl_precision to 17; if a value is converted to string with 17 digits of precision and then converted back to binary for some later calculation, the resulting binary value is guaranteed to be identical to the original one.

Also see:
http://wiki.tcl.tk/683

^- So from the routines there, you can construct your pow function as such:

Code: Select all

proc pow {num pow} { 
  set b [tolist 1] 
  set num [tolist $num]
  for {set i 0} {$i < $pow} {incr i} { 
    set b [multa $b $num] 
  } 
  fromlist $b 
}

% pow 2 4
16
% pow 14 20
83668255425284801560576

[Ofloo]

hmm is it a lib i should load or .. cause those cmds do not exist (tolist, ..) or should i copy the procs from that page ..

hmm what i mean is is that a lib ..?

[strikelight]

Did you actually read that page? You would have answered your own question and saved us both time...

<snip>
^- So from the routines there, you can construct your pow function as such
<snip>

[Ofloo]

yes most of it anyway but i am not that good with technical english words ..

[Ofloo]

oh ok sorry

[strikelight]

Even still, assumedly, you know Tcl, and can see the procs there matching the commands that you know don't exist in stock Tcl language...

[Ofloo]

yes ur right but i just wanted to know if there was a lib for this or that i just could use those procs .. cause its in a lib (tcllib) then it would be stupid to copy it then i just could do package require

i always wana make sur sorry for the stupid questions

[strikelight]

s'alright..