[GWM] Presents a number of cards - you select Yes or No to check if your imagined number is there.  
After 6 questions the number you thought of is displayed.  
A classic automatic magic trick often used in Christmas Crackers.

Unless you gave an incorrect answer, when the result is GiGo - Garbage In, Garbage Out. 
This variation allows a range of choice other than 0-64 or 0-128 etc. 
The technique is identical in every way (but looks cleverer) than simple binary splitting - 
'is your number <50? (Yes - is number <25; no:is number <75) until you halve your way to the target.


 # 'magic' interactive eneration of magic cards trick
 global sum
 proc addresult {nres onoff nmax} {
	global sum
	if {$onoff == 1} {
	 	incr sum $nres
	}
	 incr  nres $nres
	puts "Result $sum $nres"
	makeCard $nmax $nres
 }

 proc showresult {nmax} {
	global sum
    catch {destroy .bguess} {} ;
  catch {destroy .t} {} ;# delete it. Same as clear.
   catch {destroy .byes} {} ;
   catch {destroy .bno} {} ;
   catch {destroy .end} {} ;
	button .bguess   -text "Your number was\n$sum" -command "givehelp $nmax" -font {Arial 32 bold}
	pack .bguess
 }
 proc givehelp {nmax} {
	global sum
    catch {destroy .bguess} {} ;
  catch {destroy .t} {} ;# delete it. Same as clear.
   catch {destroy .byes} {} ;
   catch {destroy .bno} {} ;
   catch {destroy .end} {} ;
	button .bguess   -text "Choose a number between\n0 & $nmax" -command "runtrick $nmax" -font {Arial 32 bold}
	pack .bguess
 }

 proc makeCard {nmax ntest} {
   catch {destroy .bguess} {} ;
   catch {destroy .t} {} ;# delete it. Same as clear.
   catch {destroy .byes} {} ;
   catch {destroy .bno} {} ;
   catch {destroy .end} {} ;

 if { $nmax >$ntest } {
  text .t  -bg beige
  button .byes   -text "Yes" -command "addresult $ntest 1 $nmax"
  button .bno   -text "No" -command "addresult $ntest 0 $nmax"
  button .end   -text "Quit" -command "exit"
  pack .t .byes .bno .end
  pack .byes .bno .end -side left
  .t insert end "Is your number in this set:\n"
  set i 1
	set nextnewl 10
	while {$i<$nmax} {
		set frac [expr (($i/$ntest))]
		if {[expr $frac%2==1 ] } {
			.t insert end " $i"
		}
		incr i
		if {$i>$nextnewl} {
			.t insert end "\n"
	incr nextnewl 10
		}
	}
	} else {
		showresult  $nmax
	}
 }

 proc runtrick {nmax} {
	global sum
	set sum 0
	
	makeCard $nmax 1
 }
 proc starttrick {nmax} {
	givehelp $nmax
 }

 set sum 0
 starttrick 100
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[Category Education] -
[Category Games]