pseudocode:Random walk equation
    year rate =      good year rate * term chance(1 in n)
                plus normal year rate * term chance(1 in n)
                plus bad year rate * term chance(1 in n)
                plus place holder to keep from all zeroed terms
    pseudocode: set chance terms initially to zero until activated.
    pseudocode:   if      rand() <  $side2 , set term1 1  
    pseudocode: if no chance terms fire, year of zero interest will result.
    pseudocode: good/norm/bad years loaded as $side1,$side2,$side3 from form.
    current = .01*$side1*$term1+.01*$side3*$term2+.01*$side5*$term3+.00000000001 } ]  
    pseudocode: add $current sum of terms for 1 to N years in for loop
    pseudocode:  and divide by N years from $side7 in form  
    pseudocode:  load results into   answer fields 

    # pretty print from autoindentation and ased editor
    # random walk equation
    # written on Windowws XP on eTCL
    # working under TCL version 8.5.6 and eTCL 1.0.1
    # gold on TCL WIKI , 24aug2010
    package require Tk
    frame .frame -relief flat -bg aquamarine4
    pack .frame -side top -fill y -anchor center
    
    set names {{} {good year rate:} {1 in chance:} {normal year rate} {1 in chance:} {bad year rate:} {1 in chance} {1 to N years:} { answer:} }
    foreach i {1 2 3 4 5 6 7 8} {
        label .frame.label$i -text [lindex $names $i] -anchor e
        entry .frame.entry$i -width 35 -textvariable side$i
        grid .frame.label$i .frame.entry$i -sticky ew -pady 2 -padx 1
    }
    proc about {} {
        set msg "Calculator for Random Walk Equation.
        from TCL WIKI,
        written on eTCL "
        
        tk_messageBox -title "About" -message $msg
    }
    proc pi {} {expr acos(-1)}
    
    proc interlinear { xx1 yy1 xx3 yy3 xx2   } {
        return [expr {  ((($xx2-$xx1)*($yy3-$yy1))/($xx3-$xx1))+ $yy1 } ] ;}
    
    proc pol { xx1 yy1 xx3 yy3 xx2   } {
        return [expr {  ((($xx2-$xx1)*($yy3-$yy1))/($xx3-$xx1))+ $yy1 } ] ;}
    
    proc errorx  {aa bb} {expr { $aa > $bb ?   (($aa*1.)/$bb -1.)*100. : (($bb*1.)/$aa -1.)*100.}}
    
    proc height5 { aa bb cc } {
        set bb [ expr { $cc*[pi]/180.  } ]
        set cc [ expr { $cc*[pi]/180.  } ]
        set dd  [ expr { 1.*$aa*tan($bb)*tan($cc)/( tan($cc)-tan($bb))} ]
        return $dd
    }
    
    proc intelligent5 { xx1   } {
        global side1 side2 side3
        global side4 side5 side6 side7 side8
        set term1 0
        set term2 0
        set term3 0
        set current 0
        set chance1 [expr {1./$side2 }]
        set totyears [expr {int($side7) }]
        for {set i 0;} {$i<$totyears} {incr i} {
            if { [ expr { rand() } ] <= $side2 } {set term1 1 }
            if { [ expr { rand() } ] <= $side4 } {set term2 1 }
            if { [ expr { rand() } ] <= $side6 } {set term3 1 }
            
            set current  [ expr { ($current*1.) +.01*$side1*$term1+.01*$side3*$term2+.01*$side5*$term3+.00000000001 } ]
            
        }
        set side7 $totyears
        set side8  [expr {($current*1.)/$totyears }]
        
        if { [ expr { abs($side8) } ] <= .0001 } {set side8 0 }
        return $side8
    }
    
    proc calculate {     } {
        global colorwarning
        global colorback
        global answer2   answer3
        global side1 side2 side3 side4 side5 side6 side7 side8
        set answer2 5
        
        set answer2  [ intelligent5  $side8     ]
        
        set side8 $answer2
        
    }
    proc fillup {aa bb cc dd ee ff gg hh} {
        
        .frame.entry1 insert 0 "$aa"
        .frame.entry2 insert 0 "$bb"
        .frame.entry3 insert 0 "$cc"
        .frame.entry4 insert 0 "$dd"
        .frame.entry5 insert 0 "$ee"
        .frame.entry6 insert 0 "$ff "
        .frame.entry7 insert 0 "$gg "
        .frame.entry8 insert 0 "$hh "
        
    }
    
    proc clearx {} {
        foreach i {1 2 3 4 5 6 7 8} {
            .frame.entry$i delete 0 end
        }
    }
    
    proc reportx {} {
        global side1 side2 side3 side4 side5 side6 side7 side8
        console show;
        puts "
        The interpolation function takes
        two know points on a line and
        solves for an intermediate point.
        The points are xx1,yy1   xx2,yy2 and xx3,?yy3?
        The input order of the five items
        is xx1 yy1 xx2 yy2 xx3
        and solving for ?yy3?.
        The interpolation function loaded as
        proc pol. User should be able to write
        pol 50. 1000. 200. 1200.  150.
        and save answer (1133.3)  on console."
        puts " $side1     "
        puts " $side2    "
        puts " $side3   "
        puts " $side4     "
        puts " $side5     "
        puts " $side6     "
        puts " $side7    "
        puts " $side1     "
        puts " $side2    "
        puts " $side3    "
        puts " $side4    "
        puts " $side5    "
        puts " $side6    "
        puts " $side7    "
        puts " $side8    "
        puts "answer   $side8 "
    }
    
    frame .buttons -bg aquamarine4
    
    ::ttk::button .calculator -text "Solve" -command { calculate   }
    
    ::ttk::button .test2 -text "Testcase1" -command {clearx;fillup 10. .333 5. .333  -10. .333  1. 1.}
    ::ttk::button .test3 -text "Testcase2" -command {clearx;fillup 10. .333 5. .333  -10. .333  7.7 1.  }
    ::ttk::button .test4 -text "Testcase3" -command {clearx;fillup  10. .333 5. .333  -10. .333  8.5 1.  }
    ::ttk::button .clearallx -text clear -command {clearx  }
    ::ttk::button .about -text about -command about
    ::ttk::button .cons -text report -command { reportx }
    ::ttk::button .exit -text exit -command {exit}
    pack .calculator  -in .buttons -side top -padx 10 -pady 5
    
    pack  .clearallx .cons .about .exit .test4 .test3  .test2   -side bottom -in .buttons
    grid .frame .buttons -sticky ns -pady {0 10}
    . configure -background aquamarine4 -highlightcolor brown -relief raised -border 30
    bind . <Motion> {wm title . "Random Walk Equation Calculator "}