#!wish

toplevel .bias_p

global K1 
global K2
global alpha
global conv
global v
global w

set K1 -2
set K2 1

set alpha 1

proc skip_args3 { a b c } { }

proc recompute_conv {} {
global K1 
global K2
global alpha
global conv
set conv "ERROR"
if { [ catch {
	set Q [expr $K2-$K1 ]
	if { $Q < 1 } { 
		# signal error
		expr 1/0 
		}
	set conv 0.0
	for { set i 1 } { $i <= $Q } { incr i } {
		set conv [expr $conv + ($Q-$i+1.0)*pow($i, $alpha)]
		}
	set conv [expr 2.0*$conv/($Q*($Q+1))]
	} ] } { set conv "ERROR" }
.bias_p.conv configure -text "Conversion factor: w/v=$conv"	
}

label .bias_p.l2  -text "Upper bias limit"
entry .bias_p.e2  -textvariable K2
grid .bias_p.l2 .bias_p.e2 -sticky news

label .bias_p.l1  -text "Lower bias limit"
entry .bias_p.e1  -textvariable K1
grid .bias_p.l1 .bias_p.e1 -sticky news

label .bias_p.l3  -text "Alpha"
entry .bias_p.e3  -textvariable alpha
grid .bias_p.l3 .bias_p.e3 -sticky news

label .bias_p.conv -background gray 
grid .bias_p.conv - -sticky news -padx 3 -pady 3

label .bias_p.l4  -text "v (jump)"
entry .bias_p.e4  -textvariable v
grid .bias_p.l4 .bias_p.e4 -sticky news

label .bias_p.l5  -text "w (walk)"
entry .bias_p.e5  -textvariable w
grid .bias_p.l5 .bias_p.e5 -sticky news

frame .bias_p.f -background gray

button .bias_p.f.b1 -text "Convert v to w" -command {
	if { [catch {
		set w [expr $v * $conv ]
		} ] } { set w "ERROR" }
	}
button .bias_p.f.b2 -text "Convert w to v" -command {
	if { [catch {
		set v [expr $w / $conv ]
		} ] } { set w "ERROR" }
	}

grid .bias_p.f.b1 .bias_p.f.b2 -padx 10 -pady 8

grid .bias_p.f - -sticky news -pady 3 -padx 3

recompute_conv

trace variable K1 w { recompute_conv; skip_args3 }
trace variable K2 w { recompute_conv; skip_args3 }
trace variable alpha w { recompute_conv; skip_args3 }

wm title .bias_p "Volatility converter"