Illegal float value "error" c-shell

Question

I have a form made it with a couple of text boxes, in which I input floating numbers and use this number to sum with other text box and put the result in a label.

I then input the values of the text boxes to a variable (xbiz and xbder) and I sum it for example I get then this result : xbiz = 5.2 xbder = 2.3

My problem is when one of the text boxes is empty (in blank) the script give me an error of "ILLEGAL FLOAT VALUE!" I mean if I am not input a value in any od the two variables

How can solve this problem?

Here is my code:

#FORM
echo "FG 999999" >> $gui_in
echo "FONT cbr18" >> $gui_in
echo "BG 901010" >> $gui_in
echo "LABEL LOCATINES" >> $gui_in
echo "FG 101090" >> $gui_in
echo "FONT cbr18" >> $gui_in
echo "BG 708787" >> $gui_in

echo "TEXT xbiz X_BOT_IZQ" >> $gui_in
echo "TEXT xbder X_BOT_DER" >> $gui_in

#Calculation
set varx = `echo " $xbder + $xbiz" | bc -l`


#After calculate the values of the two variables (xbder + xbiz) I use the result in the following line:

COM display_layer,name=comp,display=yes,number=1
COM add_pad,attributes=no,**x=${varx},y=${varx}**,symbol=${sizefido},polarity=positive,\
angle=0,mirror=no,nx=1,ny=1,dx=0,dy=0,xscale=1,yscale=1

Answer 1

If xbiz or xbder is empty, bc will complain (bash here)

$ echo "5.2 + " | bc -l
(standard_in) 2: syntax error

You're going to need something like (untested)

if (! $?xbiz) set xbiz = 0
set varx = `echo " 5.2 + $xbiz" | bc -l`
if (! $?xbder) set xbder = 0
set vary = `echo " 5.2 + $xbder" | bc -l`