How do I print the "zero" between the minus and the decimal places on Bash shell

Question

With dc external tool bash tend to not print at the right of the decimal point.

#!/bin/bash    
a[0]=-0.5    
`echo "scale=10;${a[0]}/1"|bc -l`

With the command represented above bash will print -.5000000000.

How can I add the zero between the minus signal and the point -0.5000000000

PS: I do print a[1]=0 with 10 decimal cases?

Answer 1

Instead of bc you may consider this awk that does floating point match and formatting using printf:

a[0]=-0.5

awk -v n="${a[0]}" 'BEGIN{printf "%.10f\n", n/1}'

-0.5000000000