How to output float result?

I am working on bash script: need to evaluate an input and then output the result
as a float *.xxx:
I do:

read var1
var2=$((var1))
#echo $var2
echo $((var1))

an input: 5+503/20 + (192)/7
my output is 17 but it should 17.929

How to evaluate it as a float?

>Solution :

Bash only supports integer arithmetic.

In your case, you can use bc(1).

read var1
var2="$(bc <<<"scale=2;$var1")"

Use the scale variable in bc(1) to set the number of significant digits (default with is 0).