Real number in while loop in bash -

i while loop in bash, using real numbers, gives me errors. whatever try , find on internet doesn't fix problem.

here problematic part of code: (energy find command energy=$(echo "$real1 - $real2" | bc -l)

energy=${energy#-} deltae=$(echo "$energy"  | bc -l) echo $energy echo $deltae  while (( $deltae > 0.0001 )); 

of course there after "do" execution stops here. gives me following error :

1.999655175151897025 1.999655175151897025 ./run_ilda.sh: line 99: ((: 1.999655175151897025 > 0.0001 : syntax error: invalid arithmetic operator (error token ".999655175151897025 > 0.0001 ") 

and without $ :

while (( deltae > 0.0001 )); 

it gives

1.999655175151897025 1.999655175151897025 ./run_ilda.sh: line 99: ((: 1.999655175151897025: syntax error: invalid arithmetic operator (error token ".999655175151897025") 

i tried :

while [  $deltae -gt 0.0001 ] 

and gives me :

1.999655175151897025 1.999655175151897025 ./run_ilda.sh: line 99: [: 1.999655175151897025: integer expression expected 

does know what's going on , how fix this?

use bc evaluate comparison:

if (( $(echo "$deltae > 0.0001" | bc -l) ));     ... fi