How to use float numbers on BusyBox?

I have a little computer with BusyBox, and compiling anything on it is a nightmare.

I want to do something simple like "0,5*2", but can't without additional software.

I tried "expr", "let", and just can't do any operation with float numb开发者_Python百科ers.

Is there anything I can do?

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busybox should have awk.

awk 'BEGIN{print 0.5*2}' 

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busybox has dc built in. Here's a link to all of the documentation.