passing lua numbers to a C function that takes float values

Subject: passing lua numbers to a C function that takes float values
From: &quot;Aaron Saarela&quot; &lt;Aaron.Saarela@ ... &gt;
Date: Thu, 8 May 2008 17:22:51 -0400

Thanks to everyone that helped out with my yield problem earlier. I’ve reworked my app and solved that problem.

My next problem is related to passing float values between C++ and Lua. I have a number in Lua (“8.2008” in particular). If I call another Lua function with this value, it remains consistent. When I call a C function that takes a float with this value, however, it’s received as ‘8.2007999999999992”. If I pass this value back to Lua (using lua_pushnumber), it becomes ‘8.2007999420166’. And so on. I’m loosing precision on each Lua / C transition.

I’m using Lua 5.1.3 with the lnum patch (double, int64). My conversions are done via SWIG 1.3.31 wrappers.

Is this just a side-effect of the conversion between double and float or is there a way around this?

Thanks,

-Aaron