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Warning (10542): VHDL Variable Declaration warning at math_real.vhd(2373): used initial value expression for variable "RECIPROCAL" because variable was never assigned a value
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The reason for the warning is lines like this in math_real-body.vhdl (downloadable from the IEEE web site):
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variable RECIPROCAL: BOOLEAN := X < 0.0;-- Check sign of argument
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This should be 'constant'.
Given that this is in the IEEE library code, I don't think you can really do much about it. You might be able to recompile the IEEE libraries to over-ride whatever Quartus uses internally.
Cheers,
Dave