to_float() "right bound of range must be a constant" error

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I worked around this problem by converting the integer to unsigned. To convert integer to unsigned or signed data type over,

use IEEE.NUMERIC_STD.all;you must use,

to_unsigned(I,U’length);to_signed(I,S’length)where I is the integer value and U'length is the unsigned vector length ( the number of bit ).

The to_float(unsigned) function doesn't cause any problems.

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This wont help, as the problem is with the non-constant loop bounds