floating point - PHP & Base 2. Which Floats give a precise Value? -


apologies poor maths skills, i've tried understand answer own query i'm not convinced.

we know php doesn't store floats in base 10 base 2.

i have series of calculations using 0.5 float, , in trying understand if stored 0.500001 or 0.4999999 (for rounding purposes there big difference!!!) have come understand 0.5 stored precisely in base2.

my queries

a have understood correctly?

b other floats stored precisely in base2? eg 0.25?

any multiple of 1/pow(x, 2) can precisely represented float.

that means x/2, x/4, x/8, x/16 ...ect. can accurately represented.

for more information on how floating point numbers store see http://kipirvine.com/asm/workbook/floating_tut.htm

gmp library high precision math.


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