Fixed-Point Toolbox™

sub - Subtract two objects using fimath object

Syntax

c = F.sub(a,b)

Description

c = F.sub(a,b) subtracts objects a and b using fimath object F. This is helpful in cases when you want to override the fimath objects of a and b, or if the fimath objects of a and b are different.

a and b must have the same dimensions unless one is a scalar. If either a or b is scalar, then c has the dimensions of the nonscalar object.

If either a or b is a fi object, and the other is a MATLAB^® built-in numeric type, then the built-in object is cast to the word length of the fi object, preserving best-precision fraction length.

Examples

In this example, c is the 32-bit difference of a and b with fraction length 16.

a = fi(pi);
b = fi(exp(1));
F = fimath('SumMode','SpecifyPrecision',...
		'SumWordLength',32,'SumFractionLength',16);
c = F.sub(a, b) 

c =
 
    0.4233


          DataTypeMode: Fixed-point: binary point scaling
                Signed: true
            WordLength: 32
        FractionLength: 16

             RoundMode: nearest
          OverflowMode: saturate
           ProductMode: FullPrecision
  MaxProductWordLength: 128
               SumMode: SpecifyPrecision
         SumWordLength: 32
     SumFractionLength: 16
         CastBeforeSum: true

Algorithm

c = F.sub(a,b) is equivalent to

a.fimath = F;
b.fimath = F;
c = a - b;

except that the fimath properties of a and b are not modified when you use the functional form.

See Also

add, divide, fi, fimath, mpy, numerictype

stripscaling

subsasgn