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cintunary-operator

Invalid type argument of unary '*' (have int?

I have read other questions like this but none seemed to work... My code is:

int flowRateFormula(int pipeDiameter,double velocity)
{
int integer3;

integer3=PI*(1/4)*(pow(pipeDiameter,2))*velocity;

return integer3;

 }

And the error is:

flowRate.c: In function ‘flowRateFormula’:
flowRate.c:38:13: error: invalid type argument of unary ‘*’ (have ‘int’)

What to do? BTW PI IS DEFINED

Solution

  • Most likely you have the line

    #define PI

    somewhere, which causes your code to be equivalent to:

    integer3=*(1/4)*....

    and this fails to compile. Replace it with e.g.

    #define PI 3.1416

    Note also that (1/4) will be evaluated to 0, because integer division returns an integer. you probably want to use 1.0/4.0.