April 07, 2003 Using the fldpi instruction for PI (3.1415...) | ||||
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/* If anyone has been trying to get the cool tip for using pi using the fldpi instruction rather than defining it as a constant from the May 2003 C++ User Journal on DMC, here is the trick. You need to declare x as static below. Enjoy! I don't know if there is any advantage to getting pi this way, but it's interesting. */ #include <stdio.h> class CPi { public: operator double () const { static double x; // the "static" is necessary for DMC! // otherwise, the asm block seems to do nothing. asm { fldpi; // push the constant pi to the x87 stack fst x; // store to x } return x; } }; static CPi PI; main() { double x; printf("Hello \n"); x = PI; // cool. Looks like a constant, but it's a function call. printf("Pi = %f\n", x); } |
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