Hi,
I'm reading C Primer Plus by Prata, and he mentioned that if you initilize a variable with static storage duration, then you have to use constant values. I don't understand what he means by 'constant values'. Did he mean that I have to declare my variable with the qualifier "const"?
Actually, there is no such requirement.Originally Posted by nimitzhunter
Code:#include <cmath> #include <complex> bool euler_flip(bool value) { return std::pow ( std::complex<float>(std::exp(1.0)), std::complex<float>(0, 1) * std::complex<float>(std::atan(1.0) *(1 << (value + 2))) ).real() < 0; }
No, it means that you should say, use a literal, or an expression that can be resolved as if it were a literal, to initialise an object with static storage duration. It does not mean that all variables with static storage duration must be declared const.
Actually, there is:
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Heheh. I think this is the second time you've pointed that out to me, too.
Why then does GCC not complain with this code?
Code:int bar( void ) { } int main( void ) { static int foo = bar( ); }
Code:#include <cmath> #include <complex> bool euler_flip(bool value) { return std::pow ( std::complex<float>(std::exp(1.0)), std::complex<float>(0, 1) * std::complex<float>(std::atan(1.0) *(1 << (value + 2))) ).real() < 0; }
But it does...
at least for the MinGW port of gcc 3.4.5 with the -pedantic option.Code:test.c: In function `main': test.c:6: error: initializer element is not constant
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I see. Yeah, I haven't got the "pedantic" switch enabled, apparently (fixed). I wonder why it's required, anyway? Related to initialization order not being guaranteed WRT different translation units or some such?
Code:#include <cmath> #include <complex> bool euler_flip(bool value) { return std::pow ( std::complex<float>(std::exp(1.0)), std::complex<float>(0, 1) * std::complex<float>(std::atan(1.0) *(1 << (value + 2))) ).real() < 0; }
