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GNU Info (gcc-295.info)ComplexComplex Numbers =============== GNU C supports complex data types. You can declare both complex integer types and complex floating types, using the keyword `__complex__'. For example, `__complex__ double x;' declares `x' as a variable whose real part and imaginary part are both of type `double'. `__complex__ short int y;' declares `y' to have real and imaginary parts of type `short int'; this is not likely to be useful, but it shows that the set of complex types is complete. To write a constant with a complex data type, use the suffix `i' or `j' (either one; they are equivalent). For example, `2.5fi' has type `__complex__ float' and `3i' has type `__complex__ int'. Such a constant always has a pure imaginary value, but you can form any complex value you like by adding one to a real constant. To extract the real part of a complex-valued expression EXP, write `__real__ EXP'. Likewise, use `__imag__' to extract the imaginary part. The operator `~' performs complex conjugation when used on a value with a complex type. GNU CC can allocate complex automatic variables in a noncontiguous fashion; it's even possible for the real part to be in a register while the imaginary part is on the stack (or vice-versa). None of the supported debugging info formats has a way to represent noncontiguous allocation like this, so GNU CC describes a noncontiguous complex variable as if it were two separate variables of noncomplex type. If the variable's actual name is `foo', the two fictitious variables are named `foo$real' and `foo$imag'. You can examine and set these two fictitious variables with your debugger. A future version of GDB will know how to recognize such pairs and treat them as a single variable with a complex type. automatically generated by info2www version 1.2.2.9 |