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I am writing a small piece of Fortran 90 code to compute some quantities using complex variables.
I have a subroutine with the following instructions:
complex, dimension(3) :: v
integer :: i
real:: tmp
do i = 1,3
tmp = vg(i)
v(i) = (tmp, 0.0)
enddo
v is a complex array of length 3. vg is an array of length 3 too whose elements are real.
When I compile the above code with gfortran 4.7.3 I get the following error:
v(i) = (tmp,0.0)
Error: Expected PARAMETER symbol in complex constant at (1)
I do not understand what's the problem.
253
The PARAMETER statement assigns a symbolic name to a constant. In this alternate form, the type of the constant expression determines the type of the name; no conversion is done.
Add PARAMETER in front of the double colon (::) and use a comma to separate the type name (i.e., REAL) and the word PARAMETER. Following each name, one should add an equal sign (=) followed by an expression. The value of this expression is then assigned the indicated name.
A literal constant is a datum whose value cannot change throughout the program unit. The form of the string representing a constant determines the value and data type of the constant. (For a named constant, defined by a PARAMETER statement, the name defines the data type.)
You have to use
v(i) = cmplx(tmp, 0.0)
Your syntax (re, im) works only for constant expressions, i.e. when re and im are real or integer constants.
This means you cannot make a complex constant from a real variable and a real constant. You have to use the intrinsic function cmplx which converts real variables to complex ones, or builds complex variables from pairs of real variables (or integer).
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