Implement getters/setters for types in generic procedures

[mdpiper]

In Fortran, the type and rank of an argument must be known at compile time. This implies that we need BMI getters and setters for each intrinsic type that a model may use (i.e., get_value_int, get_value_float, get_value_double, etc.). However, we can simplify calls to the getters and setters by defining generic procedure interfaces with implementations for all the types that we expect to be passed at runtime. The user would only have to call get_value, and not be concerned with type. The model developer writing a BMI would still have to write get_value_int, get_value_float, etc.

For this issue, I'll implement the following methods:

• [x] get_value_int
• [x] get_value_float
• [x] get_value_double
• [x] get_value_ref_int
• [x] get_value_ref_float
• [x] get_value_ref_double
• [x] get_value_at_indices_int
• [x] get_value_at_indices_float
• [x] get_value_at_indices_double
• [x] set_value_int
• [x] set_value_float
• [x] set_value_double
• [x] set_value_at_indices_int
• [x] set_value_at_indices_float
• [x] set_value_at_indices_double

I'll leave long and complex types for a separate, deferred, issue.

cc @sc0tts, @mcflugen

[mcflugen]

This is how babel maps SIDL types to Fortran data types. Would it make sense to just use these names? So, get_value_int, get_value_bool, etc.

SIDL type	Real Fortran 2003/2008 type
int	integer(c_int32_t) integer(kind=sidl_int)
long	integer(c_int64_t)
float	real(c_float)
double	real(c_double)
bool	integer(c_int)
char	integer(c_signed_char)
string	type(c_ptr)
fcomplex	complex(c_float_complex)
dcomplex	complex(c_double_complex)

Or we could use the LAPACK naming scheme. So get_value_s (or get_svalue?), etc.

lapack code	Fortran name
S	REAL
D	DOUBLE PRECISION
C	COMPLEX
Z	COMPLEX*16 or DOUBLE COMPLEX

[mdpiper]

I like the SIDL types.

Thank you also for the link to the Babel docs. I'll see what else is there that I can use.

[sc0tts]

Are integers always signed 32-bit integers?

Also deferred we might want shorts, and unsigned versions (and bytes (C's unsigned chars)).

[mdpiper]

Closed with #17.