Status: New
Owner: ----
Labels: Type-Defect Priority-Medium
New issue 1487 by Toon.Verstraelen: fcode: print sympy expressions as
Fortran code
http://code.google.com/p/sympy/issues/detail?id=1487
Hi,
The patch is rather trivial for now. It just serves as a basic starting
point for further extensions and testing with the codegen.
I have a few questions related to ccode and fcode:
* Should an exception be raised when ccode or fcode encounter a function
that is not supported in the standard definitions of the C and Fortran
language? (I'm pro raising an exception.) We can introduce an optional
argument, user_functions={}, for fcode and ccode. This list contains the
names user-defined functions that the printer should not complain about.
A few examples:
In [15]: ccode(integrate(sin(x)/x,x))
Out[15]: Integral(sin(x)/x, x)
This should always raise an exception. Such a thing is never ever going to
be compilable.
In [22]: ccode(gamma(x))
Out[22]: gamma(x)
This should also raise an error since the gamma function is not part of the
C standard. We can provide a way around the issue:
In [23]: ccode(gamma(x), user_functions={gamma: 'gsl_sf_gamma'})
Out[23]: gsl_sf_gamma(x)
Is this acceptable?
* What to do with sympy constants that are not part of the language? A
typical example in Fortran is the constant pi. In a normal program, it has
to be defined by the programmer in this style:
REAL (KIND=dp), PARAMETER :: pi = 3.14159265358979323846264338_dp
We can replace them by their numerical value in the printer, but this is a
bit messy. How are we going to determine the precision to be used? We can
probably think of more fancy solutions at the codegen level, but the
printer on itself should also give an acceptable result.
* ccode has an implementation for Piecewise functions that does not return
a single expression, but multiple statements. This is not compatible with
the assumptions made by the codegen. We can replace this by a conditional
operator:
http://en.wikipedia.org/wiki/Conditional_operator
Any comments?
Attachments:
0001-fcode-print-sympy-expressions-as-Fortran-code.patch.gz 1.6 KB
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