| msg179378 - (view) |
Author: Vladimir Rutsky (rutsky) |
Date: 2013-01-08 22:06 |
| It would be nice if Python will be able to access variables with C99 complex types through ctypes module. |
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| msg179459 - (view) |
Author: Amaury Forgeot d'Arc (amaury.forgeotdarc) *  |
Date: 2013-01-09 15:48 |
| libffi still has no support for _Complex. Did you try with a pure Python solution, like the one suggested in http://objectmix.com/python/112374-re-ctypes-c99-complex-numbers.html |
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| msg179609 - (view) |
Author: Vladimir Rutsky (rutsky) |
Date: 2013-01-11 00:45 |
| Yes, I managed to pass and operate with matrices of complex numbers to pure C and Fortran programs by using Numpy and their ctype adapters (only for whole matrices, they don't provide c_complex type; in general see http://www.scipy.org/Cookbook/Ctypes for details). I suppose pure python solution that suggested in provided by you link works too: class Complex64(Structure): _fields_ = [("real", c_float), ("imag", c_float)] But I'm unsure is this is expected behavior or luck, and on some platform this code will not work due to different complex numbers internal representation. Any way this should be implemented in libffi first, and then in ctypes, so this feature request should be postponed, IMO. |
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| msg179646 - (view) |
Author: Mark Dickinson (mark.dickinson) * |
Date: 2013-01-11 08:24 |
| > But I'm unsure is this is expected behavior or luck, and on some > platform this code will not work due to different complex numbers > internal representation. What platform? Isn't the complex number representation standard? E.g., C99 6.2.5p13 says: "Each complex type has the same representation and alignment requirements as an array type containing exactly two elements of the corresponding real type; the first element is equal to the real part, and the second element to the imaginary part, of the complex number." |
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| msg180759 - (view) |
Author: Mark Dickinson (mark.dickinson) * |
Date: 2013-01-27 10:40 |
| Postponing as suggested. |
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| msg285961 - (view) |
Author: Tom Krauss (Tom Krauss) |
Date: 2017-01-21 16:37 |
| I'm trying to add support for this in cffi, which uses ctypes... apparently this is now supported in libffi (https://github.com/libffi/libffi, v3.2 Nov 2014). It would be nice if this issue could be re-opened, or another one created for the same purpose. |
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| msg285998 - (view) |
Author: Mark Dickinson (mark.dickinson) * |
Date: 2017-01-22 08:23 |
| Thanks, Tom. Re-opening. |
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| msg286453 - (view) |
Author: Armin Rigo (arigo) * |
Date: 2017-01-29 22:23 |
| * Tom: the issue is unrelated to cffi, but both ctypes and cffi could proceed to support C complexes, now that libffi support has been added. * Mark: the problem is that the text you quote from the C standard fixes the representation of a complex in memory, but doesn't say anything about directly passing a complex as argument or return value to a function call. Platforms use custom ways to do that. The text you quote says a complex is an array of two real numbers; but passing an array as argument to a function works by passing a pointer to the first element. Typically, this is not how complexes are passed: instead, some pointerless form of "passing two real numbers" is used. |
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| msg321046 - (view) |
Author: Reid (rkmountainguy) |
Date: 2018-07-04 14:47 |
| I concur with rutsky. Complex numbers are essential in the physical sciences, and the complex type is part of the c99 standard. Trying to shoehorn complex support by a user-defined type makes use of the builtin methods for the standard complex type clunky. |
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| msg321049 - (view) |
Author: Armin Rigo (arigo) * |
Date: 2018-07-04 15:01 |
| cffi supports complex numbers since release 1.11---for direct calls using the API mode. That means that neither CFFI's ABI mode, nor ctypes, can possibly work yet. The problem is still libffi's own support, which is still not implemented (apart on a very uncommon CPU architecture, the s390). |
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