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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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CPROJ(3P) POSIX Programmer's Manual CPROJ(3P)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
cproj, cprojf, cprojl — complex projection functions
#include <complex.h>
double complex cproj(double complex z);
float complex cprojf(float complex z);
long double complex cprojl(long double complex z);
The functionality described on this reference page is aligned with
the ISO C standard. Any conflict between the requirements
described here and the ISO C standard is unintentional. This
volume of POSIX.1‐2017 defers to the ISO C standard.
These functions shall compute a projection of z onto the Riemann
sphere: z projects to z, except that all complex infinities (even
those with one infinite part and one NaN part) project to positive
infinity on the real axis. If z has an infinite part, then
cproj(z) shall be equivalent to:
INFINITY + I * copysign(0.0, cimag(z))
These functions shall return the value of the projection onto the
Riemann sphere.
No errors are defined.
The following sections are informative.
None.
None.
Two topologies are commonly used in complex mathematics: the
complex plane with its continuum of infinities, and the Riemann
sphere with its single infinity. The complex plane is better
suited for transcendental functions, the Riemann sphere for
algebraic functions. The complex types with their multiplicity of
infinities provide a useful (though imperfect) model for the
complex plane. The cproj() function helps model the Riemann sphere
by mapping all infinities to one, and should be used just before
any operation, especially comparisons, that might give spurious
results for any of the other infinities. Note that a complex value
with one infinite part and one NaN part is regarded as an
infinity, not a NaN, because if one part is infinite, the complex
value is infinite independent of the value of the other part. For
the same reason, cabs() returns an infinity if its argument has an
infinite part and a NaN part.
None.
carg(3p), cimag(3p), conj(3p), creal(3p)
The Base Definitions volume of POSIX.1‐2017, complex.h(0p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics Engineers,
Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard,
the original IEEE and The Open Group Standard is the referee
document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 CPROJ(3P)
Pages that refer to this page: complex.h(0p), carg(3p), cimag(3p), conj(3p), creal(3p)
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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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