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-rw-r--r--libdimension/dimension/polynomial.h35
1 files changed, 31 insertions, 4 deletions
diff --git a/libdimension/dimension/polynomial.h b/libdimension/dimension/polynomial.h
index 56e3ac0..b0a9357 100644
--- a/libdimension/dimension/polynomial.h
+++ b/libdimension/dimension/polynomial.h
@@ -18,7 +18,8 @@
* <http://www.gnu.org/licenses/>. *
*************************************************************************/
-/*
+/**
+ * @file
* Utility functions for working with and numerically solving polynomials.
* Polynomials are represented as simple arrays where the ith element is the
* coefficient on x^i. In general, we are only interested in positive roots.
@@ -30,6 +31,14 @@
#include <stddef.h>
#include <stdio.h>
+/**
+ * Evaluate a polynomial at \p x.
+ * @param[in] poly The coefficients of the polynomial to evaluate, in order
+ * from lowest degree to highest degree. The array should
+ * have dimension <tt>degree + 1</tt>.
+ * @param[in] degree The degree of the polynomial.
+ * @param[in] x The value of the variable at which to evaluate.
+ */
DMNSN_INLINE double
dmnsn_evaluate_polynomial(const double poly[], size_t degree, double x)
{
@@ -41,6 +50,12 @@ dmnsn_evaluate_polynomial(const double poly[], size_t degree, double x)
return ret;
}
+/**
+ * Evaluate the derivative of a polynomial at \p x.
+ * @param[in] poly The coefficients of the polynomial to evaluate.
+ * @param[in] degree The degree of the polynomial.
+ * @param[in] x The value of the variable at which to evaluate.
+ */
DMNSN_INLINE double
dmnsn_evaluate_polynomial_derivative(const double poly[], size_t degree,
double x)
@@ -53,11 +68,23 @@ dmnsn_evaluate_polynomial_derivative(const double poly[], size_t degree,
return ret;
}
-/* Stores the positive roots of poly[] in x[], and returns the number of such
- roots that were stored */
+/**
+ * Find the positive roots of a polynomial.
+ * @param[in] poly The coefficients of the polynomial to solve.
+ * @param[in] degree The degree of the polynomial.
+ * @param[out] x An array in which to store the roots. It should have
+ * dimension \p degree.
+ * @return The number of positive roots stored in \c x[].
+ */
size_t dmnsn_solve_polynomial(const double poly[], size_t degree, double x[]);
-/* Helper function to print a polynomial */
+/**
+ * Output a polynomial. The polynomial is printed as a function of x suitable
+ * for input into a CAS, and without a trailing newline.
+ * @param[in,out] file The file to write to.
+ * @param[in] poly The coefficients of the polynomial to print.
+ * @param[in] degree The degree of the polynomial.
+ */
void dmnsn_print_polynomial(FILE *file, const double poly[], size_t degree);
#endif /* DIMENSION_POLYNOMIAL_H */