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<TITLE>CLN, a Class Library for Numbers - 9. Univariate polynomials</TITLE></HEAD><BODY>Go to the <A HREF="cln_1.html">first</A>, <A HREF="cln_8.html">previous</A>, <A HREF="cln_10.html">next</A>, <A HREF="cln_13.html">last</A> section, <A HREF="cln_toc.html">table of contents</A>.<P><HR><P>
<H1><A NAME="SEC54" HREF="cln_toc.html#TOC54">9. Univariate polynomials</A></H1><P><A NAME="IDX269"></A><A NAME="IDX270"></A>
<H2><A NAME="SEC55" HREF="cln_toc.html#TOC55">9.1 Univariate polynomial rings</A></H2>
<P>CLN implements univariate polynomials (polynomials in one variable) over anarbitrary ring. The indeterminate variable may be either unnamed (and will beprinted according to <CODE>cl_default_print_flags.univpoly_varname</CODE>, whichdefaults to <SAMP>`x'</SAMP>) or carry a given name. The base ring and theindeterminate are explicitly part of every polynomial. CLN doesn't allow you to(accidentally) mix elements of different polynomial rings, e.g.<CODE>(a^2+1) * (b^3-1)</CODE> will result in a runtime error. (Ideally this shouldreturn a multivariate polynomial, but they are not yet implemented in CLN.)
<P>The classes of univariate polynomial rings are
<PRE> Ring cl_ring <cl_ring.h> | | Univariate polynomial ring cl_univpoly_ring <cl_univpoly.h> | +----------------+-------------------+ | | | Complex polynomial ring | Modular integer polynomial ring cl_univpoly_complex_ring | cl_univpoly_modint_ring <cl_univpoly_complex.h> | <cl_univpoly_modint.h> | +----------------+ | | Real polynomial ring | cl_univpoly_real_ring | <cl_univpoly_real.h> | | +----------------+ | | Rational polynomial ring | cl_univpoly_rational_ring | <cl_univpoly_rational.h> | | +----------------+ | Integer polynomial ring cl_univpoly_integer_ring <cl_univpoly_integer.h></PRE>
<P>and the corresponding classes of univariate polynomials are
<PRE> Univariate polynomial cl_UP <cl_univpoly.h> | +----------------+-------------------+ | | | Complex polynomial | Modular integer polynomial cl_UP_N | cl_UP_MI <cl_univpoly_complex.h> | <cl_univpoly_modint.h> | +----------------+ | | Real polynomial | cl_UP_R | <cl_univpoly_real.h> | | +----------------+ | | Rational polynomial | cl_UP_RA | <cl_univpoly_rational.h> | | +----------------+ | Integer polynomial cl_UP_I <cl_univpoly_integer.h></PRE>
<P>Univariate polynomial rings are constructed using the functions
<DL COMPACT>
<DT><CODE>cl_univpoly_ring cl_find_univpoly_ring (const cl_ring& R)</CODE><DD><DT><CODE>cl_univpoly_ring cl_find_univpoly_ring (const cl_ring& R, const cl_symbol& varname)</CODE><DD>This function returns the polynomial ring <SAMP>`R[X]'</SAMP>, unnamed or named.<CODE>R</CODE> may be an arbitrary ring. This function takes care of finding outabout special cases of <CODE>R</CODE>, such as the rings of complex numbers,real numbers, rational numbers, integers, or modular integer rings.There is a cache table of rings, indexed by <CODE>R</CODE> and <CODE>varname</CODE>.This ensures that two calls of this function with the same arguments willreturn the same polynomial ring.
<DT><CODE>cl_univpoly_complex_ring cl_find_univpoly_ring (const cl_complex_ring& R)</CODE><DD><A NAME="IDX271"></A><DT><CODE>cl_univpoly_complex_ring cl_find_univpoly_ring (const cl_complex_ring& R, const cl_symbol& varname)</CODE><DD><DT><CODE>cl_univpoly_real_ring cl_find_univpoly_ring (const cl_real_ring& R)</CODE><DD><DT><CODE>cl_univpoly_real_ring cl_find_univpoly_ring (const cl_real_ring& R, const cl_symbol& varname)</CODE><DD><DT><CODE>cl_univpoly_rational_ring cl_find_univpoly_ring (const cl_rational_ring& R)</CODE><DD><DT><CODE>cl_univpoly_rational_ring cl_find_univpoly_ring (const cl_rational_ring& R, const cl_symbol& varname)</CODE><DD><DT><CODE>cl_univpoly_integer_ring cl_find_univpoly_ring (const cl_integer_ring& R)</CODE><DD><DT><CODE>cl_univpoly_integer_ring cl_find_univpoly_ring (const cl_integer_ring& R, const cl_symbol& varname)</CODE><DD><DT><CODE>cl_univpoly_modint_ring cl_find_univpoly_ring (const cl_modint_ring& R)</CODE><DD><DT><CODE>cl_univpoly_modint_ring cl_find_univpoly_ring (const cl_modint_ring& R, const cl_symbol& varname)</CODE><DD>These functions are equivalent to the general <CODE>cl_find_univpoly_ring</CODE>,only the return type is more specific, according to the base ring's type.</DL>
<H2><A NAME="SEC56" HREF="cln_toc.html#TOC56">9.2 Functions on univariate polynomials</A></H2>
<P>Given a univariate polynomial ring <CODE>R</CODE>, the following members can be used.
<DL COMPACT>
<DT><CODE>cl_ring R->basering()</CODE><DD><A NAME="IDX272"></A>This returns the base ring, as passed to <SAMP>`cl_find_univpoly_ring'</SAMP>.
<DT><CODE>cl_UP R->zero()</CODE><DD><A NAME="IDX273"></A>This returns <CODE>0 in R</CODE>, a polynomial of degree -1.
<DT><CODE>cl_UP R->one()</CODE><DD><A NAME="IDX274"></A>This returns <CODE>1 in R</CODE>, a polynomial of degree <= 0.
<DT><CODE>cl_UP R->canonhom (const cl_I& x)</CODE><DD><A NAME="IDX275"></A>This returns <CODE>x in R</CODE>, a polynomial of degree <= 0.
<DT><CODE>cl_UP R->monomial (const cl_ring_element& x, uintL e)</CODE><DD><A NAME="IDX276"></A>This returns a sparse polynomial: <CODE>x * X^e</CODE>, where <CODE>X</CODE> is theindeterminate.
<DT><CODE>cl_UP R->create (sintL degree)</CODE><DD><A NAME="IDX277"></A>Creates a new polynomial with a given degree. The zero polynomial has degree<CODE>-1</CODE>. After creating the polynomial, you should put in the coefficients,using the <CODE>set_coeff</CODE> member function, and then call the <CODE>finalize</CODE>member function.</DL>
<P>The following are the only destructive operations on univariate polynomials.
<DL COMPACT>
<DT><CODE>void set_coeff (cl_UP& x, uintL index, const cl_ring_element& y)</CODE><DD><A NAME="IDX278"></A>This changes the coefficient of <CODE>X^index</CODE> in <CODE>x</CODE> to be <CODE>y</CODE>.After changing a polynomial and before applying any "normal" operation on it,you should call its <CODE>finalize</CODE> member function.
<DT><CODE>void finalize (cl_UP& x)</CODE><DD><A NAME="IDX279"></A>This function marks the endpoint of destructive modifications of a polynomial.It normalizes the internal representation so that subsequent computations haveless overhead. Doing normal computations on unnormalized polynomials mayproduce wrong results or crash the program.</DL>
<P>The following operations are defined on univariate polynomials.
<DL COMPACT>
<DT><CODE>cl_univpoly_ring x.ring ()</CODE><DD><A NAME="IDX280"></A>Returns the ring to which the univariate polynomial <CODE>x</CODE> belongs.
<DT><CODE>cl_UP operator+ (const cl_UP&, const cl_UP&)</CODE><DD><A NAME="IDX281"></A>Returns the sum of two univariate polynomials.
<DT><CODE>cl_UP operator- (const cl_UP&, const cl_UP&)</CODE><DD><A NAME="IDX282"></A>Returns the difference of two univariate polynomials.
<DT><CODE>cl_UP operator- (const cl_UP&)</CODE><DD>Returns the negative of a univariate polynomial.
<DT><CODE>cl_UP operator* (const cl_UP&, const cl_UP&)</CODE><DD><A NAME="IDX283"></A>Returns the product of two univariate polynomials. One of the arguments mayalso be a plain integer or an element of the base ring.
<DT><CODE>cl_UP square (const cl_UP&)</CODE><DD><A NAME="IDX284"></A>Returns the square of a univariate polynomial.
<DT><CODE>cl_UP expt_pos (const cl_UP& x, const cl_I& y)</CODE><DD><A NAME="IDX285"></A><CODE>y</CODE> must be > 0. Returns <CODE>x^y</CODE>.
<DT><CODE>bool operator== (const cl_UP&, const cl_UP&)</CODE><DD><A NAME="IDX286"></A><DT><CODE>bool operator!= (const cl_UP&, const cl_UP&)</CODE><DD><A NAME="IDX287"></A>Compares two univariate polynomials, belonging to the same univariatepolynomial ring, for equality.
<DT><CODE>cl_boolean zerop (const cl_UP& x)</CODE><DD><A NAME="IDX288"></A>Returns true if <CODE>x</CODE> is <CODE>0 in R</CODE>.
<DT><CODE>sintL degree (const cl_UP& x)</CODE><DD><A NAME="IDX289"></A>Returns the degree of the polynomial. The zero polynomial has degree <CODE>-1</CODE>.
<DT><CODE>cl_ring_element coeff (const cl_UP& x, uintL index)</CODE><DD><A NAME="IDX290"></A>Returns the coefficient of <CODE>X^index</CODE> in the polynomial <CODE>x</CODE>.
<DT><CODE>cl_ring_element x (const cl_ring_element& y)</CODE><DD><A NAME="IDX291"></A>Evaluation: If <CODE>x</CODE> is a polynomial and <CODE>y</CODE> belongs to the base ring,then <SAMP>`x(y)'</SAMP> returns the value of the substitution of <CODE>y</CODE> into<CODE>x</CODE>.
<DT><CODE>cl_UP deriv (const cl_UP& x)</CODE><DD><A NAME="IDX292"></A>Returns the derivative of the polynomial <CODE>x</CODE> with respect to theindeterminate <CODE>X</CODE>.</DL>
<P>The following output functions are defined (see also the chapter oninput/output).
<DL COMPACT>
<DT><CODE>void fprint (cl_ostream stream, const cl_UP& x)</CODE><DD><A NAME="IDX293"></A><DT><CODE>cl_ostream operator<< (cl_ostream stream, const cl_UP& x)</CODE><DD><A NAME="IDX294"></A>Prints the univariate polynomial <CODE>x</CODE> on the <CODE>stream</CODE>. The output maydepend on the global printer settings in the variable<CODE>cl_default_print_flags</CODE>.</DL>
<H2><A NAME="SEC57" HREF="cln_toc.html#TOC57">9.3 Special polynomials</A></H2>
<P>The following functions return special polynomials.
<DL COMPACT>
<DT><CODE>cl_UP_I cl_tschebychev (sintL n)</CODE><DD><A NAME="IDX295"></A><A NAME="IDX296"></A>Returns the n-th Tchebychev polynomial (n >= 0).
<DT><CODE>cl_UP_I cl_hermite (sintL n)</CODE><DD><A NAME="IDX297"></A><A NAME="IDX298"></A>Returns the n-th Hermite polynomial (n >= 0).
<DT><CODE>cl_UP_RA cl_legendre (sintL n)</CODE><DD><A NAME="IDX299"></A><A NAME="IDX300"></A>Returns the n-th Legendre polynomial (n >= 0).
<DT><CODE>cl_UP_I cl_laguerre (sintL n)</CODE><DD><A NAME="IDX301"></A><A NAME="IDX302"></A>Returns the n-th Laguerre polynomial (n >= 0).</DL>
<P>Information how to derive the differential equation satisfied by eachof these polynomials from their definition can be found in the<CODE>doc/polynomial/</CODE> directory.
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