calc/help/poly

NAME
    poly - evaluate a polynomial

SYNOPSIS
    poly(a, b, ..., x)
    poly(clist, x, y, ...)

TYPES
    For first case:

    a, b, ...	Arithmetic

    x		Arithmetic

    return	Depends on argument types

    For second case:

    clist	List of coefficients

    x, y, ...	Coefficients

    return	Depends on argument types

    Here an arithmetic type is one for which the required + and *
    operations are defined, e.g. real or complex numbers or square
    matrices of the same size.	A coefficient is either of arithmetic
    type or a list of coefficients.

DESCRIPTION
    If the first argument is not a list, and the necessary operations are
    defined:

	poly(a_0, a_1, ..., a_n, x)

     returns the value of:

	a_n + (a_n-1 + ... + (a_1 + a_0 * x) * x ...) * x

    If the coefficients a_0, a_1, ..., a_n and x are elements of a
    commutative ring, e.g. if the coefficients and x are real or complex
    numbers, this is the value of the polynomial:

	a_0 * x^n + a_1 * x^(n-1) + ... + a_(n-1) * x + a_n.

    For other structures (e.g. if addition is not commutative),
    the order of operations may be relevant.

    In particular:

	poly(a, x) returns the value of a.

	poly(a, b, x) returns the value of b + a * x

	poly(a, b, c, x) returns the value of c + (b + a * x) * x


    If the first argument is a list as if defined by:

	clist = list(a_0, a_1, ..., a_n)

    and the coefficients a_i and x are are of arithmetic type,
    poly(clist, x) returns:

	a_0 + (a_1 + (a_2 + ... + a_n * x) * x)

    which for a commutative ring, expands to:

	a_0 + a_1 * x + ... + a_n * x^n.

    If clist is the empty list, the value returned is the number 0.

    Note that the order of the coefficients for the list case is the
    reverse of that for the non-list case.

    If one or more elements of clist is a list and there are more than
    one arithmetic arguments x, y, ..., the coefficient corresponding
    to such an element is the value of poly for that list and the next
    argument in x, y, ...  For example:

	poly(list(list(a,b,c), list(d,e), f), x, y)

    returns:

	 (a + b * y + c * y^2) + (d + e * y) * x + f * x^2.

    Arguments in excess of those required for clist are ignored, e.g.:

	poly(list(1,2,3), x, y)

    returns the same as poly(list(1,2,3), x).  If the number of
    arguments is less than greatest depth of lists in clist, the
    "missing" arguments are deemed to be zero.	E.g.:

	poly(list(list(1,2), list(3,4), 5), x)

    returns the same as:

	poly(list(1, 3, 5), x).

    If in the clist case, one or more of x, y, ... is a list, the
    arguments to be applied to the polynomial are the successive
    non-list values in the list or sublists.  For example, if the x_i
    are not lists:

	poly(clist, list(x_0, x_1), x_2, list(list(x_3, x_4), x_5))

    returns the same as:

	poly(clist, x_0, x_1, x_2, x_3, x_4, x_5).

EXAMPLE
    > print poly(2, 3, 5, 7), poly(list(5, 3, 2), 7), 5 + 3 * 7 + 2 * 7^2
    124 124 124

    > mat A[2,2] = {1,2,3,4}
    > mat I[2,2] = {1,0,0,1}
    print poly(2 * I, 3 * I, 5 * I, A)

    mat [2,2] (4 elements, 4 nonzero)
      [0,0] = 22
      [0,1] = 26
      [1,0] = 39
      [1,1] = 61

    > P = list(list(0,0,1), list(0,2), 3); x = 4; y = 5
    > print poly(P,x,y), poly(P, list(x,y)), y^2 + 2 * y * x + 3 * x^2
    113 113 113

LIMITS
    The number of arguments is not to exceed 100

LINK LIBRARY
    BOOL evalpoly(LIST *clist, LISTELEM *x, VALUE *result);

SEE ALSO
    XXX - fill in

## Copyright (C) 1999  Landon Curt Noll
##
## Calc is open software; you can redistribute it and/or modify it under
## the terms of the version 2.1 of the GNU Lesser General Public License
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## 59 Temple Place, Suite 330, Boston, MA  02111-1307, USA.
##
## @(#) $Revision: 29.1 $
## @(#) $Id: poly,v 29.1 1999/12/14 09:16:02 chongo Exp $
## @(#) $Source: /usr/local/src/cmd/calc/help/RCS/poly,v $
##
## Under source code control:	1995/12/02 02:40:43
## File existed as early as:	1995
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## chongo <was here> /\oo/\	http://reality.sgi.com/chongo/
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