// Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
// Copyright (C) INRIA - 1989 - C. Bunks
// Copyright (C) INRIA - 1997 - C. Bunks
//
// This file must be used under the terms of the CeCILL.
// This source file is licensed as described in the file COPYING, which
// you should have received as part of this distribution.  The terms
// are also available at
// http://www.cecill.info/licences/Licence_CeCILL_V2.1-en.txt

function [npl,nzr,ngn]=bilt(pl,zr,gn,num,den)
    //[npl,nzr,ngn]=bilt(pl,zr,gn,num,den)
    //macro for calculating the gain poles and zeros
    //which result from a bilinear transform or from
    //a biquadratic transform.  Used by the macros iir
    //and trans
    //Note: ***This macro is not intended for general use***
    //  pl  :input poles
    //  zr  :input zeros
    //  gn  :input gain
    //  num :numerator of transform
    //  den :denominator of transform
    //!
    if type(pl)<>1 then
        error(msprintf(gettext("%s: Wrong type for input argument #%d: Array of floating point numbers expected.\n") ,"bilt",1))
    end
    if type(zr)<>1 then
        error(msprintf(gettext("%s: Wrong type for input argument #%d: Array of floating point numbers expected.\n") ,"bilt",2))
    end
    if type(gn)<>1 then
        error(msprintf(gettext("%s: Wrong type for input argument #%d: Array of floating point numbers expected.\n") ,"bilt",3))
    end
    if size(gn,"*")<>1 then
        error(msprintf(gettext("%s: Wrong size for input argument #%d: A scalar expected.\n") ,"bilt",3))
    end
    if type(num)<>2|size(num,"*")<>1 then
        error(msprintf(gettext("%s: Wrong size for input argument #%d: A polynomial expected.\n") ,"bilt",4))
    end
    if type(den)<>2|size(den,"*")<>1 then
        error(msprintf(gettext("%s: Wrong size for input argument #%d: A polynomial expected.\n") ,"bilt",5))
    end

    order=degree(den)

    if and(order<>[1 2]) then
        error(msprintf(gettext("%s: Wrong values for input argument #%d: degree must be in the set {%s}.\n"),"bilt",5,"1,2"))
    end
    if degree(num)<>order then
        error(msprintf(gettext("%s: Incompatible input arguments #%d and #%d: Same degree expected.\n"),"bilt",4,5))
    end
    n=coeff(num);
    d=coeff(den);
    ms=max(size(pl));ns=max(size(zr));

    select order
    case 1  then
        n0=n(1);n1=n(2);
        d0=d(1);d1=d(2);
        if zr == [] then
            ngn=1/prod(n1*ones(pl)-d1*pl);
        else
            ngn=prod(n1*ones(zr)-d1*zr)/prod(n1*ones(pl)-d1*pl);
        end
        if ms<>ns then ngn=real(gn*d1**(ms-ns)*ngn);else ngn=real(gn*ngn);end
        nzr=-(n0*ones(zr)-d0*zr)./(n1*ones(zr)-d1*zr);
        npl=-(n0*ones(pl)-d0*pl)./(n1*ones(pl)-d1*pl);
        if ms>ns then
            nzr=[nzr';-(d0/d1)*ones(ms-ns,1)];
        elseif ms<ns then
            npl=[npl';-(d0/d1)*ones(ms-ns,1)];
        end
    case 2 then
        n0=n(1);n1=n(2);n2=n(3);
        d0=d(1);d1=d(2);d2=d(3);
        a=n2*ones(zr)-d2*zr;
        b=n1*ones(zr)-d1*zr;
        c=n0*ones(zr)-d0*zr;
        gz=a;
        z1=-b./(2*a)+sqrt((b./(2*a)).^2-c./a);
        z2=-b./(2*a)-sqrt((b./(2*a)).^2-c./a);
        a=n2*ones(pl)-d2*pl;
        b=n1*ones(pl)-d1*pl;
        c=n0*ones(pl)-d0*pl;
        gp=a;
        p1=-b./(2*a)+sqrt((b./(2*a)).^2-c./a);
        p2=-b./(2*a)-sqrt((b./(2*a)).^2-c./a);
        gw=d2;
        w1=-d1./(2*d2)+sqrt((d1./(2*d2))**2-d0./d2);
        w2=-d1./(2*d2)-sqrt((d1./(2*d2))**2-d0./d2);
        ngn=gn*prod(gz)/prod(gp);
        nzr=[z1,z2];
        npl=[p1,p2];
        if ms>ns then
            nzr=[nzr';-(d0/d1)*ones(ms-ns,1)];
        elseif ms<ns then
            npl=[npl';-(d0/d1)*ones(ms-ns,1)];
        end
        ngn=real(ngn*(gw**(ms-ns)));
    end
endfunction