module vdp2dip;

imports dipoly;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% interface for Virtual Distributive Polynomials (VDP)
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
% "Distributive representation" with respect to  a given set of
% variables  ("vdpvars") means for a polynomial, that the polynomial
% is regarded as  a sequence of monomials, each of which is a
% product of a "coefficient"  and of some powers of the variables.
% This internal representation is  very closely connected to the
% standard external (printed) representation of a  polynomial in
% REDUCE if nothing is factored out. The monomials are logically
% ordered by a term order mode based on the  ordering which is
% given bye the sequence "vdpvars"; with respect to this  ordering
% the representation of a polynomial is unique. The "highest" term
%  is the car one. Monomials are represented by their coefficient
% ("vbc") and by  a vector of the exponents("vev") (in the order 
% corresponding to the  vector vars). The distributive representation
% is good for those algorithms, which  base their decisions on the
% complete ledading monomial:  this representation guarantees a 
% fast and uniform access to the car monomial and to the reductum
% (the cdr of the polynomial beginning with the cadr monomial).
% The algorithms of the Groebner package are of this type.  The 
% interface defines the distributive polynomials as abstract data
% objects via their acess functions. These functions map the
% distributive operations to an arbitrary real data structure
% ("virtual"). The mapping of the access functions to an actual
% data structure is cdrricted only by the demand, that the typical
% "distributive operations" be efficient.  Additionally to the
% algebraic value a VDP object has a property list. So the algorithms
% using the  VDP interface can assign name-value-pairs to individual
% polynomials. The interface is defined by a set of routines which
% create and handle the distributive polynomials. In general the
% first letters of the routine name classifies the data its works on:
 
%   vdp...      complete virt. polynomial objects
%   vbc...      virt. base coefficients
%   vev...      virt. exponent vectors
 
% 0. general control
%
%   vdpinit(dv) initialises the vdp package for the variables
%              given in the list "dv". vdpinit modifies the
%              torder and returns the prvevious torder as its
%              result. vdpinit sets the global variable
%              vdpvars!*;
 
% 1. conversion
%
%   a2vdp      algebraic (prefix) to vdp
%   f2vdp      standard form to vdp
%   a2vbc      algebraic (prefix) to vbc
%   vdp2a      vdp to algebraic (prefix)
%   vdp2f      vdp to standard form
%   vbc2a      vbc to algebraic (prefix)
 
% 2. composing/decomposing
%
%   vdpfmon    make a vdp from a vbc and an vev
%   vdpMonComp add a monomial (vbc and vev) to the front of a vdp
%   vdpAppendMon add a monomial (vbc and vev) to the bottom of a vdp
%   vdpMonAdd  add a monomial (vbc and vev) to a vdp, not yet 
%              knowing the place of the insertion
%   vdpAppendVdp concat two vdps
%
%   vdpLbc     extract leading vbc
%   vdpevlmon  extract leading vev
%   vdpred     reductum of vdp
%   vdplastmon last monomial of polynomial
%   vevnth      nth element from exponent vector
 
% 3. testing
%
%   vdpZero?    test vdp = 0
%   vdpredZero!? test rductum of vdp = 0
%   vdpOne?     test vdp = 1
%   vevZero?    test vev = (0 0 ... 0)
%   vbczero?    test vbc = 0
%   vbcminus?   test vbc <= 0 (not decidable for algebraic vbcs)
%   vbcplus?    test vbc >= 0 (not decidable for algebraic vbcs)
%   vbcone!?    test vbc = 1
%   vbcnumberp  test vbc is a numeric value
%   vevdivides? test if vev1 < vev2 elementwise
%   vevlcompless?  test ordering vev1 < vev2
%   vdpvevlcomp    calculate ordering vev1 / vev1: -1, 0 or +1
%   vdpEqual   test vdp1 = vdp2
%   vdpMember  member based on "vdpEqual"
%   vevequal    test vev1 = vev2
 
% 4. arithmetic
%
% 4.1 vdp arithmetic
%
%  vdpsum       vdp + vdp
%               special routines for monomials: see above (2.)
%  vdpdif       vdp - vdp
%  vdpprod      vdp * vdp
%  vdpvbcprod   vbc * vdp
%  vdpDivMon    vdp / (vbc,vev)  divisability presumed
%  vdpCancelvev substitute all multiples of monomial (1,vev) in vdp by 0
%  vdpLcomb1    vdp1*(vbc1,vev1) + vdp2*(vbc2,vev2)
%  vdpContent   calculate gcd over all vbcs
 
% 4.2 vbc arithmetic
%
%  vbcsum       vbc1 + vbc2
%  vbcdif       vbc1 - vbc2
%  vbcneg       - vbc
%  vbcprod      vbc1 * vbc2
%  vbcquot      vbc1 / vbc2     divisability assumed if domain = ring
%  vbcinv       1 / vbc        only usable in field
%  vbcgcd       gcd(vbc1,vbc2)  only usable in Euclidean field
 
% 4.2 vev arithmetic
%
% vevsum        vev1 + vev2 elementwise
% vevdif        vev1 - vev2 elementwise
% vevtdeg       sum over all exponents
% vevzero       generate a zero vev
 
% 5. auxiliary
%
% vdpPutProp   assign indicator-value-pair to vdp
%              the property "number" is used for printing.
% vdpGetProp   read value of indicator from vdp
% vdplSort     sort list of polynomials with respect to ordering
% vdplSortIn   sort a vdp into a sorted list of vdps
% vdpprint     print a vdp together with its number
% vdpprin2t    print a vdp "naked"
% vdpprin3t    print a vdp with closing ";"
% vdpcondense  replace exponent vectors by equal objects from
%              global list dipevlist!* in order to save memory 

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% RECORD STRUCTURE
%
% a virtual polynomial here is a record (list) with the entries
%    ('vdp <vdpevlmon> <vdplbc> <form> <plist>)
%
%     'vdp        a type tag
%     <vdpevlmon> the exponents of the variables in the leading
%                 leading monomial; the positions correspond to
%                 the positions in vdpvars!*. Trailing zeroes
%                 can be omitted.
%
%     <lcoeff>    the "coefficient" of the leading monomial, which
%                 in general is a standard form.
%
%     <form>      the complete polynomial, e.g. as REDUCE standard form.
%
%     <plist>     an asso list for the properties of the polynomial
%
% The components should not be manipulated only via the interface
% functions and macros, so that application programs remain
% independent from the internal representation.
% The only general assumption made on <form> is, that the zero
% polynomial is represented as NIL. That is the case e.g. for both,
% REDUCE standard forms and DIPOLYs.
 
% Conventions for the usage:
% -------------------------
%
%    vdpint has to be called prveviously to all vdp calls. The list of
%    vdp paraemters is passed to vdpinit. The value of vdpvars!*
%    and the current torder must remain unmodfied afterwards.
%    usual are simple id's, e.g.
%
%
% Modifications to vdpvars!* during calculations
% ----------------------------------------------
%
% This mapping of vdp operations to standard forms offers the
% ability to enlarge vdpvars during the calculation in order
% to add new (intermediate) variables. Basis is the convention,
% that exponent vectors logically have an arbitrary number
% of trailing zeros. All routines processing exponent vectors
% are able to handle varying length of exponent vectors.
% A new call to vdpinit is necessary.
%
% During calculation vdpvars may be enlarged (new variables
% suffixed) without needs to modify existing polynomials; only
% korder has to be set to the new variable sequence.
% modifications to the sequence in vdpvars requires a
% new call to vdpinit  and a reordering of exisiting
% polynomials, e.g. by
%          vdpint newvdpvars;
%          f2vdp vdp2f p1; f2vdp vdp2f p2; .....
 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% DECLARATION SECTION
%
%  this module must be present during code generation for modules
%  using the vdp - sf interface

fluid '(vdpvars!* intvdpvars!* secondvalue!* vdpsortmode!* !*groebrm
        !*vdpinteger !*trgroeb !*trgroebs !*groebdivide pcount!*
        !*gsugar dipevlist!* !*gcd);
 
global '(vdpprintmax groebmonfac);
 
flag('(vdpprintmax),'share);
 
% basic internal constructor of vdp-record
smacro procedure makevdp (vbc,vev,form); list('vdp,vev,vbc,form,nil);

% basic selectors (conversions)
 
smacro procedure vdppoly u; cadr cddr u;

smacro procedure vdplbc u; caddr u;
 
smacro procedure vdpevlmon u; cadr u;
 
% basic tests
 
smacro procedure vdpzero!? u;
    null u or null vdppoly u;
 
smacro procedure vevzero!? u;
    null u or (car u = 0 and vevzero!?1 cdr u);

smacro procedure vdpone!? p;
     not vdpzero!? p and vevzero!? vdpevlmon p;

% base coefficients
 
%  manipulating of exponent vectors
 
smacro procedure vevdivides!? (vev1,vev2);
        vevmtest!?(vev2,vev1);

smacro procedure vevzero();
        vevmaptozero1(vdpvars!*,nil);
 
smacro procedure vdpnumber f; vdpgetprop(f,'number) ;
 
% the code for checkpointing is factored out
% This version: NO CHECKPOINT FACILITY
 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% interface for DIPOLY polynomials as records (objects).
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
 
fluid '(intvdpvars!* vdpvars!* secondvalue!* vdpsfsortmode!* !*groebrm
        !*vdpinteger !*trgroeb !*trgroebs !*groebdivide pcount!*
        !*groebsubs);
 
fluid '(vdpsortmode!*);
 
global '(vdpprintmax groebmonfac);
flag('(vdpprintmax),'share);
 
fluid '(dipvars!* !*vdpinteger);
 
symbolic procedure dip2vdp u;
 % Is used when u can be empty.
   (if dipzero!? uu then makevdp(a2bc 0,nil,nil)
                    else makevdp(diplbc uu,dipevlmon uu,uu))
           where uu = if !*groebsubs then dipsubs2 u else u;

% some simple mappings
 
smacro procedure makedipzero(); nil;
 
symbolic procedure vdpredzero!? u; dipzero!? dipmred vdppoly u;

symbolic procedure vdplastmon u;
 % Return bc . ev of last monomial of u.
  begin
    u:=vdppoly u; 
    if dipzero!? u then return nil;
    while not dipzero!? u and not dipzero!? dipmred u do
        u:=dipmred u;
    return diplbc u . dipevlmon u;
  end;
 
symbolic procedure vbczero!? u; bczero!? u;
 
symbolic procedure vbcnumber u; 
       if  pairp u and numberp car u and 1=cdr u then cdr u else nil;

symbolic procedure vbcfi u; bcfd u;
 
symbolic procedure a2vbc u; a2bc u;
 
symbolic procedure vbcquot(u,v); bcquot(u,v);
 
symbolic procedure vbcneg u; bcneg u;
 
symbolic procedure vbcabs u; if vbcminus!? u then bcneg u else u; 
 
symbolic procedure vbcone!? u; bcone!? u; 
 
symbolic procedure vbcprod (u,v); bcprod(u,v);
 
 % initializing vdp-dip polynomial package
symbolic procedure vdpinit2(vars);
  begin scalar oldorder;
    vdpcleanup();
    oldorder := kord!*;
    if null vars then rerror(dipoly,8,"Vdpinit: vdpvars not set");
    vdpvars!* := dipvars!* := vars;
    torder2 vdpsortmode!*;
    return oldorder;
  end;
 
symbolic procedure vdpcleanup();
   dipevlist!*:={nil};
     
symbolic procedure vdpred u;
   begin scalar r,s;
     r:=dipmred vdppoly u;
     if dipzero!? r then return makevdp(nil ./ nil,nil,makedipzero());
     r:=makevdp(diplbc r,dipevlmon r,r);
     if !*gsugar and (s:=vdpgetprop(u,'sugar)) then gsetsugar(r,s);
     return r;
  end;
 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  coefficient handling; here we assume that coefficients are
%  standard quotients;
%
 
symbolic procedure vbcgcd (u,v);
begin scalar x;
     if not vbcsize(u, -100) or not vbcsize(v, -100)
        then return '(1 . 1);
     x := if denr u = 1 and denr v = 1 then
       if fixp numr u and fixp numr v then gcdn(numr u,numr v)  ./ 1
            else gcdf!*(numr u,numr v) ./ 1
     else 1 ./ 1;
      return x
end;

symbolic procedure vbcsize(u, n);
    if n #> -1 then nil
    else if atom u then n
    else 
     begin 
         n := vbcsize(car u, n #+ 1);
         if null n then return nil;
         return vbcsize(cdr u, n);
     end;

% Cofactors: compute (q,v) such that q*a=v*b.

symbolic procedure vbc!-cofac(bc1,bc2);
  % Compute base coefficient cofactors.
  <<if vbcminus!? bc1 and vbcminus!? bc2 then gcd:=vbcneg gcd;
    vbcquot(bc2,gcd).vbcquot(bc1,gcd) >>
      where gcd=vbcgcd(bc1,bc2);
  
symbolic procedure vev!-cofac(ev1,ev2);
  % Compute exponent vector cofactors.
  (vevdif(lcm,ev1) . vevdif(lcm,ev2)) where lcm =vevlcm(ev1,ev2);
 
% the following functions must be redefinable
symbolic procedure vbcplus!? u; (numberp v and v>0) where v = numr u;
symbolic procedure bcplus!? u; (numberp v and v>0) where v = numr u;
 
symbolic procedure vbcminus!? u; 
       (numberp v and v<0) where v = numr u;
 
symbolic procedure vbcinv u; bcinv u;
 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  conversion between forms, vdps and prefix expressions
%
 
% prefix to vdp
symbolic procedure a2vdp u;
     if u=0 or null u then makevdp(nil ./ nil,nil,makedipzero())
     else (makevdp(diplbc r,dipevlmon r,r)  where  r = a2dip u);
 
% vdp to prefix
symbolic procedure vdp2a u; dip2a vdppoly u;
 
symbolic procedure vbc2a u; bc2a  u;
 
% form to vdp
symbolic procedure f2vdp(u);
     if u=0 or null u then makevdp(nil ./ nil,nil,makedipzero())
     else (makevdp(diplbc r,dipevlmon r,r)  where  r = f2dip u);
 
% vdp to form
symbolic procedure vdp2f u; dip2f vdppoly u;
 
% vdp from monomial
symbolic procedure vdpfmon (coef,vev); 
   begin scalar r;
    r:= makevdp(coef,vev,dipfmon(coef,vev));
    if !*gsugar then gsetsugar(r,vevtdeg vev);
    return r;
  end;
 
% add a monomial to a vdp in front (new vev and coeff)
symbolic procedure vdpmoncomp(coef,vev,vdp);
   if vdpzero!? vdp then vdpfmon(coef,vev)
         else
   if vbczero!? coef then vdp
         else
   makevdp(coef,vev,dipmoncomp(coef,vev,vdppoly vdp));
 
%add a monomial to the end of a vdp (vev remains unchanged)
symbolic procedure vdpappendmon(vdp,coef,vev);
   if vdpzero!? vdp then vdpfmon(coef,vev)
         else
   if vbczero!? coef then vdp
         else
   makevdp(vdplbc vdp,vdpevlmon vdp,
            dipsum(vdppoly vdp,dipfmon(coef,vev)));
 
% add monomial to vdp, place of new monomial still unknown
symbolic procedure vdpmonadd(coef,vev,vdp);
    if vdpzero!? vdp then vdpfmon(coef,vev) else
   (if c = 1 then vdpmoncomp(coef,vev,vdp) else
    if c = -1 then makevdp (vdplbc vdp,vdpevlmon vdp,
                               dipsum(vdppoly vdp,dipfmon(coef,vev)))
    else vdpsum(vdp,vdpfmon(coef,vev))
   ) where c = vevcomp(vev,vdpevlmon vdp);
 
symbolic procedure vdpzero(); a2vdp 0;
 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  comparing of exponent vectors
%
%
 
symbolic procedure vdpvevlcomp (p1,p2); 
                  dipevlcomp (vdppoly p1,vdppoly p2);
symbolic procedure vevilcompless!?(e1,e2); 1 = evilcomp(e2,e1);
symbolic procedure vevilcomp (e1,e2); evilcomp (e1,e2);
symbolic procedure vevcompless!?(e1,e2); 1 = evcomp(e2,e1);
symbolic procedure vevcomp (e1,e2); evcomp (e1,e2);
 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  routines traversing the "coefficients"
%
 
% CONTENT of a vdp
% The content is the gcd of all coefficients.
 
symbolic procedure vdpcontent d; 
     if vdpzero!? d then a2bc 0 else
     <<d := vdppoly d;
       dipnumcontent(dipmred d,diplbc d)>>;
 
symbolic procedure vdpcontent1(d,c); dipnumcontent(vdppoly d,c);
 
symbolic procedure dipnumcontent(d,c);
     if bcone!? c or dipzero!? d then c
     else dipnumcontent(dipmred d,vbcgcd(c,diplbc d));
 
symbolic procedure dipcontenti p;
% the content is a pair of the lcm of the coefficients and the
% exponent list of the common monomial factor.
   if dipzero!? p then 1 else
   (if dipzero!? rp then diplbc p .
                             (if !*groebrm then dipevlmon p else nil)
      else
    dipcontenti1(diplbc p,
                 if !*groebrm then dipevlmon p else nil,rp) )
                           where rp=dipmred p;
 
symbolic procedure dipcontenti1 (n,ev,p1);
   if dipzero!? p1 then n . ev
   else begin scalar nn;
             nn := vbcgcd (n,diplbc p1);
             if ev then ev := dipcontevmin(dipevlmon p1,ev);
             if bcone!? nn and null ev then return nn . nil
                       else return dipcontenti1 (nn,ev,dipmred p1)
       end;
 
% CONTENT and MONFAC (if groebrm on)
symbolic procedure vdpcontenti d;
       vdpcontent d . if !*groebrm then vdpmonfac d else nil;
 
symbolic procedure vdpmonfac d; dipmonfac vdppoly d;

symbolic procedure dipmonfac p;
% exponent list of the common monomial factor.
   if dipzero!? p or not !*groebrm then evzero()  
   else (if dipzero!? rp then dipevlmon p
         else dipmonfac1(dipevlmon p,rp) ) where rp=dipmred p;

symbolic procedure dipmonfac1(ev,p1);
   if dipzero!? p1 or evzero!? ev then ev
   else dipmonfac1(dipcontevmin(ev,dipevlmon p1),dipmred p1);

% vdpCoeffcientsFromDomain!?
symbolic procedure vdpcoeffcientsfromdomain!? w;
          dipcoeffcientsfromdomain!? vdppoly w;
 
symbolic procedure dipcoeffcientsfromdomain!? w;
      if dipzero!? w then t else
     (if bcdomain!? v then dipcoeffcientsfromdomain!? dipmred w
       else nil) where v =diplbc w;

symbolic procedure vdplength f; diplength vdppoly f;
 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  polynomial operations:
%             coefficient normalization and reduction of monomial
%             factors
%
 
symbolic procedure vdpequal(p1,p2);
     p1 eq p2
     or (n1 and n1 = n2   % number comparison is faster most times
     or dipequal(vdppoly p1,vdppoly p2)
           where n1 = vdpgetprop(p1,'number),
                 n2 = vdpgetprop(p2,'number));

symbolic procedure dipequal(p1,p2);
    if dipzero!? p1 then dipzero!? p2
    else if dipzero!? p2 then nil
    else diplbc p1 = diplbc p2 
     and evequal(dipevlmon p1,dipevlmon p2)
     and dipequal(dipmred p1,dipmred p2);

symbolic procedure evequal(e1,e2);
   % test equality with variable length exponent vectors
     if null e1 and null e2 then t
     else if null e1 then evequal('(0),e2) 
     else if null e2 then evequal(e1,'(0))
     else 0=(car e1 #- car e2) and evequal(cdr e1,cdr e2);

symbolic procedure vdplcm p; diplcm vdppoly p;
 
symbolic procedure vdprectoint(p,q); dip2vdp diprectoint(vdppoly p,q);
 
symbolic procedure vdpsimpcont(p);
          begin scalar r,q;
              q := vdppoly p;
              if dipzero!? q then return p;
              r := dipsimpcont q;
              p := dip2vdp cdr r;  % the polynomial
              r := car r;          % the monomial factor if any
              if not evzero!? r and (dipmred q or evtdeg r>1)
                then vdpputprop(p,'monfac,r);
              return p;
          end;
 
symbolic procedure dipsimpcont  (p);
    if !*vdpinteger or not !*groebdivide  then dipsimpconti p
                          else dipsimpcontr p;
 
% routines for integer coefficient case:
% calculation of contents and dividing all coefficients by it
 
symbolic procedure dipsimpconti (p);
%   calculate the contents of p and divide all coefficients by it
  begin scalar co,lco,res,num;
    if dipzero!?  p then return nil . p;
    co := bcfd 1;
    co := if !*groebdivide then dipcontenti p
             else if !*groebrm then co . dipmonfac p
             else co . nil;
    num := car co;
    if not bcplus!? num then num := bcneg num;
    if not bcplus!? diplbc p then num := bcneg num;
    if bcone!? num  and cdr co = nil  then return nil . p;
    lco := cdr co;
    if groebmonfac neq 0  then lco := dipcontlowerev cdr co;
    res := p;
    if not(bcone!? num and lco = nil) then
                 res := dipreduceconti (p,num,lco);
    if null cdr co then return nil . res;  
    lco := evdif(cdr co,lco);                
    return(if lco and not evzero!? evdif(dipevlmon res,lco)
                           then lco else nil).res;
    end;
 
symbolic procedure vdpreduceconti (p,co,vev);
%  divide polynomial p by monomial from co and vev
        vdpdivmon(p,co,vev);

%  divide all coefficients of p by cont
symbolic procedure dipreduceconti (p,co,ev);
    if dipzero!? p
         then makedipzero()
         else
           dipmoncomp ( bcquot (diplbc p,co),
                        if ev then evdif(dipevlmon p,ev)
                              else dipevlmon p,
                        dipreduceconti (dipmred p,co,ev));
 
% routines for rational coefficient case:
% calculation of contents and dividing all coefficients by it
 
symbolic procedure dipsimpcontr (p);
%   calculate the contents of p and divide all coefficients by it
  begin scalar co,lco,res;
    if dipzero!?  p then return nil . p;
    co := dipcontentr p;
    if bcone!? diplbc p  and co = nil  then return nil . p;
    lco := dipcontlowerev co;
    res := p;
    if not(bcone!? diplbc p and lco = nil) then
               res := dipreducecontr (p,bcinv diplbc p,lco);
    return (if co then evdif(co,lco) else nil) . res;
    end;
 
symbolic procedure dipcontentr p;
% the content is the exponent list of the common monomial factor.
   (if dipzero!? rp then
                            (if !*groebrm then dipevlmon p else nil)
      else
    dipcontentr1(if !*groebrm then dipevlmon p else nil,rp) )
                          where rp=dipmred p;
 
symbolic procedure dipcontentr1 (ev,p1);
   if dipzero!? p1 then ev
      else begin
             if ev then ev := dipcontevmin(dipevlmon p1,ev);
             if null ev then return nil
                       else return dipcontentr1 (ev,dipmred p1)
       end;
 
%  divide all coefficients of p by cont
symbolic procedure dipreducecontr (p,co,ev);
    if dipzero!? p
         then makedipzero()
         else
           dipmoncomp ( bcprod (diplbc p,co),
                        if ev then evdif(dipevlmon p,ev)
                              else dipevlmon p,
                        dipreducecontr (dipmred p,co,ev));
 
symbolic procedure dipcontevmin (e1,e2);
% calculates the minimum of two exponents; if one is shorter, trailing
% zeroes are assumed.
% e1 is an exponent vector. e2 is a list of exponents
    begin scalar res;
       while e1 and e2 do
          <<res := (if ilessp(car e1,car e2) then car e1 else car e2)
                    . res;
            e1 := cdr e1; e2 := cdr e2>>;
       while res and 0=car res do res := cdr res; 
       return reversip res;
    end;
 
symbolic procedure dipcontlowerev (e1);
% subtract a 1 from those elements of an exponent vector which 
% are greater  than 1.
% e1 is a list of exponents, the result is an exponent vector.
    begin scalar res;
       while e1 do
          <<res := (if igreaterp(car e1,0) then car e1 - 1 else 0) 
                    . res;
            e1 := cdr e1>>;
       while res and 0 = car res do res := cdr res;
            if res and !*trgroebs then
                   <<prin2 "***** exponent reduction:"; 
                     prin2t reverse res>>;
       return  reversip res;
    end;
 
symbolic procedure dipappendmon(dip,bc,ev);
         append(dip,dipfmon(bc,ev));
 
smacro procedure dipnconcmon(dip,bc,ev);
         nconc(dip,dipfmon(bc,ev));
 
smacro procedure dipappenddip(dip1,dip2); append(dip1,dip2);
 
smacro procedure dipnconcdip(dip1,dip2); nconc(dip1,dip2);
 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  basic polynomial arithmetic:
%
 
symbolic procedure vdpsum(d1,d2);
   begin scalar r;
     r:=dip2vdp dipsum(vdppoly d1,vdppoly d2);
     if !*gsugar then gsetsugar(r,max(gsugar d1,gsugar d2));
     return r;
   end;
 
symbolic procedure vdpdif(d1,d2);
   begin scalar r;
     r:= dip2vdp dipdif(vdppoly d1,vdppoly d2);
     if !*gsugar then gsetsugar(r,max(gsugar d1,gsugar d2));
     return r;
   end;
 
symbolic procedure vdpprod(d1,d2);
   begin scalar r;
     r:= dip2vdp dipprod(vdppoly d1,vdppoly d2);
     if !*gsugar then gsetsugar(r,gsugar d1 + gsugar d2);
     return r;
   end;
 
% % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % %
%
%  linear combination: the Buchberger Workhorse
%
% LCOMB1: calculate mon1 * vdp1 + mon2 * vdp2
symbolic procedure vdpilcomb1(d1,vbc1,vev1,d2,vbc2,vev2);
 begin scalar r;
  r:=
 dip2vdp dipilcomb1 (vdppoly d1,vbc1,vev1,vdppoly d2,vbc2,vev2);
  if !*gsugar then gsetsugar(r,max(gsugar d1+vevtdeg vev1,
                                   gsugar d2+vevtdeg vev2));
  return r;
 end;
 
symbolic procedure dipilcomb1 (p1,bc1,ev1,p2,bc2,ev2);
% same asl dipILcomb, exponent vectors multiplied in already
begin scalar gcd;
   gcd := !*gcd;
return
   begin scalar ep1,ep2,sl,res,sum,z1,z2,p1new,p2new,lptr,bptr,c,!*gcd;
       !*gcd := if vbcsize(bc1,-100) and vbcsize(bc2,-100)then gcd;
       z1 := not evzero!? ev1; z2 := not evzero!? ev2;
       p1new := p2new := t;
       lptr := bptr := res := makedipzero();
 loop:
       if p1new then
       << if dipzero!? p1 then
              return if dipzero!? p2 then res else
                     dipnconcdip(res, dipprod(p2,dipfmon(bc2,ev2)));
          ep1 := dipevlmon p1;
          if z1 then ep1 := evsum(ep1,ev1);
          p1new := nil;>>;
       if p2new then
       << if dipzero!? p2 then
              return dipnconcdip(res, dipprod(p1,dipfmon(bc1,ev1)));
          ep2 := dipevlmon p2;
          if z2 then ep2 := evsum(ep2,ev2);
          p2new := nil; >>;
        sl := evcomp(ep1, ep2);
        if sl = 1 then
                << if !*gcd and not vbcsize(diplbc p1, -100)
                             then !*gcd := nil;
                   c := bcprod(diplbc p1,bc1);
                   if not bczero!? c then 
		   <<lptr := dipnconcmon (bptr,c,ep1);
		     bptr := dipmred lptr>>;
                   p1 := dipmred p1; p1new := t;
                >>
        else if sl = -1 then
                << if !*gcd and not vbcsize(diplbc p2, -100)
                              then !*gcd := nil;
                   c := bcprod(diplbc p2,bc2);
                   if not bczero!? c then 
		   <<lptr := dipnconcmon (bptr,c,ep2);
		     bptr := dipmred lptr>>;
                   p2 := dipmred p2; p2new := t;
                >>
        else
                << if !*gcd and (not vbcsize(diplbc p1,-100) or
                      not vbcsize(diplbc p2,-100)) then !*gcd := nil;
                   sum := bcsum (bcprod(diplbc p1,bc1),
                                 bcprod(diplbc p2,bc2));
                   if not bczero!? sum then
                       <<   lptr := dipnconcmon(bptr,sum,ep1);
                            bptr := dipmred lptr>>;
                   p1 := dipmred p1; p2 := dipmred p2;
                   p1new := p2new := t;
                >>;
        if dipzero!? res then <<res := bptr := lptr>>; % initial
        goto loop;
 end;
end;
 
symbolic procedure vdpvbcprod(p,a); 
   (if !*gsugar then gsetsugar(q,gsugar p) else q)
       where q=dip2vdp dipbcprod(vdppoly p,a);
 
symbolic procedure vdpdivmon(p,c,vev);
   (if !*gsugar then gsetsugar(q,gsugar p) else q)
       where q=dip2vdp dipdivmon(vdppoly p,c,vev);

symbolic procedure dipdivmon(p,bc,ev);
    % divides a polynomial by a monomial
    % we are sure that the monomial ev is a factor of p
    if dipzero!? p
         then makedipzero()
         else
           dipmoncomp ( bcquot(diplbc p,bc),
                        evdif(dipevlmon p,ev),
                        dipdivmon (dipmred p,bc,ev));
 
symbolic procedure vdpcancelmvev(p,vev);
    (if !*gsugar then gsetsugar(q,gsugar p) else q)
       where q=dip2vdp dipcancelmev(vdppoly p,vev);
 
symbolic procedure dipcancelmev(f,ev);
    % cancels all monomials in f which are multiples of ev
      dipcancelmev1(f,ev,makedipzero());
 
symbolic procedure dipcancelmev1(f,ev,res);
    if dipzero!? f then res
    else if evmtest!?(dipevlmon f,ev) then
                       dipcancelmev1(dipmred f,ev,res)
     else dipcancelmev1(dipmred f,ev,
       %                 dipAppendMon(res,diplbc f,dipevlmon f));
                         dipnconcmon(res,diplbc f,dipevlmon f));
 
% some prehistoric routines needed in resultant operation
symbolic procedure vevsum0(n,p);
% exponent vector sum version 0. n is the length of vdpvars!*.
% p is a distributive polynomial.
  if vdpzero!? p then vevzero1 n else
  vevsum(vdpevlmon p, vevsum0(n,vdpred p));
 
symbolic procedure vevzero1 n;
% Returns the exponent vector power representation
% of length n for a zero power.
  begin scalar x;
   for i:=1: n do << x := 0 . x >>;
  return x
  end;
 
symbolic procedure vdpresimp u;
   % fi domain changes, the coefficients have to be resimped
   dip2vdp dipresimp vdppoly u;
 
symbolic procedure dipresimp u;
   if null u then nil else
   (for each x in u collect
      <<toggle := not toggle;
      if toggle then simp prepsq x else x>>
      ) where toggle = t;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% printing of polynomials
%
 
symbolic procedure vdpprin2t u; << vdpprint1(u,nil,9999); terpri()>>;

symbolic procedure vdpprin3t u;
      << vdpprint1(u,nil,9999); prin2t ";">>;
 
symbolic procedure vdpprint u; <<vdpprin2 u; terpri()>>;

symbolic procedure vdpprin2 u;
   <<(if x then <<prin2 "P("; prin2 x; 
                  if s then<<prin2 "/",prin2 s>>;
                  prin2 "):  ">>) 
                 where x=vdpgetprop(u,'number),
                       s=vdpgetprop(u,'sugar);
      vdpprint1(u,nil,vdpprintmax)>>;
 
symbolic procedure vdpprint1(u,v,max); vdpprint1x(vdppoly u,v,max);
 
symbolic procedure vdpprint1x(u,v,max);
%   /* Prints a distributive polynomial in infix form.
%     U is a distributive form. V is a flag which is true if a term
%     has preceded current form
%     max limits the number of terms to be printed
   if dipzero!? u then if null v then dipprin2 0 else nil
    else if max = 0 then   % maximum of terms reached
              << terpri();
                 prin2 " ### etc (";
                 prin2 diplength u;
                 prin2 " terms) ###";
                 terpri();>>
    else begin scalar bool,w;
       w := diplbc u;
       if bcminus!? w then <<bool := t; w := bcneg w>>;
       if bool then dipprin2 " - " else if v then dipprin2 " + ";
       (if not bcone!? w or evzero!? x then<<bcprin w; dipevlpri(x,t)>>
         else dipevlpri(x,nil))
           where x = dipevlmon u;
       vdpprint1x(dipmred u,t, max - 1)
     end;
 
symbolic procedure dipprin2 u;
   <<if posn()>69 then terprit 2 ;  prin2 u>>;
    
symbolic procedure vdpsave u; u;
 
%   switching between term order modes
 
symbolic procedure torder2 u; dipsortingmode u;
 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% additional conversion utilities 
 
% conversion dip to standard form / standard quotient

symbolic procedure dip2f u;
      (if denr v neq 1 then
        <<print u;
          rerror(dipoly,9,
                 "Distrib. poly. with rat coeff cannot be converted")>>
       else numr v) where v = dip2sq u;

symbolic procedure dip2sq u;
   % convert a dip into a standard quotient.
     if dipzero!? u then nil ./ 1
     else addsq(diplmon2sq(diplbc u,dipevlmon u),dip2sq dipmred u); 
 
symbolic procedure diplmon2sq(bc,ev);
   %convert a monomial into a standard quotient.
     multsq(bc,dipev2f(ev,dipvars!*) ./ 1);
 
symbolic procedure dipev2f(ev,vars);
     if null ev then 1
     else if car ev = 0 then dipev2f(cdr ev,cdr vars)
     else multf(car vars .** car ev .* 1 .+ nil,
                dipev2f(cdr ev,cdr vars));
     
% evaluate SUBS2 for the coefficients of a dip
 
symbolic procedure dipsubs2 u;
   begin scalar v,secondvalue!*;
      secondvalue!* := 1 ./ 1;
      v := dipsubs21 u;
      return diprectoint(v,secondvalue!*);
   end;
      
symbolic procedure dipsubs21 u;
   begin scalar c;
      if dipzero!? u then return u;
      c := groebsubs2 diplbc u;
      if null numr c then return dipsubs21 dipmred u;
      if not(denr c = 1) then
          secondvalue!* := bclcmd(c,secondvalue!*);
      return dipmoncomp(c,dipevlmon u,dipsubs21 dipmred u);
   end;

% conversion standard form to dip
 
symbolic procedure f2dip u; f2dip1(u,evzero(),bcfd 1);
 
symbolic procedure f2dip1 (u,ev,bc);
  % f to dip conversion: scan the standard form. ev
  % and bc are the exponent and coefficient parts collected
  % so far from higher parts.
   if null u then nil 
   else if domainp u then dipfmon(bcprod(bc,bcfd u),ev)
   else dipsum(f2dip2(mvar u,ldeg u,lc u,ev,bc),
               f2dip1(red u,ev,bc));
 
symbolic procedure f2dip2(var,dg,c,ev,bc);
  % f to dip conversion:
  % multiply leading power either into exponent vector
  % or into the base coefficient.
   <<if ev1 then ev := ev1
     else bc := multsq(bc,var.**dg.*1 .+nil./1);
     f2dip1(c,ev,bc)>>
           where ev1=if memq(var,dipvars!*) then
                evinsert(ev,var,dg,dipvars!*) else nil;
 
symbolic procedure evinsert(ev,v,dg,vars);
   % f to dip conversion:
   % Insert the "dg" into the ev in the place of variable v.
     if null ev or null vars then nil
     else if car vars eq v then dg . cdr ev
     else car ev . evinsert(cdr ev,v,dg,cdr vars);

symbolic procedure vdpcondense f;
   dipcondense car cdddr f;

endmodule;

end;
