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grgclass.sl
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%==========================================================================%
% GRGclass.sl Assignment, Macro Functions, Classification %
%==========================================================================%
% GRG 3.2 Standard Lisp Source Code (C) 1988-96 Vadim V. Zhytnikov %
%==========================================================================%
% This file is distributed without any warranty. You may modify it but you %
% are not allowed to remove author's name and/or distribute modified file. %
%==========================================================================%
%------- Assignment Command 09.91,03.94 -------------------------------
%
% Assignment Command in forms
% Tetrad T0=..., ...;
% Tetrad T(j)=..., ...;
% T(j)=..., ...;
% T0=..., ...;
%
(de seti!> (lst)
(prog (w wl wa wr was)
(setq ![newabbr!] nil)
(setq w (seek!> lst '(!=)))
(cond ((or (null w) (null(car w)) (null(cdr w)))
(prog2 (setq ![er!] 2204) (return !!er!!))))
(setq wa (car w))
(setq wl (length wa))
(cond
((or (eqn wl 1) % t0 = ...
(and(eqn wl 2)(pairp(car wa)))) % t(j) = ...
(progn
(setq wa(cond((eqn wl 1) (car wa))
(t (cadr wa))))
(cond((not(idp wa))
(prog2(setq ![er!] 2204)(return !!er!!))))
(setq was wa)
(setq wa (explode2 wa))
(cond((eqn wl 1)(setq wr(selid!> wa nil))))
(setq wa(incomiv!> wa))
(cond((not(flagp wa '!+ivar))
(cond
(wr(progn(doub!> was)(setq ![er!] 8604)(return !!er!!)))
((or(flagp wa '!+grgmac)(gettype!> wa))
(progn(doub!> was)(setq ![er!] 3000)(return !!er!!)))
(t(progn
(cond((flagp was '!+grg)(prog2(doub!> was)(msg!> 8603))))
(setq ![abbr!] (cons wa ![abbr!]))
(setq ![newabbr!] wa)
(global (ncons wa))
(flag (ncons wa) '!+ivar)
(flag (ncons wa) '!+abbr))))))
(return(datr!> lst wa)))) % ---> datr> ...
((atom(car wa))(prog2
(setq w(cons(car wa)(cdr w)))
(setq wa(cdr wa))))
(t (prog2 (setq w(cons(cadr wa)(cons(car wa)(cdr w))))
(setq wa(cddr wa)))))
(setq wa(reverse wa))
(setq was wa)
(setq wa (assocf!> wa ![datl!]))
(cond((or(null wa)(pairp(car wa)))
(progn(setq ![er!] 6030)(doubl!> was)(return !!er!!))))
(setq wa(car wa))
(return(datr!> w wa)))) % ---> datr> ...
% 03.94, 05.96 ... WN - Internal Variable, LST - Text
(de datr!> (lst wn)
(proc (w wl wr ww)
(cond ((null lst) (return nil))
((setq w (constrp!> wn)) % constrained!
(progn (doubo!> wn) (setq ![er!] w) (return !!er!!))))
(setq lst (memlistbr!> '!, lst))
(cond ((eq lst !!er!!) (prog2 (setq ![er!] 2202) (return !!er!!))))
(while!> lst
(setq w (seek1!> (car lst) '!=))
(cond((or (null w) (null(car w)) (null(cdr w)))
(prog2 (setq ![er!] 2204) (return !!er!!))))
(setq wl (reverse (car w)))
(setq wr (cdr w))
(cond((or (not(idp(car wl)))
(and (cdr wl) (not(pairp(cadr wl))))
(greaterp (length wl) 2))
(prog2 (setq ![er!] 2204) (return !!er!!))))
(setq ww
(cond ((cdr wl) (transi!> wn wl wr))
(t (trans!> wn (car wl) wr))))
(cond ((eq ww !!er!!) (cond (![newabbr!] (forget1!> ![newabbr!])))
(return !!er!!)))
(cond
((eq wn '!#!G) (mtype!>))
((eq wn '!#!G!I) (mitype!>))
((eq wn '!#!T) (ftype!>))
((eq wn '!#!D) (fitype!>)))
(setq lst (cdr lst)) )))
% Normal Form ...
% 11.94 ... WN Internal var, WL Left, WR Right
(de trans!> (wn wl wr)
(prog (wi wc)
(cond((and (flagp wn '!+equ) (not(memq '!= wr)))
(prog2 (setq ![er!] 2208) (return !!er!!))))
(setq wi (get wn '!=idxl)) % index types list
(setq wc (transn!> wl wn wi)) % id = ... translation
(cond ((eq wc !!er!!) (return !!er!!)))
(return (trans0!> wn wc wr)) ))
% 11.94 ... WN Internal var, WL indices, WR Right
(de trans0!> (wn wc wr)
(prog (wss wi wt we wnn)
(setq wss (get wn '!=sidxl)) % symmetry list
(setq wi (get wn '!=idxl)) % index types list
(setq wt (gettype!> wn)) % expression type
(cond((null(eval wn)) % prepare space for storing if not exists
(prog2(setq wnn t)(set wn (mkbox!> wn)))))
(cond (wc (setq wc (syaidx!> wc wss))))
(cond((and wi (null wc)) (return nil)))
(setq wr (cschtr!> wr (flagp wn '!+equ)))
(setq ![extvar!] nil)
(cond((flagp wn '!+equ) (setq we (translateeq!> wr))) % expr translation
(t (setq we (translate!> wr))))
(cond ((equal we !!er!!)
(cond (wnn (set wn nil)))
(return !!er!!))
((null we)
(cond ((null wt) (put wn '!=type 0))))
((null wt)
(setq wt (car we))
(put wn '!=type wt))
((not(eqn wt (car we))) % incorrect expression type
(cond(wnn(set wn nil)))
(expects!> wt)
(setq ![er!] 2100) (return !!er!!)))
% storing of the data component
(putel!> (cond(we(cdr we))(t nil)) (eval wn) (cond(wc wc)(t '(0))))
(return t)))
% Perform Sign Changing [CS] and Complex Conjugations [CH] ...
(de cschtr!> (wr we)
(cond((and ![ch!] ![cs!])
(cond (we (progn (setq wr (seek1!> wr '!=))
(list (csch0!>(reverse(car wr))) (csch0!>(cdr wr)))))
(t (csch0!> wr))))
(![cs!]
(cond (we (progn (setq wr (seek1!> wr '!=))
(list (cs0!>(reverse(car wr))) (cs0!>(cdr wr)))))
(t (cs0!> wr))))
(![ch!]
(cond (we (progn (setq wr (seek1!> wr '!=))
(list (ch0!>(reverse(car wr))) (ch0!>(cdr wr)))))
(t (ch0!> wr))))
(t wr)))
% aux functions ...
(de cs0!> (w) (list2 '!- (ncons w)))
(de ch0!> (w) (list2 '!~ (ncons w)))
(de csch0!> (w) (list '!- '!~ (ncons w)))
% Message about wrong type of the expression ...
(de expects!> (wt)
(progn
(cond((eqn wt 0) (prin2 "Algebraic expression"))
((eqn wt -1) (prin2 "Vector"))
(t (prin2 wt) (prin2 "-form")))
(prin2 " is expected.")
(terpri)))
% w - id = ... wn - internal variable wi - index types list
(de transn!> (w wn wi)
(prog(wa wb wc wd wl wf)
(setq wb(explode2 w))
(setq wa(cdr(explode2 wn)))
(setq wf(selid!> wb nil)) % wb - id wf - indices
(cond((not(equal wb wa))
(progn(expid!> wa)(setq ![er!] 2101)(return !!er!!))))
(cond((null wf)(cond((null wi)(return nil)) % scalar data ...
(t(prog2(setq ![er!] 2102)(return !!er!!))))))
(setq wf (mapcar wf 'digorerr!>))
(cond((memq !!er!! wf)
(prog2(setq ![er!] 2102)(return !!er!!))))
(cond ((eq (goodidxl!> wf wi) !!er!!) (return !!er!!)))
(return wf)))
% aux fun ...
(de digorerr!> (w)
(cond((digit w)(compress (ncons w)))
(t !!er!!)))
% w is expected ...
(de expid!> (w)
(progn (mapc w 'prin2)
(prin2 " is expected.")
(terpri)))
% Verifies correct range of indices ...
(de goodidxl!> (wb wi)
(cond ((and (null wb) (null wi)) t)
((null wb) (setq ![er!] 21023) !!er!!)
((null wi) (setq ![er!] 21024) !!er!!)
((lessp (dimid!>(car wi) )(car wb)) (setq ![er!] 21022) !!er!!)
(t (goodidxl!> (cdr wb) (cdr wi)))))
% Verifies correct range the index ...
(de goodid1!> (w wt)
(cond((lessp(dimid!> wt)w) nil)
(t t)))
% Tensorial Form ...
% WN - Internal Variable WL - Left WR - Right
(de transi!> (wn wl wr)
(proc (wt wi w wll wa wii)
(setq wll(cons nil(get wn '!=idxl)))
(setq wt (car wl))
(setq wi (cadr wl))
(setq wt (explode2 wt))
(cond((not(equal wt(cdr(explode2 wn))))
(progn(expid!>(cdr(explode2 wn)))
(setq ![er!] 2101)(return !!er!!))))
(setq wi(memlist!> '!, wi))
(cond((eq wi !!er!!) (prog2(setq ![er!] 2202)(return !!er!!))))
(cond((not(eqn(length wi)(length(get wn '!=idxl))))
(prog2 (cond (![newabbr!] (doubo!> ![newabbr!])
(setq ![er!] 22071))
(t (setq ![er!] 2207)))
(return !!er!!))))
(setq wii nil)
(while!> wi
(setq wii
(cons (prog2 (setq wll(cdr wll)) (sumintr!> (car wi) (car wll)))
wii))
(setq wi (cdr wi)))
(setq wi (reverse wii)) % here now the list of indices in lhs
(cond((memq !!er!! wi)(return !!er!!)))
(setq ![extvar!] (mkextvars!> wi)) % prepare list of ext. vars.
(cond((memq !!er!! ![extvar!]) (return !!er!!))
((null ![extvar!]) % only numerical indices ...
(return (trans0!> wn (mklitind!> wi) wr))))
(cond((flagp wn '!+equ)(setq wr (pretranseq!> wr))) % pre translation
(t (setq wr (pretrans!> wr))))
(cond((eq wr !!er!!)(return !!er!!)))
(setq ![idl!] wi) (setq ![texpr!] wr)
(setq w(cond((null(eval wn))(mkbox!> wn))
(t(eval wn))))
(setq w (errorset!> (list 'allcoll!> (list 'quote w)
(list 'quote wn)
nil
(list 'quote (get wn '!=idxl))
(list 'function 'transel!>)
) ![erst1!] ![erst2!] ))
(remsubindex!> ![idl!])(setq ![texpr!] nil)
(cond((atom w)(prog2(setq ![er!] w)(return !!er!!)))
(t(set wn(car w))))
(return t)))
% Prepare List of Ext. vars ...
(de mkextvars!> (lst)
(cond((null lst) nil)
((atom(car lst))(consmemer!>(car lst)(mkextvars!>(cdr lst))))
(t(appmemer!>(car lst)(mkextvars!>(cdr lst))))))
(de appmemer!> (wa wb)
(prog2 (while!> wa
(setq wb (consmemer!> (car wa)wb))
(setq wa (cdr wa)))
wb))
(de consmemer!> (w lst)
(cond((and(idp w)(memq w lst))
(prog2(setq ![er!] 2205)(cons !!er!! lst)))
((idp w) (cons w lst))
(t lst)))
(de mklitind!> (lst)
(mapcar lst 'mklitind1!>))
(de mklitind1!> (w)
(cond ((numberp w) w)
(t (eval(cons 'plus w)))))
% Translate the element ...
(de transel!> (lst wi wn)
(cond((and (syaidxp!> wi (get wn '!=sidxl))
(coidxp!> wi ![idl!]) )
(progn
(putindex!> wi)
(cond((flagp wn '!+equ)(setq lst(unievaluateeq!> ![texpr!])))
(t (setq lst(unievaluate!> ![texpr!]))))
(remsubindex!> ![idl!])
(cond((null(gettype!> wn))(put wn '!=type (car lst))))
(cond((and lst(not(eqn(car lst)(gettype!> wn))))
(prog2 (expects!>(gettype!> wn))
(err!> 2100))))
(cond(lst(cdr lst))
(t nil))))
(t lst)))
% Summed index treatment if exists ...
(de sumintr!> (w wl)
(cond((atom wl) % tetrad or holonomic index
(cond((or(cdr w)(not(or(idp(car w))(numberp(car w)))))
(prog2(setq ![er!] 2206) !!er!!))
((and(numberp(car w))(not(goodid1!>(car w)wl)))
(prog2(setq ![er!] 21022) !!er!!))
(t(car w))))
((null(cdr w)) % spinor or enumerating index
(cond((not(or(idp(car w))(numberp(car w))))
(prog2(setq ![er!] 2206) !!er!!))
((and(numberp(car w))(not(goodid1!>(car w)wl)))
(prog2(setq ![er!] 21022) !!er!!))
(t(car w))))
(t(prog nil % summed spinor index
(setq w(memlist!> '!+ w))
(cond((or(eq w !!er!!)(not(eqn(length w)(dimid!> wl))))
(prog2(setq ![er!] 2206) (return !!er!!))))
(setq w (mapcar w 'auxfun1!>))
(cond((memq !!er!! w)
(prog2(setq ![er!] 2206)(return !!er!!)))
(t(return w)))))))
(de auxfun1!> (w)
(cond((or (cdr w) (and (not(idp(car w))) (not(numberp(car w)))))
!!er!!)
((and (numberp(car w)) (greaterp(car w)1)) !!er!!)
(t(car w))))
% Compares current list of indices WI with concrete values in WL ...
(de coidxp!> (wi wl)
(cond((and(null wi)(null wl)) t)
(t(and (coidxp1!> (car wi)(car wl))
(coidxp!> (cdr wi)(cdr wl))))))
(de coidxp1!> (wi wl)
(cond((numberp wl)
(cond((eqn wi wl)t)
(t nil)))
((pairp wl)
(prog2 (setq wl (putindex2!> wl))
(cond((or (lessp wi (car wl))
(lessp(length(cdr wl))(difference wi (car wl))))
nil)
(t t))))
(t t)))
% Preparing Ext. vars for translator ...
(de putindex!> (wi)
(proc(w)
(setq w ![idl!])
(while!> wi
(cond((numberp(car w)) nil)
((atom(car w))(put (car w) '!=subind (car wi)))
(t(putindex1!> (car w) (car wi))))
(setq w(cdr w)) (setq wi(cdr wi)))))
(de putindex1!> (wa wb)
(proc nil
(setq wa (putindex2!> wa))
(setq wb (difference wb (car wa)))
(setq wa (cdr wa))
(setq wb (add1 wb))
(while!> wa
(put (car wa) '!=subind
(cond((lessp(length wa)wb) 1)
(t 0)))
(setq wa(cdr wa)))))
(de putindex2!> (w)
(proc (wn wr)
(setq wn 0)
(while!> w
(cond
((numberp(car w)) (setq wn (plus wn (car w))))
(t(setq wr (cons(car w)wr))))
(setq w (cdr w)))
(return(cons wn (reversip wr)))))
% Removing Ext. vars. after translation ...
(de remsubindex!> (w)
(cond((null w) nil)
((pairp(car w))
(prog2 (remsubindex!>(car w)) (remsubindex!>(cdr w))))
((idp(car w))(prog2
(remprop (car w) '!=subind)
(remsubindex!>(cdr w))))
(t(remsubindex!>(cdr w)))))
%----- Macro Functions. 08.01.91, 05.96 -------------------------------
% Solution ...
(de getsoln!> (lst)
(cond((cdr lst) (prog2(doub!> '!S!o!l)(err!> 2105)))
((null(car lst)) (getsoln1!> 0))
((not(zerop(caar lst))) (prog2(doub!> '!S!o!l)(err!> 2023)))
((not(numberp(cdar lst))) (prog2(doub!> '!S!o!l)(err!> 2106)))
(t(getsoln1!> (cdar lst)))))
(de getsoln1!> (wn)
(cond((null ![sol!]) (err!> 2113))
(t(proc (w wnn)
(setq wnn wn)
(setq w ![sol!])
(while!> (and w (not(zerop wn)))
(setq w (cdr w))
(setq wn (sub1 wn)))
(cond((or(null w)(not(zerop wn)))
(prog2 (doub!> wnn) (err!> 2114))))
(return(cona1!> 0 (get1equ!>(car w))))))))
%----- Classify command 06.96 ------------------------------------------
(de classify!> (lst)
(proc (w wc wi)
(cond ((null lst) (return nil)))
(cond ((eq (setq w (dgood!> lst)) !!er!!) (return !!er!!)))
(setq w (altdata!> w))
(while!> w
(setq wc (car w))
(cond
((not(zerop(get wc '!=type)))
(setq ![er!] 9100) (doubo!> wc) (return !!er!!))
((null(eval wc))
(abse!> wc) (go lab)))
(setq wi (get wc '!=idxl))
(cond
((null wi) (cmsg!> wc) (scaltype!> (eval wc)))
((eqn (length wi) 1)
(cond
((eqn (dimid!> (car wi)) 2) (cmsg!> wc) (emtype!> (eval wc)))
((eqn (dimid!> (car wi)) 4) (cmsg!> wc) (petrov!> (eval wc)))
(t (setq ![er!] 9101) (doubo!> wc) (return !!er!!))))
((eqn (length wi) 2)
(cond
((and (eqn (dimid!> (car wi)) 2) (eqn (dimid!> (cadr wi)) 2))
(cmsg!> wc) (riccisclass!> (eval wc)))
((and (eqn (dimid!> (car wi)) 1) (eqn (dimid!> (cadr wi)) 1))
(cmsg!> wc) (vectype!> (eval wc)))
(t (setq ![er!] 9101) (doubo!> wc) (return !!er!!))))
(t (setq ![er!] 9101) (doubo!> wc) (return !!er!!)))
lab
(setq w (cdr w)))))
(de cmsg!> (w)
(progn (gprinreset!>)
(gprils!> '("Classifying"))
(pn0!> w)
(gprils0!> '(":"))
(gterpri!>)))
%----- Petrov classification. 08.01.91, 06.96 --------------------------
(de petrov!> (lst)
(prog (w0 w1 w2 w3 w4 wc wr)
(cond (!*trace
(prin2 "Petrov classification ...") (terpri)
(prin2 " Using algorithm by F.W.Letniowski & R.G.McLenaghan") (terpri)
(prin2 " Gen. Rel. Grav. 20 (1988) 463-483") (terpri)))
(setq w0 (aeval (nz!> (getel1!> lst 0 ))))
(setq w1 (aeval (nz!> (getel1!> lst 1 ))))
(setq w2 (aeval (nz!> (getel1!> lst 2 ))))
(setq w3 (aeval (nz!> (getel1!> lst 3 ))))
(setq w4 (aeval (nz!> (getel1!> lst 4 ))))
(setq wc (plus (times 16 (to1!> w0))
(times 8 (to1!> w1))
(times 4 (to1!> w2))
(times 2 (to1!> w3))
(times 1 (to1!> w4)) ))
(cond (!*trace
(prin2 "Case ") (prin2 wc) (prin2 ": ")
(foreach!> x in (list w0 w1 w2 w3 w4) do (progn
(prin2 " ") (cond ((zerop x) (prin2 0)) (t (prin2 "N")))))
(prin2 " =>")
(terpri) ))
(setq wr
(cond
((eqn wc 0) (finis!> "0" ))
((eqn wc 1) (finis!> "N" ))
((eqn wc 2) (finis!> "III" ))
((eqn wc 3) (finis!> "III" ))
((eqn wc 4) (finis!> "D" ))
((eqn wc 5) (finis!> "II" ))
((eqn wc 6) (finis!> "II" ))
((eqn wc 7) (alter!> (list 'plus (list 'times 2 w3 w3)
(list 'times -3 w2 w4))
"2*W3^2-3*W2*W4" "D" "II"))
((eqn wc 8) (finis!> "III" ))
((eqn wc 9) (finis!> "I" ))
((eqn wc 10) (finis!> "I" ))
((eqn wc 11) (alter!> (list 'plus (list 'times 27 w4 w4 w1)
(list 'times 64 w3 w3 w3))
"27*W4^2*W1+64*W3^3" "II" "I"))
((eqn wc 12) (finis!> "II" ))
((eqn wc 13) (alter!> (list 'plus (list 'times w1 w1 w4)
(list 'times 2 w2 w2 w2))
"W1^2*W4+2*W2^3" "II" "I"))
((eqn wc 14) (alter!> (list 'plus (list 'times 9 w2 w2)
(list 'times -16 w1 w3))
"9*W2^2-16*W1*W3" "II" "I"))
((eqn wc 15) (scase15!> w0 w1 w2 w3 w4))
((eqn wc 16) (finis!> "N" ))
((eqn wc 17) (finis!> "I" ))
((eqn wc 18) (finis!> "I" ))
((eqn wc 19) (alter!> (list 'plus (list 'times w0 w4 w4 w4)
(list 'times -27 w3 w3 w3 w3))
"W0*W4^3-27*W3^4" "II" "I"))
((eqn wc 20) (finis!> "II" ))
((eqn wc 21) (alter!> (list 'plus (list 'times 9 w2 w2)
(list 'times -1 w0 w4))
"9*W2^2-W0*W4" "D" "I"))
((eqn wc 22) (alter!> (list 'plus (list 'times w3 w3 w0)
(list 'times 2 w2 w2 w2))
"W3^2*W0+2*W2^3" "II" "I"))
((eqn wc 23) (scase23!> w0 w1 w2 w3 w4))
((eqn wc 24) (finis!> "III" ))
((eqn wc 25) (alter!> (list 'plus (list 'times w4 w0 w0 w0)
(list 'times -27 w1 w1 w1 w1))
"W4*W0^3-27*W1^4" "II" "I"))
((eqn wc 26) (alter!> (list 'plus (list 'times 27 w0 w0 w3)
(list 'times 64 w1 w1 w1))
"27*W0^2*W3+64*W1^3" "II" "I"))
((eqn wc 27) (scase27!> w0 w1 w2 w3 w4))
((eqn wc 28) (alter!> (list 'plus (list 'times 2 w1 w1)
(list 'times -3 w2 w0))
"2*W1^2-3*W2*W0" "D" "II"))
((eqn wc 29) (scase29!> w0 w1 w2 w3 w4))
((eqn wc 30) (scase30!> w0 w1 w2 w3 w4))
((eqn wc 31) (scase31!> w0 w1 w2 w3 w4))
))
(return wr)))
(de to1!> (w)
(cond ((zerop w) 0)
(t 1)))
(de finis!> (w)
(progn
(prin2 "Petrov type is ")
(prin2 w)
(prin2 ".")
(terpri)
w))
(de alter!> (w wp w0 w1)
(prog2
(setq w (aeval w))
(cond ((zerop w) (iszero!> wp 2) (finis!> w0))
(t (isnonzero!> wp 2 w) (finis!> w1)))))
(de iszero!> (wp wl)
(cond (!*trace
(spaces wl)
(prin2 wp)
(prin2 " = 0 =>")
(terpri))))
(de isnonzero!> (wp wl w)
(cond (!*trace
(spaces wl)
(prin2 wp)
(cond (!*showexpr
(prin2 " = ") (terpri)
(algpri!> " ") (algpri!> w) (algterpri!>)
(spaces (sub1 wl))))
(prin2 " is nonzero =>")
(terpri))))
(de zt!> (we wp wl)
(cond ((zerop we) (prog2 (iszero!> wp wl) t))
(t (prog2 (isnonzero!> wp wl we) nil))))
(de scase15!> (w0 w1 w2 w3 w4)
(prog (wi wf1 wf2 wdh)
(setq wi (aeval (list 'plus (list 'times 3 w2 w2)
(list 'times -4 w1 w3))))
(setq wf1 (aeval (list 'plus (list 'times 2 w2 w3)
(list 'times -3 w1 w4))))
(cond
((zt!> wi "I=3*W2^2-4*W1*W3" 2)
(cond
((zt!> wf1 "F1=2*W2*W3-3*W1*W4" 4) (return(finis!> "III")))
(t (return(finis!> "I")))))
(t (cond
((zt!> wf1 "F1=2*W2*W3-3*W1*W4" 4) (return(finis!> "I")))
(t (setq wf2 (aeval (list 'plus (list 'times 9 w2 w4)
(list 'times -8 w3 w3))))
(cond
((zt!> wf2 "F2=9*W2*W4-8*W3^2" 6) (return(finis!> "I")))
(t (setq wdh (aeval (list 'plus (list 'times 3 wf1 wf1)
(list 'times 2 wi wf2))))
(cond
((zt!> wdh "D^=3*F1^2+2*I*F2" 8)
(return(finis!> "II")))
(t (return(finis!> "I"))))))))))))
(de scase30!> (w0 w1 w2 w3 w4)
(prog (wi wf1 wf2 wdh)
(setq wi (aeval (list 'plus (list 'times 3 w2 w2)
(list 'times -4 w1 w3))))
(setq wf1 (aeval (list 'plus (list 'times 2 w2 w1)
(list 'times -3 w3 w0))))
(cond
((zt!> wi "I=3*W2^2-4*W1*W3" 2)
(cond
((zt!> wf1 "F1=2*W2*W1-3*W3*W0" 4) (return(finis!> "III")))
(t (return(finis!> "I")))))
(t (cond
((zt!> wf1 "F1=2*W2*W1-3*W3*W0" 4) (return(finis!> "I")))
(t (setq wf2 (aeval (list 'plus (list 'times 9 w2 w0)
(list 'times -8 w1 w1))))
(cond
((zt!> wf2 "F2=9*W2*W0-8*W1^2" 6) (return(finis!> "I")))
(t (setq wdh (aeval (list 'plus (list 'times 3 wf1 wf1)
(list 'times 2 wi wf2))))
(cond
((zt!> wdh "D^=3*F1^2+2*I*F2" 8)
(return(finis!> "II")))
(t (return(finis!> "I"))))))))))))
(de scase23!> (w0 w1 w2 w3 w4)
(prog (wi wjh wf3 wdt)
(setq wi (aeval (list 'plus (list 'times w0 w4)
(list 'times 3 w2 w2))))
(setq wjh (aeval (list 'plus (list 'times 4 w2 w4)
(list 'times -3 w3 w3))))
(cond
((zt!> wi "I=W0*W4+3*W2^2" 2)
(cond
((zt!> wjh "J^=4*W2*W4-3*W3^2" 4) (return(finis!> "III")))
(t (return(finis!> "I")))))
(t (cond
((zt!> wjh "J^=4*W2*W4-3*W3^2" 4) (return(finis!> "I")))
(t (setq wf3 (aeval (list 'plus (list 'times w0 wjh)
(list 'times -2 w2 wi ))))
(cond
((zt!> wf3 "F3=W0*J^-2*W2*I" 6) (return(finis!> "I")))
(t (setq wdt (aeval (list 'plus (list 'times w4 wi wi)
(list 'times -3 wjh wf3))))
(cond
((zt!> wdt "D~=W4*I^2-3*J^*F3" 8)
(return(finis!> "II")))
(t (return(finis!> "I"))))))))))))
(de scase29!> (w0 w1 w2 w3 w4)
(prog (wi wjh wf3 wdt)
(setq wi (aeval (list 'plus (list 'times w0 w4)
(list 'times 3 w2 w2))))
(setq wjh (aeval (list 'plus (list 'times 4 w2 w0)
(list 'times -3 w1 w1))))
(cond
((zt!> wi "I=W0*W4+3*W2^2" 2)
(cond
((zt!> wjh "J^=4*W2*W0-3*W1^2" 4) (return(finis!> "III")))
(t (return(finis!> "I")))))
(t (cond
((zt!> wjh "J^=4*W2*W0-3*W1^2" 4) (return(finis!> "I")))
(t (setq wf3 (aeval (list 'plus (list 'times w4 wjh)
(list 'times -2 w2 wi ))))
(cond
((zt!> wf3 "F3=W4*J^-2*W2*I" 6) (return(finis!> "I")))
(t (setq wdt (aeval (list 'plus (list 'times w0 wi wi)
(list 'times -3 wjh wf3))))
(cond
((zt!> wdt "D~=W0*I^2-3*J^*F3" 8)
(return(finis!> "II")))
(t (return(finis!> "I"))))))))))))
(de scase27!> (w0 w1 w2 w3 w4)
(prog (wv wu ww wi wj wd)
(setq wv (aeval (list 'plus (list 'times w0 w3 w3)
(list 'times -1 w1 w1 w4))))
(cond
((zt!> wv "V=W0*W3^3-W1^2*W4" 2)
(setq wu (aeval (list 'plus (list 'times w0 w4)
(list 'times 2 w1 w3))))
(cond
((zt!> wu "U=W0*W4+2*W1*W3" 4) (return(finis!> "D")))
(t
(setq ww (aeval (list 'plus (list 'times w0 w4)
(list 'times -16 w1 w3))))
(cond
((zt!> ww "W=W0*W4-16*W1*W3" 6) (return(finis!> "II")))
(t (return(finis!> "I")))))))
(t
(setq wi (aeval (list 'plus (list 'times w0 w4)
(list 'times -4 w1 w3))))
(setq wj (aeval (list 'plus (list 'times -1 w0 w3 w3)
(list 'times -1 w1 w1 w4))))
(cond
((ZT!> WI "I=W0*W4-4*W1*W3" 4)
(cond
((zt!> wj "J=-W0*W3^2-W1^2*W4" 6) (return(finis!> "III")))
(t (return(finis!> "I")))))
((zt!> wj "J=-W0*W3^2-W1^2*W4" 6) (return(finis!> "I")))
(t
(setq wd (aeval (list 'plus (list 'times wi wi wi)
(list 'times -27 wj wj ))))
(cond
((zt!> wd "D=I^3-27*J^2" 8) (return(finis!> "II")))
(t (return(finis!> "I"))))))))))
(de scase31!> (w0 w1 w2 w3 w4)
(prog (wh wf we wa wi wq wj wg wz wss wd)
(setq wh (aeval (list 'plus (list 'times w0 w2 )
(list 'times -1 w1 w1 ))))
(cond
((zt!> wh "H=W0*W2-W1^2" 2)
(setq wf (aeval (list 'plus (list 'times w0 w3 )
(list 'times -1 w1 w2 ))))
(setq we (aeval (list 'plus (list 'times w0 w4 )
(list 'times -1 w2 w2 ))))
(cond
((zt!> wf "F=W0*W3-W1*W2" 4)
(cond
((zt!> we "E=W0*W4-W2^2" 6) (return(finis!> "N")))
(t (return(finis!> "I")))))
((zt!> we "E=W0*W4-W2^2" 6)
(setq wq (aeval (list 'plus (list 'times 37 w2 w2 )
(list 'times 27 w1 w3 ))))
(cond
((zt!> wq "Q=37*W2^2+27*W1*W3" 8) (return(finis!> "II")))
(t (return(finis!> "I")))))
(t
(setq wa (aeval (list 'plus (list 'times w1 w3 )
(list 'times -1 w2 w2 ))))
(setq wi (aeval (list 'plus we (list 'times -4 wa ))))
(cond
((zt!> wi "A=W1*W3-W2^2; I=E-4*A" 8) (return(finis!> "I")))
(t
(setq wj (aeval (list 'plus (list 'times w4 wh )
(list 'times -1 w3 wf )
(list 'times w2 wa ))))
(setq wd (aeval (list 'plus (list 'times wi wi wi )
(list 'times -27 wj wj ))))
(cond
((zt!> wd "J=W4*H-W3*F+W2*A; D=I^3-27*J^2" 10)
(return(finis!> "II")))
(t (return(finis!> "I")))))))))
(t
(setq wf (aeval (list 'plus (list 'times w0 w3 )
(list 'times -1 w1 w2 ))))
(setq we (aeval (list 'plus (list 'times w0 w4 )
(list 'times -1 w2 w2 ))))
(setq wa (aeval (list 'plus (list 'times w1 w3 )
(list 'times -1 w2 w2 ))))
(setq wi (aeval (list 'plus we (list 'times -4 wa ))))
(cond
((zt!> wi "E=W0*W4-W2^2; A=W1*W3-W2^2; I=E-4*A" 4)
(setq wf (aeval (list 'plus (list 'times w0 w3 )
(list 'times -1 w1 w2 ))))
(setq wj (aeval (list 'plus (list 'times w4 wh )
(list 'times -1 w3 wf )
(list 'times w2 wa ))))
(cond
((zt!> wj "F=W0*W3-W1*W2; J=W4*H-W3*F+W2*A" 6)
(return(finis!> "III")))
(t (return(finis!> "I")))))
(t
(setq wf (aeval (list 'plus (list 'times w0 w3 )
(list 'times -1 w1 w2 ))))
(setq wg (aeval (list 'plus (list 'times w0 wf )
(list 'times -2 w1 wh ))))
(cond
((zt!> wg "G=W0*F-2*W1*H" 6)
(setq wz (aeval (list 'plus (list 'times w0 w0 wi )
(list 'times -12 wh wh ))))
(cond
((zt!> WZ "Z=W0^2*I-12*H^2" 8) (return(finis!> "D")))
(t
(setq wss (aeval (list 'plus (list 'times w0 w0 wi )
(list 'times -3 wh wh ))))
(cond
((zt!> wss "S=W0^2*I-3*H^2" 10)
(return(finis!> "II")))
(t (return(finis!> "I")))))))
(t
(setq wj (aeval (list 'plus (list 'times w4 wh )
(list 'times -1 w3 wf )
(list 'times w2 wa ))))
(cond
((zt!> wj "J=W4*H-W3*F+W2*A" 8) (return(finis!> "I")))
(t
(setq wd (aeval (list 'plus (list 'times wi wi wi )
(list 'times -27 wj wj ))))
(cond
((zt!> wd "D=I^3-27*J^3" 10)
(return(finis!> "II")))
(t (return(finis!> "I"))))))))))))))
%------- EM Type 06.96 ----------------------------------------------------
(de emtype!> (lst)
(prog (w0 w1 w2 wc wr wd)
(cond (!*trace
(prin2 "EM strength classification ...") (terpri)))
(setq w0 (aeval (nz!> (getel1!> lst 0 ))))
(setq w1 (aeval (nz!> (getel1!> lst 1 ))))
(setq w2 (aeval (nz!> (getel1!> lst 2 ))))
(setq wc (plus (times 4 (to1!> w0))
(times 2 (to1!> w1))
(times 1 (to1!> w2)) ))
(cond (!*trace
(prin2 "Case ") (prin2 wc) (prin2 ": ")
(foreach!> x in (list w0 w1 w2) do (progn
(prin2 " ") (cond ((zerop x) (prin2 0)) (t (prin2 "N")))))
(prin2 " =>")
(terpri) ))
(setq wr
(cond
((eqn wc 0) (emfinis!> "0"))
((eqn wc 1) (emfinis!> "N"))
((eqn wc 2) (emfinis!> "I"))
((eqn wc 3) (emfinis!> "I"))
((eqn wc 4) (emfinis!> "N"))
((eqn wc 5) (emfinis!> "I"))
((eqn wc 6) (emfinis!> "I"))
((eqn wc 7)
(setq wd (aeval (list 'plus (list 'times w0 w2)
(list 'times -1 w1 w1))))
(cond
((zt!> wd "D=F0*F2-F1^2" 2) (emfinis!> "N"))
(t (emfinis!> "I"))))))
(return wr)))
(de emfinis!> (w)
(progn
(prin2 "EM type is ")
(prin2 w)
(prin2 ".")
(terpri)
w))
%------- Ricci spinor classification 06.96 --------------------------------
(de riccisclass!> (lst)
(prog (f00 f01 f02 f11 f12 f22 w0 w1 w2 w3 w4 wc wr wpp wi6 ww
wq ws1 ws2 ws3 ws4 ws5 ws6 ws7 wip wi7)
(cond (!*trace
(prin2 "Ricci Spinor classification ...") (terpri)
(prin2 " Using algorithm by G.C.Joly, M.A.H.McCallum & W.Seixas") (terpri)
(prin2 " Class. Quantum Grav. 7 (1990) 541-556") (terpri)
(prin2 " Class. Quantum Grav. 8 (1991) 1577-1585") (terpri)))
(setq f00 (aeval (nz!> (getel2!> lst 0 0))))
(setq f01 (aeval (nz!> (getel2!> lst 0 1))))
(setq f02 (aeval (nz!> (getel2!> lst 0 2))))
(setq f11 (aeval (nz!> (getel2!> lst 1 1))))
(setq f12 (aeval (nz!> (getel2!> lst 1 2))))
(setq f22 (aeval (nz!> (getel2!> lst 2 2))))
(setq wc (mapcar (list f00 f01 f02 f11 f12 f22) 'to1!>))
(cond (!*trace
(prin2 "Case ")
(foreach!> x in wc do (prin2 x))
(prin2 " =>")
(terpri) ))
% Special cases ...
(setq wr
(cond
((equal wc '(0 0 0 0 0 0)) (rfin!> "0" "[(1111)]"))
((equal wc '(0 0 0 1 0 0)) (rfin!> "D" "[(11)(1,1)]"))
((equal wc '(0 0 1 0 0 0)) (rfin!> "D" "[11(1,1)]"))
((equal wc '(0 0 0 0 0 1)) (rfin!> "0" "[(112)]"))
((equal wc '(1 0 0 0 0 0)) (rfin!> "0" "[(112)]"))
((equal wc '(0 0 0 1 0 1)) (rfin!> "D" "[(11)2]"))
((equal wc '(1 0 0 1 0 0)) (rfin!> "D" "[(11)2]"))
((equal wc '(0 0 1 0 0 1)) (rfin!> "II" "[112]"))
((equal wc '(1 0 1 0 0 0)) (rfin!> "II" "[112]"))
((equal wc '(0 0 0 0 1 0)) (rfin!> "N" "[(13)]"))
((equal wc '(0 1 0 0 0 0)) (rfin!> "N" "[(13)]"))
((equal wc '(0 0 0 1 1 0)) (rfin!> "D" "[(11)2]"))
((equal wc '(0 1 0 1 0 0)) (rfin!> "D" "[(11)2]"))
((equal wc '(0 0 0 0 1 1)) (rfin!> "N" "[(13)]"))
((equal wc '(1 1 0 0 0 0)) (rfin!> "N" "[(13)]"))
((equal wc '(0 1 0 0 0 1)) (rfin!> "I" "[11ZZ~]"))
((equal wc '(1 0 0 0 1 0)) (rfin!> "I" "[11ZZ~]"))
))
(cond (wr (return wr)))
% General case ...
% PP type first ...
(setq w0 (aeval(wff!> 0 lst)))
(setq w1 (aeval(wff!> 1 lst)))
(setq w2 (aeval(wff!> 2 lst)))
(setq w3 (aeval(wff!> 3 lst)))
(setq w4 (aeval(wff!> 4 lst)))
(cond (!*trace
(prin2 "Making Petrov-Plebanski (PP) classification ...")
(terpri)))
(setq wpp (petrov!> (list w0 w1 w2 w3 w4)))
% Segre type ...
(setq wr
(cond
((equal wpp "0" )
(setq ww (aeval (list 'plus
(list 'times f11 f11)
(list 'times -1 f12 (gfab!> 1 0 lst)))))
(cond
((zt!> ww "W=F11'^2-F10'*F12'" 2) (rfin!> wpp "[(112)]"))
((zt!> f00 "F00" 4) (rfin!> wpp "[1(11,1)]"))
((zt!> f22 "F22" 4) (rfin!> wpp "[1(11,1)]"))
(t (rfincond!> wpp "[(111),1]"
" if W>0 and "
"[1(11,1)]"
" if W<0"))))
((equal wpp "I" ) (rfincond!> wpp "[111,1]"
" if D>0 and "
"[11ZZ~]"
" if D<0"))
((equal wpp "II" ) (rfin!> wpp "[112]"))
((equal wpp "III") (rfin!> wpp "[13]"))
((equal wpp "N" )
(setq wi6 (aeval (list 'plus
(list 'times (gfab!> 0 0 lst) (gfab!> 2 2 lst))
(list 'times 2 (gfab!> 1 1 lst) (gfab!> 1 1 lst))
(list 'times -2 (gfab!> 0 1 lst) (gfab!> 2 1 lst))
(list 'times -2 (gfab!> 1 0 lst) (gfab!> 1 2 lst))
(list 'times (gfab!> 0 2 lst) (gfab!> 2 0 lst)))))
(cond
((zt!> wi6 "I6" 2) (rfin!> wpp "[(13)]"))
(t (rfin!> wpp "[1(12)]"))))
((equal wpp "D" )
(setq wi6 (aeval (list 'plus
(list 'times (gfab!> 0 0 lst) (gfab!> 2 2 lst))
(list 'times 2 (gfab!> 1 1 lst) (gfab!> 1 1 lst))
(list 'times -2 (gfab!> 0 1 lst) (gfab!> 2 1 lst))
(list 'times -2 (gfab!> 1 0 lst) (gfab!> 1 2 lst))
(list 'times (gfab!> 0 2 lst) (gfab!> 2 0 lst)))))
(cond
((zt!> wi6 "I6" 2) (rfin!> wpp "[(11)ZZ~]"))
(t
(setq wip (aeval (list 'plus
(list 'times w0 w4)
(list 'times -4 w1 w3)
(list 'times 3 w2 w2))))
(setq ww (aeval (list 'plus
(list 'times f11 f11)
(list 'times -1 f12 (gfab!> 1 0 lst)))))
(setq wq (aeval
(list 'plus wip
(list 'times -3 (list 'expt (list 'plus w2 ww) 2)))))
(cond
((zt!> wq "Q" 4)
(setq ws1 (aeval (list 'plus
(list 'times (gfab!> 2 0 lst) (gfab!> 1 2 lst))
(list 'times -1 (gfab!> 1 0 lst) (gfab!> 2 2 lst)))))
(setq ws2 (aeval (list 'plus
(list 'times (gfab!> 0 0 lst) (gfab!> 2 2 lst))
(list 'times -1 (gfab!> 2 0 lst) (gfab!> 0 2 lst)))))
(setq ws3 (aeval (list 'plus
(list 'times (gfab!> 1 0 lst) (gfab!> 0 2 lst))
(list 'times -1 (gfab!> 0 0 lst) (gfab!> 1 2 lst)))))
(setq ws4 (aeval (list 'plus
(list 'times (gfab!> 0 0 lst) (gfab!> 1 1 lst))
(list 'times -1 (gfab!> 1 0 lst) (gfab!> 0 1 lst)))))
(setq ws5 (aeval (list 'plus
(list 'times (gfab!> 0 1 lst) (gfab!> 1 2 lst))
(list 'times -1 (gfab!> 0 2 lst) (gfab!> 1 1 lst)))))
(setq ws6 (aeval (list 'plus
(list 'times (gfab!> 1 1 lst) (gfab!> 2 2 lst))
(list 'times -1 (gfab!> 1 2 lst) (gfab!> 2 1 lst)))))
(setq wi7 (aeval (list 'plus
(list 'times f01 ws1)
(list 'times f11 ws2)
(list 'times (gfab!> 2 1 lst) ws3))))
(cond
((and (zt!> ws1 "S1" 6)
(zt!> ws2 "S2" 6)
(zt!> ws3 "S3" 6))
(cond
((and (zt!> ws4 "S4" 6)
(zt!> ws5 "S5" 6)
(zt!> ws6 "S6" 6))
(rfin!> wpp "[(11)(1,1)]"))
(t (rfin!> wpp "[(11)2]"))))
((zt!> wi7 "I7" 6) (rfin!> wpp "[(11)2]"))
(t (rfin!> wpp "[11ZZ~]"))))
(t (rfincond!> wpp "[(11)ZZ~]"
" if S7<0 and "
"[(11)1,1] or [11(1,1)]"
" if S7>0"))))
))))
(return wr)))