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/* ***** This package may be broken. Please use the VECT
package on the SHARE directory. - JPG 6/5/78 ***** */
vector:list$
for f in ["grad","div","curl","laplacian","curlgrad","graddiv",
"divcurl","curlcurl"] do prefix(f,112,expr,expr)$
infix("cross",112,112,expr,expr,expr)$
infix("dotdel",108,108,expr,expr,expr)$
nofix("christoffel",expr)$
dimension():=if dimension=3 then [1,2,3] else [1,2]$
type(arg):=if list= /* check required form of answer */
(if listp(arg) then /* operation performed on a vector */
(for element in arg do /* check each argument */
if listp(element) /* an argument is a list */
then return(list)) /* return a list */
else vector) /* operation performed on a scalar */
then result /* return a list */
else apply('matrix,[result]) /* return a matrix */$
_coordsystem&& coordsystem(sys):=
(if sys=rectangular then
(coodvar:[x,y],
scalefactor:[1,1])
else if sys=polar then
(coordvar:[r,th],
scalefactor:[1,r])
else if sys=cartesian then
(coordvar:[x,y,z],
scalefactor:[1,1,1])
else if sys=cylindrical then
(coordvar:[r,ph,z],
scalefactor:[1,r,1])
else if sys=spherical then
(coordvar:[r,th,ph],
scalefactor:[1,r,r*sin(th)])
else (coordvar:read("coordinate variables"),
scalefactor:read("scale factors")),
dimension:length(coordvar),
coordsystem:sys)$
coordsystem(cartesian)$
_cross&& (a cross b) := if dimension=3 then block([result],
result:[a[2]*b[3]-a[3]*b[2],
a[3]*b[1]-a[1]*b[3],
a[1]*b[2]-a[2]*b[1]],
type([a,b]))
else /* 2 dimensional case */
if nonscalarp(a) then
(if nonscalarp(b) then /* vector x vector */
a[1]*b[2]-a[2]*b[1]
else block([result], /* vector x scalar */
result:[a[2]*b,
-a[1]*b],
type([a])))
else block([result], /* scalar x vector */
result:[-a*b[2],
a*b[1]],
type([b]))$
_grad&& (grad s) := block([result],
result:map(lambda([i],
diff(s,coordvar[i])/scalefactor[i]),
dimension()),
type(vector))$
_div&& (div v) := if dimension=3 then
(diff(scalefactor[2]*scalefactor[3]*v[1],coordvar[1])+
diff(scalefactor[3]*scalefactor[1]*v[2],coordvar[2])+
diff(scalefactor[1]*scalefactor[2]*v[3],coordvar[3]))
/scalefactor[1]/scalefactor[2]/scalefactor[3]
else /* 2 dimensional case */
(diff(scalefactor[2]*v[1],coordvar[1])
+diff(scalefactor[1]*v[2],coordvar[2]))
/scalefactor[1]/scalefactor[2]$
_curl&& (curl a) := if dimension=3 then block([result],
result:[(diff(scalefactor[3]*a[3],coordvar[2])
-diff(scalefactor[2]*a[2],coordvar[3]))
/scalefactor[2]/scalefactor[3],
(diff(scalefactor[1]*a[1],coordvar[3])
-diff(scalefactor[3]*a[3],coordvar[1]))
/scalefactor[3]/scalefactor[1],
(diff(scalefactor[2]*a[2],coordvar[1])
-diff(scalefactor[1]*a[1],coordvar[2]))
/scalefactor[1]/scalefactor[2]],
type([a]))
else /* 2 dimensional case */
if nonscalarp(a) then block([result],
result:(diff(scalefactor[2]*a[2],coordvar[1])
-diff(scalefactor[1]*a[1],coordvar[2]))
/scalefactor[1]/scalefactor[2],
type([a]))
else block([result], /* scalar argument */
result:[diff(a,coordvar[2])/scalefactor[2],
-diff(a,coordvar[1])/scalefactor[1]],
type(vector))$
_laplacian&& (laplacian a) := if nonscalarp(a) then grad div a -curl curl a
else if dimension=3 then
(diff(diff(a,coordvar[1])*scalefactor[2]
*scalefactor[3]/scalefactor[1],coordvar[1])
+diff(diff(a,coordvar[2])*scalefactor[3]
*scalefactor[1]/scalefactor[2],coordvar[2])
+diff(diff(a,coordvar[3])*scalefactor[1]
*scalefactor[2]/scalefactor[3],coordvar[3]))
/scalefactor[1]/scalefactor[2]/scalefactor[3]
else /* 2 dimensional case */
(diff(diff(a,coordvar[1])*scalefactor[2]
/scalefactor[1],coordvar[1])
+diff(diff(a,coordvar[2])*scalefactor[1]
/scalefactor[2],coordvar[2]))/scalefactor[1]/scalefactor[2]$
_dotdel&& (v dotdel b) := if nonscalarp(b) then block([result, b:flatten(args(b)), v:flatten(args(v))],
result:if member('christsym, arrays)
then /* use christoffel symbols */
map(lambda([j],
sum((diff(b[i]*scalefactor[j],
coordvar[i])-sum(b[k]*scalefactor[k]
*christsym[k,j,i],k,1,dimension))
*v[i]/scalefactor[i],i,1,dimension)
/scalefactor[j]),dimension())
else /* vector b, no christoffel symbols */
map(lambda([j],
sum(diff(b[i]*scalefactor[j],coordvar[i])
*v[i]/scalefactor[i],i,1,dimension)
/scalefactor[j]),dimension()),
type([v,b]))
else block([result], /* scalar b case */
result:if member('christsym, arrays)
then /* use christoffel symbols */
sum((diff(b,coordvar[i])-b*christsym[1,1,i])
*v[i]/scalefactor[i],i,1,dimension)
else /* no christoffel symbols */
sum(diff(b,coordvar[i])*v[i]
/scalefactor[i],i,1,dimension),
type([v]))$
_christoffel&& christoffel := (array(christsym,3,3,3),
christsym[i,j,k]:=0,
for i thru 3 do
(christsym[i,i,i]:diff(scalefactor[i],coordvar[i])
/scalefactor[i],
for j thru 3 do if j#i then
(christsym[i,j,i]:christsym[i,i,j]:diff(scalefactor[i],
coordvar[j])/scalefactor[i],
christsym[j,i,i]:-diff(scalefactor[i],
coordvar[j])*scalefactor[i]/scalefactor[j]^2)))$
(curlgrad s) := 0$
(graddiv v) := block([result],
result:div v,
result:map(lambda([i],
diff(result,coordvar[i])/scalefactor[i]),
dimension()),
type(vector))$
(divcurl v) := 0$
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