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2.2.3 map operations
( )
- composition of maps. If, for example,
f and g are maps,
then f(g) is a map expression giving the composition of f
and g .
- map_expression
[ int_expressions ]
- is a map entry (the image of the corresponding variable)
Example:
| LIB "ncalg.lib";
def Usl2 = sl2();
setring Usl2;
map F=Usl2,f,e,-h; // check the automorphism of U(sl_2)
map G=F(F);
poly p = (f+e*h)^2 + 3*h-e;
p;
==> e2h2+2e2h+2efh-2ef+f2-h2-e+3h
F(p);
==> f2h2-2efh-2f2h+e2-2ef+h2-f-h
G(p);
==> e2h2+2e2h+2efh-2ef+f2-h2-e+3h
(G(p) == p); // G is the identity
==> 1
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