|  |  4.11.3 map operations 
 
 
( )composition of maps. If, for example, fandgare maps,
thenf(g)is a map expression giving the composition of fandg,provided the target ring of
 gis the basering off.
map_expression [int_expressions]is a map entry (the image of the corresponding variable)
 
Example:
 |  |   ring r=0,(x,y),dp;
  map f=r,y,x;    // the map f permutes the variables
  f;
==> f[1]=y
==> f[2]=x
  poly p=x+2y3;
  f(p);
==> 2x3+y
  map g=f(f);    // the map g defined as  f^2 is the identity
  g;
==> g[1]=x
==> g[2]=y
  g(p) == p;
==> 1
 | 
 
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