4.12.3 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,
provided the target ring of g is the basering of f.

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