up previous next
image [OBSOLESCENT]

[OBSOLESCENT] apply ring homomorphism

Syntax 
Image(V: OBJECT, F:TAGGED("RMap")): OBJECT

Description
In CoCoA-5 homomorphisms are properly implemented as RINGHOM . Image was the CoCoA-4 function mimicking homomorphisms, in particular PolyAlgebraHom .

Example 
/**/  Use D ::= QQ[x,y];   -- domain
/**/  f := x-y;   -- a RINGELEM in D

/**/  Use C ::= QQ[a,b,c]; -- codomain

/**/  -- the old trick
/**/  Phi := RMap(a, c^2-a*b);  -- OBSOLESCENT
/**/  Image(f, Phi);            -- OBSOLESCENT
a*b -c^2 +a

/**/  -- the proper call
/**/  phi := PolyAlgebraHom(D, C, [a, c^2-a*b]);  -- a RINGHOM
/**/  phi(f);
a*b -c^2 +a

See Also