Singular Manual: prune_map

  | ### 5.1.123 prune_map `Syntax:` `prune_map(` module_expression `,` smatrix_name `)` `Type:` module `Purpose:` returns the module minimally embedded in a free module such that the corresponding factor modules are isomorphic together with the map (as matrix) `Note:` If for the input module the attribute `"isHomog"` is set, `prune` also sets the attribute `"isHomog"`. For non-global orderings, only reduction steps with constant units are performed. Hence, the returned module does not need to be minimal. `Example:`
        ring r=0,(x,y,z),dp;
        module m=gen(1),gen(3),[x,y,0,z],[x+y,0,0,0,1];
        smatrix M;
        print(m);
      ==> 1,0,x,x+y,
      ==> 0,0,y,0,
      ==> 0,1,0,0,
      ==> 0,0,z,0,
      ==> 0,0,0,1
        print(prune_map(m,M)); // pruned module
      ==> v[1]:1 v[2]:1 v[3]:2 v[4]:2 v[5]:3
      ==> y,
      ==> z
        print(m*M); // apply map
      ==> 0,
      ==> y,
      ==> 0,
      ==> z,
      ==> 0
        print(M); // map
      ==> -x,
      ==> 0,
      ==> 1,
      ==> 0
See module.

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