M + N returns the MultiSet which is the sum of M and N, accounting for multiplicities.  For example, if a has multiplicity 2 in M and 3 in N then it will have multiplicity 5 in M + N.

The M + N + P ... command performs the n-ary sum of the arguments

At least one argument must be a MultiSet for this routine to be invoked.  Any other argument which is expected to be a MultiSet can be a MultiSet, a set or a list; in the latter two cases the argument is converted to a MultiSet before proceeding to evaluate this command.  IsGeneralized(M) must return the same value for all MultiSet arguments M, and all non-MultiSet arguments will be promoted to MultiSets with this same property.

$M≔\mathrm{MultiSet}\left(a=2\,b=5\,c=4\right)$

$M≔\left\{\left[a\,2\right]\,\left[b\,5\right]\,\left[c\,4\right]\right\}$

$N≔\mathrm{MultiSet}\left(a=4\,c=3\,d=7\right)$

$N≔\left\{\left[a\,4\right]\,\left[c\,3\right]\,\left[d\,7\right]\right\}$

$M+N$

$\left\{\left[a\,6\right]\,\left[b\,5\right]\,\left[c\,7\right]\,\left[d\,7\right]\right\}$

$M+N+\left[b\,c\,c\,e\right]$

$\left\{\left[a\,6\right]\,\left[b\,6\right]\,\left[c\,9\right]\,\left[d\,7\right]\,\left[e\,1\right]\right\}$

$M+\mathrm{convert}\left(M\,\mathrm{set}\right)$

$\left\{\left[a\,3\right]\,\left[b\,6\right]\,\left[c\,5\right]\right\}$

The MultiSet/+ operator was introduced in Maple 2016.

For more information on Maple 2016 changes, see Updates in Maple 2016.