The command Symbols(vc) returns as a list the variables occurring in the constraints of a value-under-constraints object.

$\mathrm{with}\left(\mathrm{ValuesUnderConstraints}\right)\:$

$\mathrm{vc1}≔\mathrm{ValueUnderConstraints}\left(\left[1\right]\,\left[a\,b\,c\,d\right]\,\left[a\right]\,\left[b\right]\,\left[c\right]\,\left[d\right]\,\varnothing \right)$

$\mathrm{vc1}≔⟨\text{value}\left\{1\right\}\text{when}\left[a=0\&comma;d\ne 0\&comma;0<c\&comma;0\le b\right]⟩$

$\mathrm{Value}\left(\mathrm{vc1}\right)\&semi;$$\mathrm{Constraints}\left(\mathrm{vc1}\right)\&semi;$$\mathrm{Symbols}\left(\mathrm{vc1}\right)\&semi;$$\mathrm{IntegerSymbols}\left(\mathrm{vc1}\right)$

$\left\{1\right\}$

$\left[a=0\&comma;d\ne 0\&comma;0<c\&comma;0\le b\right]$

$\left[a\&comma;b\&comma;c\&comma;d\right]$

$\varnothing$

$\mathrm{vc2}≔\mathrm{ValueUnderConstraints}\left(\left[2\right]\&comma;\left[a\&comma;b\&comma;c\&comma;d\right]\&comma;\left[a\right]\&comma;\left[b\right]\&comma;\left[c\right]\&comma;\left[d\right]\&comma;\left\{a\&comma;b\&comma;c\&comma;d\right\}\right)$

$\mathrm{vc2}≔⟨\text{value}\left\{2\right\}\text{when}\left[a=0\&comma;d\ne 0\&comma;0\le b\&comma;0\le c-1\right]⟩$

$\mathrm{Value}\left(\mathrm{vc2}\right)\&semi;$$\mathrm{Constraints}\left(\mathrm{vc2}\right)\&semi;$$\mathrm{Symbols}\left(\mathrm{vc2}\right)\&semi;$$\mathrm{IntegerSymbols}\left(\mathrm{vc2}\right)$

$\left\{2\right\}$

$\left[a=0\&comma;d\ne 0\&comma;0\le b\&comma;0\le c-1\right]$

$\left[a\&comma;b\&comma;c\&comma;d\right]$

$\left\{a\&comma;b\&comma;c\&comma;d\right\}$

Rui-Juan Jing, Yuzhuo Lei, Christopher F. S. Maligec, Marc Moreno Maza: "Counting the Integer Points of Parametric Polytopes: A Maple Implementation." Proceedings of Computer Algebra in Scientific Computing - 26th International Workshop (CASC) 2024: 140-160, Lecture Notes in Computer Science, vol. 14938, Springer.

The ValuesUnderConstraints[Symbols] command was introduced in Maple 2025.

For more information on Maple 2025 changes, see Updates in Maple 2025.