% Problem parameters
enum TOYS;@\Vlabel{line:back-knap-toys}@
array[TOYS] of int: toy_joy;@\Vlabel{line:back-knap-joy}@
array[TOYS] of int: toy_space;@\Vlabel{line:back-knap-space}@
int: space_left;@\Vlabel{line:back-knap-left}@

% Decision variables
var set of TOYS: selection;@\Vlabel{line:back-knap-sel}@
var int: total_joy = sum(toy in selection)(toy_joy[toy]);@\Vlabel{line:back-knap-tj}@

% Constraints
constraint sum(toy in selection)(toy_space[toy]) < space_left;@\Vlabel{line:back-knap-con}@

% Goal
solve maximize total_joy;@\Vlabel{line:back-knap-obj}@