For a permutation P from perm_var(), item_at(slot, P) is the item in
a slot, and slot_of(item, P) is the slot that an item is in. For a route
whose items are stops and whose slots are the visits, item_at(1, route)
is the first stop visited, and slot_of(3, route) is when stop 3 is
visited.
Arguments
- slot, item
Whole numbers from 1 to the size of the permutation.
- P
A permutation from
perm_var().
Value
An expression with one element per element of the first argument, each a whole number from 1 to the size of the permutation.
Details
The result is an expression whose value the service chooses, like the
value of a decision variable. To use it to read data, such as the distance
between two stops, index a lookup_table() with it.
The first argument is a plain number, or a vector of numbers, and both
functions return one element per number: item_at(1:4, P) is the items in
the first four slots, an expression of length 4.
Examples
m <- model()
route <- perm_var(m, "route", 5)
item_at(1, route) # the first stop visited
#> item_at(1, route)
slot_of(3, route) # when stop 3 is visited
#> slot_of(3, route)
item_at(1:4, route) # the first four stops visited
#> [1] item_at(1, route)
#> [2] item_at(2, route)
#> [3] item_at(3, route)
#> [4] item_at(4, route)