Variables

A variable never changes unless you write var mut, and every variable states its type (Values and types).

var needed: Stock = stock_needed(per_pack, packs)var mut total: Stock = neededtotal = Stock(total + holdback)

• var names a value that never changes. var mut names one you can point at a new value of the same type, with name = value.
• Only a var mut local can be assigned. Parameters, fields and declarations can't, because values never change (Values never change).
• A variable is visible from where it is declared to the end of its block.
• A name already in scope, a parameter included, can't be declared again.
• A variable nothing reads is an error.