[lectures] Update generics slides.
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@ -3,13 +3,13 @@ generics
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Арсений Балобанов
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* Generics (draft)
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* Generics
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* New language features
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- Mechanism to parameterize a type or function by types.
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- Constraints mechanism to express requirements on type parameters.
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- Type inference (optional)
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- Type parameters for functions and types
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- Type sets
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- Type inference
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* Parameter lists
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@ -23,6 +23,108 @@ A type parameter list
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- Convention: Type parameter names are capitalized
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* min
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.play -edit min/basic/min.go /^func min/,/^}/
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* Generic min
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.play -edit min/basic/min.go /^func min/,/^}/
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.play -edit min/generic/min.go /^func min/,/^}/
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* Calling generic min
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m := min[int](1, 2)
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* Instantiation
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fmin := min[float64] // non generic
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m := fmin(2.71, 3.14)
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* Generic type
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type Tree[T interface{}] struct {
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left, right *Tree[T]
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data T
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}
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func (t *Tree[T]) Lookup(x T) *Tree[T]
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var stringTree Tree[string]
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- Methods cannot have it's own type parameters
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* Type sets
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func min(x, y float64) float64
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- float64 defines a set of values x and y can have
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func min[T constraints.Ordered](x, y T) T {
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- constraints.Ordered defines a set of values T can have
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* constaints.Ordered
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// Ordered is a constraint that permits any ordered type: any type
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// that supports the operators < <= >= >.
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// If future releases of Go add new ordered types,
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// this constraint will be modified to include them.
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type Ordered interface {
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Integer | Float | ~string
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}
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- The < operator is supported by every type in this subset
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- ~T means with underlying type T
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* constaints
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type Signed interface {
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~int | ~int8 | ~int16 | ~int32 | ~int64
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}
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type Unsigned interface {
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~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr
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}
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type Integer interface {
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Signed | Unsigned
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}
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type Float interface {
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~float32 | ~float64
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}
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type Complex interface {
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~complex64 | ~complex128
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}
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* Constaints & type sets
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[T aConstraint]
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- aConstraint is an interface
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- interface has a type set
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- type set defines the types that are permissible
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* Constaint literals
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[S interface{~[]E}, E interface{}]
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- interface{E} could be rewritten as E in a constraint
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[S ~[]E, E interface{}]
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- any is a new predeclared identifier — an alias for interface{} in a constraint
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[S ~[]E, E any]
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* Type inference
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- Type intefence is complicated but usage is simple
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- Programms that don't need type arguments today won't need them tomorrow
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* Sorting in Go
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what we have
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@ -108,10 +210,10 @@ Invocation (as usual)
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* Types can be generic, too
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type Lesser[T any] interface{
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Less(y T) bool}
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Less(y T) bool
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}
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any stands for "no constraint"(same as "interface{}")
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any stands for "no constraint" (same as "interface{}")
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* Sort, decomposed
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@ -133,7 +235,7 @@ any stands for "no constraint"(same as "interface{}")
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- type of list[i], list[j] is Elem
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- Elem is NOT an interface type!
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- A type parameter is a real type.It is not an interface type.
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- A type parameter is a real type. It is not an interface type.
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* Argument type inference
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@ -247,11 +349,6 @@ Use
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- Type inference (if applicable) makes function instantiation implicit.
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- Instantiation is valid if the type arguments satisfy their constraints.
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* How to try?
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.link https://go2goplay.golang.org/ - playground
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.link https://go.googlesource.com/go/+/refs/heads/dev.go2go/README.go2go.md - dev branch
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* Ссылки
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.link https://go.googlesource.com/proposal/+/refs/heads/master/design/go2draft-contracts.md - generics design draft
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