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Go 2 generic syntax readability: replace () with [] #39684

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kokizzu opened this issue Jun 18, 2020 · 3 comments
Closed

Go 2 generic syntax readability: replace () with [] #39684

kokizzu opened this issue Jun 18, 2020 · 3 comments

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@kokizzu
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@kokizzu kokizzu commented Jun 18, 2020

Personally () parentheses seems like to be harder to read, too similar with function calls.

It would be nicer if we use brackets instead [] like in Nim, since [] only used in array/slice/indexing (index key or empty), which is more readable than () that used in many ways (receiver, parameter, return value, function calls, grouping, etc).

Current https://go2goplay.golang.org/p/zBO9K4-yXck

package main

import (
	"fmt"
)

type Stack(type T) struct {
	list []T
}
type Pair(type K, V) struct {
	Key K
	Val V
}

func New(type T)() Stack(T) {
	return Stack(T){list: []T{}}
}
func (s *Stack(T)) Push(v T) {
	s.list = append(s.list, v)
}
func main() {
	a := New(int)()
	fmt.Printf("%#v\n",a)
	b := Stack(Stack(int)){}
	fmt.Printf("%#v\n",b)
	c := Pair(string,int){}
	fmt.Printf("%#v\n",c)
}

Probably more readable syntax:

  • F:T for single generic declaration and usage, eg. Stack:int, BinaryTree:string, Vector:Person
  • F:[T1,T2] for multiple generic declaration and usage or when having constraint or array/slice, eg. Pair:[string,int], HashTable:[string,int], Stack:[T Stringer], Stack:[[3]int]
  • F:[T1:T2] for nested generic usage, eg. Stack:[Queue:int]

So for example, if we want to use Stack that stores string-int Pair, we could use: Stack:[Pair:[string,int]], if we want to use Pair with string key and integer Stack value, we could use: Pair:[string,Stack:int]

The pros:

  • we could always differentiate between function calls (that returns function) and generics by : or :[] symbol, other than just checking whether passed parameter is a datatype or variable/constant identifier. = unambiguous
  • consistent syntax between generic declaration and usage
type Stack:T struct {
	list []T
}
type Pair:[K,V] struct {
	Key K
	Val V
}

func New:T() Stack:T {
	return Stack:T{list: []T{}}
}
func (s *Stack:T) Push(v T) {
	s.list = append(s.list, v)
}
func main() {
	a := New:int()
	fmt.Prinf("%#v\n",a)
	b := Stack:[Stack:int]{}
	fmt.Printf("%#v\n",b)
	c := Pair:[string,int]{}
	fmt.Printf("%#v\n",c)
}
@kokizzu kokizzu changed the title Go 2 generic syntax, replace () with [] Go 2 generic syntax readability: replace () with [] Jun 18, 2020
@mvdan
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@mvdan mvdan commented Jun 18, 2020

This is very explicitly discarded in the draft: https://go.googlesource.com/proposal/+/refs/heads/master/design/go2draft-type-parameters.md#why-not-use-the-syntax

If you want to contest that conclusion, you should directly address that part of the draft, after having read the entire draft carefully.

@mvdan
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@mvdan mvdan commented Jun 18, 2020

Also, from the blog post:

The best way to provide feedback for the language changes will be on the mailing list golang-nuts@googlegroups.com. Mailing lists are imperfect, but they seem like our best option for initial discussion. When writing about the design draft, please put [generics] at the start of the Subject line and to start different threads for different specific topics.

The issue tracker is only for go2go bugs.

@mvdan mvdan closed this Jun 18, 2020
@kokizzu
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@kokizzu kokizzu commented Jun 18, 2020

but this is different, :[] not just []
ok will use mailing list instead

https://groups.google.com/forum/#!topic/golang-nuts/zGQq_I5r2jg

polling: https://www.surveylegend.com/s/2dwe

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