proposal: go/ast: add DepthFirst iterator #66339
Comments
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Change https://go.dev/cl/570680 mentions this issue: |
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For the curious, it adds 10-15% to the cost of a trivial traversal. package ast_test
import (
"go/ast"
"go/parser"
"go/token"
"testing"
)
var file *ast.File
func init() {
file, _ = parser.ParseFile(token.NewFileSet(), "ast.go", nil, 0)
}
const k = 2
func BenchmarkInspect(b *testing.B) {
total := 0
for range b.N {
var nodes []ast.Node
ast.Inspect(file, func(n ast.Node) bool {
if n != nil {
total++
if total%k == 0 {
nodes = append(nodes, n)
}
}
return true
})
}
}
func BenchmarkRange(b *testing.B) {
total := 0
for range b.N {
var nodes []ast.Node
for n := range ast.DepthFirst(file) {
total++
if total%k == 0 {
nodes = append(nodes, n)
}
}
}
} |
rsc
changed the title
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This proposal has been added to the active column of the proposals project |
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The name DepthFirst doesn't indicate whether its Preorder or Postorder. It sounds like we should call it Preorder. |
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Have all remaining concerns about this proposal been addressed? The proposal is to add: |
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Proposal Details
Programs that use
go/astoften need to make traversals over the tree to find all nodes of a given type (or types), or to search for a specific node. The existingast.Inspectfunction allows them to do this, but it can impose a significant syntactic overhead. This example shows a use of Inspect to print the first interesting node, aborting the traversal once the node is found:We propose to add this function to go/ast:
which would allow the previous example to be simplified to:
cc @findleyr @griesemer
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