Golang go/ast.CommentMap.Comments() and Filter() functions example

package go/ast

go/ast.CommentMap.Comments()

Comments returns the list of comment groups in the comment map. The result is sorted is source order.

go/ast.CommentMap.Filter()

Filter returns a new comment map consisting of only those entries of cmap for which a corresponding node exists in the AST specified by node.

Golang go/ast.CommentMap.Comments() and Filter() functions example

Example( taken from http://golang.org/pkg/go/ast/#CommentMap )

  // Create the AST by parsing src.
  fset := token.NewFileSet() // positions are relative to fset
  f, err := parser.ParseFile(fset, "src.go", src, parser.ParseComments)
  if err != nil {
 panic(err)
  }

  // Create an ast.CommentMap from the ast.File's comments.
  // This helps keeping the association between comments
  // and AST nodes.
  cmap := ast.NewCommentMap(fset, f, f.Comments) // <-- here

go/ast.CommentMap.Filter() :

 func packageExports(fset *token.FileSet, pkg *ast.Package) {
  for _, src := range pkg.Files {
 cmap := ast.NewCommentMap(fset, src, src.Comments)
 ast.FileExports(src)
 src.Comments = cmap.Filter(src).Comments()
  }
 }

References :

http://golang.org/pkg/go/ast/#CommentMap.Comments

http://golang.org/pkg/go/ast/#CommentMap.Filter