Re: associative arrays

> On Nov 2, 2021, at 3:57 PM, Ashley Sheridan <ash@ashleysheridan.co.uk> wrote: > > > On 02/11/2021 21:21, JEFFRY KILLEN wrote: >> >>> On Nov 2, 2021, at 1:03 PM, Tedd Sperling <tedd.sperling@gmail.com> wrote: >>> >>> >>> >>>> On Nov 2, 2021, at 2:25 PM, Christoph M. Becker <cmbecker69@gmx.de> wrote: >>>> >>>> On 02.11.2021 at 07:24, JEFFRY KILLEN wrote: >>>>> Hello: >>>>> >>>>> I have been programming php and javascript for some time. >>>>> I have not come on a way to navigate upward in javascript >>>>> objects (it does not have associative arrays but objects are >>>>> often used in the same way associative arrays are used) >>>>> >>>>> To create a metaphor: it is like a squirrel jumps from another tree and lands >>>>> on a branch. It >>>>> can find its way to the trunk and to the ground. >>>> The squirrel doesn't ask the branch how to get to the trunk or to the >>>> ground, though. Instead, it remembers its way so far. :) >>>> >>>> -- >>>> Christoph M. Becker >>> Not quite, a better analogy would be the squirrel doesn’t know on what branch his >>> father found his mother. >>> >>> More specifically, an array inside another array doesn’t know it’s inside another >>> array. In fact, it’s simply a memory address that can only be located via an index inside another >>> array, which is yet another memory address. Ask any memory address where it is and it can answer >>> you, but it can’t offer much more information other than what it is — after all, it’s just a >>> memory address. >>> >>> If you want data to tell you what data proceeded it, then look into a double >>> linked-list. That might solve your problem. >>> >>> Cheers, >>> >>> Tedd >>> >>> Tedd Sperling >>> tedd.sperling@gmail.com >> Yes, the squirrel analogy is a weak analogy. But like a file system, the array is a tree >> structure, as I >> understand it. Code or user can navigate around the file system paths using '..', >> which refers to the >> parent directory of the current directory. >> >> But where memory is concerned, in order to get to a particular branch, or object/array >> property >> the path has to already be known. Or recursive processing can hunt for a property and save >> what it finds for future reference. But that is the rub. It will have to save the property >> chain as >> a string. Then future reference has to use eval on the string to get the value or >> properties stored >> there. At least that is true for javascript and working with both, I am concerned with >> being able >> to translate from one to another. I presume that php works in a similar way: IE nested >> properties >> can be found with recusive search. But the chain of properties would have to saved as a >> string >> for future reference. And eval would have to be used to get to the value(s) and/or sibling >> properties. >> represented by the string. >> >> Or is there another way? >> >> I appreciate this exchange. Thank you >> JK > > You have your understanding of arrays wrong. An array is nothing like a tree structure, no > matter how you think of them. A file tree would use a doubly linked list, as Tedd pointed out. These > are effectively lists of objects, each one references it's parents, children, or siblings, > within the list. > > Arrays are dumb lists, each element contains no reference to what went before, or after, and > has no understanding or concept of a "parent". They're so dumb that internally PHP > uses an internal pointer when traversing an array, and you can use functions like current(), next(), > and reset(), to manage that pointer. > > If you need that kind of capability, then you need objects, not arrays. > > -- > Ashley Sheridan > https://www.ashleysheridan.co.uk Thank you for your guidance and suggestions; JK