Hitting the Tail Recursion wall

On 01/04/19 15:49, Andreas Mixich wrote: > I think, I am finding it... > > I replaced the first expression with > > `prof:dump(concat("in: ", $path, " out: ", > string-join(array:flatten($out)))),` > > and this gives me more info. So I may be able to solve this alone. >

Marco Lettere wrote onm 01.04.2019 at 18:01: > declare function local:topath($path){ let $pathseg := tokenize($path, > "/") return fold-left($pathseg, (), function($out, $segment){ > if($segment = "." or $segment = "") then $out else if($segment = > "..") then $out[position() lt count($out)] else ($out, > $segment) })}; local:topath("/a/b/c/../../../g")

On 01/04/19 22:02, Andreas Mixich wrote: > Marco Lettere wrote onm 01.04.2019 at 18:01: > >> declare function local:topath($path){ let $pathseg := tokenize($path, >> "/") return fold-left($pathseg, (), function($out, $segment){ >> if($segment = "." or $segment = "") then $out else if($segment = >> "..") then $out[position() lt count($out)] else ($out, >> $segment) })}; local:topath("/a/b/c/../../../g") > Beautiful and very close, except for a minor caveat: the "/" are needed, > to reconstruct the absolute path-part from the relative. > I played around and tried to place some "/" to your function, but all > variants placed some "/" wrong or twice. > > Last but not least: You asked for the use case, which is described on > https://tools.ietf.org/html/rfc3986#section-5.2.4 (note also the > sequences shown after the description of the steps) > > > 5.2.4 <https://tools.ietf.org/html/rfc3986#section-5.2.4>. > Remove Dot Segments > > > > The pseudocode also refers to a "remove_dot_segments" routine for > interpreting and removing the special "." and ".." complete path > segments from a referenced path. This is done after the path is > extracted from a reference, whether or not the path was relative, in > order to remove any invalid or extraneous dot-segments prior to > forming the target URI. Although there are many ways to accomplish > this removal process, we describe a simple method using two string > buffers. > > 1. The input buffer is initialized with the now-appended path > components and the output buffer is initialized to the empty > string. > > 2. While the input buffer is not empty, loop as follows: > > A. If the input buffer begins with a prefix of "../" or "./", > then remove that prefix from the input buffer; otherwise, > > B. if the input buffer begins with a prefix of "/./" or "/.", > where "." is a complete path segment, then replace that > prefix with "/" in the input buffer; otherwise, > > C. if the input buffer begins with a prefix of "/../" or "/..", > where ".." is a complete path segment, then replace that > prefix with "/" in the input buffer and remove the last > segment and its preceding "/" (if any) from the output > buffer; otherwise, > > D. if the input buffer consists only of "." or "..", then remove > that from the input buffer; otherwise, > > E. move the first path segment in the input buffer to the end of > the output buffer, including the initial "/" character (if > any) and any subsequent characters up to, but not including, > the next "/" character or the end of the input buffer. > > 3. Finally, the output buffer is returned as the result of > remove_dot_segments. > > Note that dot-segments are intended for use in URI references to > express an identifier relative to the hierarchy of names in the base > URI. The remove_dot_segments algorithm respects that hierarchy by > removing extra dot-segments rather than treat them as an error or > leaving them to be misinterpreted by dereference implementations. > > The following illustrates how the above steps are applied for two > examples of merged paths, showing the state of the two buffers after > each step. > > STEP OUTPUT BUFFER INPUT BUFFER > > 1 : /a/b/c/./../../g > 2E: /a /b/c/./../../g > 2E: /a/b /c/./../../g > 2E: /a/b/c /./../../g > 2B: /a/b/c /../../g > 2C: /a/b /../g > 2C: /a /g > 2E: /a/g > > STEP OUTPUT BUFFER INPUT BUFFER > > 1 <https://tools.ietf.org/html/rfc3986#section-1> : mid/content=5/../6 > 2E: mid /content=5/../6 > 2E: mid/content=5 /../6 > 2C: mid /6 > 2E: mid/6 > > > > >