Andrew Cooke | Contents | Latest | RSS | Previous | Next


Welcome to my blog, which was once a mailing list of the same name and is still generated by mail. Please reply via the "comment" links.

Always interested in offers/projects/new ideas. Eclectic experience in fields like: numerical computing; Python web; Java enterprise; functional languages; GPGPU; SQL databases; etc. Based in Santiago, Chile; telecommute worldwide. CV; email.

Personal Projects

Choochoo Training Diary

Last 100 entries

[Programming] React Leaflet; AliExpress Independent Sellers; Applebaum - Twilight of Democracy; [Politics] Back + US Elections; [Programming,Exercise] Simple Timer Script; [News] 2019: The year revolt went global; [Politics] The world's most-surveilled cities; [Bike] Hope Freehub; [Restaurant] Mama Chau's (Chinese, Providencia); [Politics] Brexit Podcast; [Diary] Pneumonia; [Politics] Britain's Reichstag Fire moment; install cairo; [Programming] GCC Sanitizer Flags; [GPU, Programming] Per-Thread Program Counters; My Bike Accident - Looking Back One Year; [Python] Geographic heights are incredibly easy!; [Cooking] Cookie Recipe; Efficient, Simple, Directed Maximisation of Noisy Function; And for argparse; Bash Completion in Python; [Computing] Configuring Github Jekyll Locally; [Maths, Link] The Napkin Project; You can Masquerade in Firewalld; [Bike] Servicing Budget (Spring) Forks; [Crypto] CIA Internet Comms Failure; [Python] Cute Rate Limiting API; [Causality] Judea Pearl Lecture; [Security, Computing] Chinese Hardware Hack Of Supermicro Boards; SQLAlchemy Joined Table Inheritance and Delete Cascade; [Translation] The Club; [Computing] Super Potato Bruh; [Computing] Extending Jupyter; Further HRM Details; [Computing, Bike] Activities in ch2; [Books, Link] Modern Japanese Lit; What ended up there; [Link, Book] Logic Book; Update - Garmin Express / Connect; Garmin Forerunner 35 v 230; [Link, Politics, Internet] Government Trolls; [Link, Politics] Why identity politics benefits the right more than the left; SSH Forwarding; A Specification For Repeating Events; A Fight for the Soul of Science; [Science, Book, Link] Lost In Math; OpenSuse Leap 15 Network Fixes; Update; [Book] Galileo's Middle Finger; [Bike] Chinese Carbon Rims; [Bike] Servicing Shimano XT Front Hub HB-M8010; [Bike] Aliexpress Cycling Tops; [Computing] Change to ssh handling of multiple identities?; [Bike] Endura Hummvee Lite II; [Computing] Marble Based Logic; [Link, Politics] Sanity Check For Nuclear Launch; [Link, Science] Entropy and Life; [Link, Bike] Cheap Cycling Jerseys; [Link, Music] Music To Steal 2017; [Link, Future] Simulated Brain Drives Robot; [Link, Computing] Learned Index Structures; Solo Air Equalization; Update: Higher Pressures; Psychology; [Bike] Exercise And Fuel; Continental Race King 2.2; Removing Lowers; Mnesiacs; [Maths, Link] Dividing By Zero; [Book, Review] Ray Monk - Ludwig Wittgenstein: The Duty Of Genius; [Link, Bike, Computing] Evolving Lacing Patterns; [Jam] Strawberry and Orange Jam; [Chile, Privacy] Biometric Check During Mail Delivery; [Link, Chile, Spanish] Article on the Chilean Drought; [Bike] Extended Gear Ratios, Shimano XT M8000 (24/36 Chainring); [Link, Politics, USA] The Future Of American Democracy; Mass Hysteria; [Review, Books, Links] Kazuo Ishiguro - Never Let Me Go; [Link, Books] David Mitchell's Favourite Japanese Fiction; [Link, Bike] Rear Suspension Geometry; [Link, Cycling, Art] Strava Artwork; [Link, Computing] Useful gcc flags; [Link] Voynich Manuscript Decoded; [Bike] Notes on Servicing Suspension Forks; [Links, Computing] Snap, Flatpack, Appimage; [Link, Computing] Oracle is leaving Java (to die); [Link, Politics] Cubans + Ultrasonics; [Book, Link] Laurent Binet; VirtualBox; [Book, Link] No One's Ways; [Link] The Biggest Problem For Cyclists Is Bad Driving; [Computing] Doxygen, Sphinx, Breathe; [Admin] Brokw Recent Permalinks; [Bike, Chile] Buying Bearings in Santiago; [Computing, Opensuse] Upgrading to 42.3; [Link, Physics] First Support for a Physics Theory of Life; [Link, Bike] Peruvian Frame Maker; [Link] Awesome Game Theory Tit-For-Tat Thing; [Food, Review] La Fabbrica - Good Italian Food In Santiago; [Link, Programming] MySQL UTF8 Broken; [Link, Books] Latin American Authors

© 2006-2017 Andrew Cooke (site) / post authors (content).

Stream to Tree

From: "andrew cooke" <andrew@...>

Date: Mon, 25 Aug 2008 15:30:09 -0400 (CLT)

I just had to convert a stream (list) of values to a tree.  Each list item
had a "depth" that could be one more than the previous value (a child),
the same (a sibling) or a smaller value (some ancestor).

This seems trivial, I know, but it took me some thinking.  On the other
hand the final code is quite simple (and uses an accumulator to keep
sibling order), so here it is for future reference.  Note that some slight
oddities are necessary because of Python's strange list (more like arrays)
data type.

    def build_tree(lines, level=0, acc=[]):
        while lines and lines[0][0] == level:
            (depth, key, text, description) = lines[0]
            (lines, children) = build_tree(lines[1:], level+1, [])
            acc.append([key, text, description, children])
        return (lines, acc)

The each entry in the list has the structure (depth, key, text,
description) where depth is as described earlier.  So the lines[0][0] is a
peek into the next depth.  And the resulting tree nodes have the form
(key, text, description, children).  There's nothing special about key,
text and description - that's just the particulars of the data I was
working with.

It's quite succinct, IMHO.  I assume that it's some kind of banana
(catamorphism) or related gubbins that I can no longer remember and never
completely understood anyway...


Comment on this post