| Andrew Cooke | Contents | Latest | RSS | Twitter | 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

Lepl parser for Python.

Colorless Green.

Photography around Santiago.

SVG experiment.

Professional Portfolio

Calibration of seismometers.

Data access via web services.

Cache rewrite.

Extending OpenSSH.

C-ORM: docs, API.

Last 100 entries

Consciousness From Max Entropy; Democrats; Harvard Will Fix Black Poverty; Modelling Bicycle Wheels; Amusing Polling Outlier; If Labour keeps telling working class people...; Populism and Choice; Books on Defeat; Enrique Ferrari - Argentine Author; Transcript of German Scientists on Learning of Hiroshima; Calvert Journal; Telephone System Quotes for Cat Soft LLC; Owen Jones on Twitter; Telephone System Quotes for Cat Soft LLC; Possible Japanese Authors; Complex American Literature; Chutney v5; Weird Componentized Virus; Interesting Argentinian Author - Antonio Di Benedetto; Useful Thread on MetaPhysics; RAND on fighting online anarchy (2001); Now Is Cat Soft LLC's Chance To Save Up To 32% On Mail; NSA Hacked; Call Center Services for Cat Soft LLC; Very Good LRB Article on Brexit; Nussbaum on Anger; Credit Card Processing for Cat Soft LLC; Discover new movies on demand in our online cinema; Tasting; Credit Card Processing for Cat Soft LLC; Apple + Kiwi Jam; Hit Me; Increase Efficiency with GPS Vehicle Tracking for Cat Soft LLC; Sudoku - CSP + Chaos; Recycling Electronics In Santiago; Vector Displays in OpenGL; Call Center Services for Cat Soft LLC; And Anti-Aliased; OpenGL - Render via Intermediate Texture; And Garmin Connect; Using Garmin Forerunner 230 With Linux; Payroll Service Quotes for Cat Soft LLC; (Beating Dead Horse) StackOverflow; Current State of Justice in China; Now Is Cat Soft LLC's Chance To Save Up To 32% On Mail; Axiom of Determinacy; Ewww; Fee Chaos Book; Course on Differential Geometry; Increase Efficiency with GPS Vehicle Tracking for Cat Soft LLC; Okay, but...; Sparse Matrices, Deep Learning; Sounds Bad; Applebaum Rape; Tomato Chutney v4; Have to add...; Culturally Liberal and Nothing More; Weird Finite / Infinite Result; Your diamond is a beaten up mess; Maths Books; Good Bike Route from Providencia / Las Condes to Panul\; Iain Pears (Author of Complex Plots); Plum Jam; Excellent; More Recently; For a moment I forgot StackOverflow sucked; A Few Weeks On...; Chilean Book Recommendations; How To Write Shared Libraries; Jenny Erpenbeck (Author); Dijkstra, Coins, Tables; Python libraries error on OpenSuse; Deserving Trump; And Smugness; McCloskey Economics Trilogy; cmocka - Mocks for C; Concept Creep (Americans); Futhark - OpenCL Language; Moved / Gone; Fan and USB issues; Burgers in Santiago; The Origin of Icosahedral Symmetry in Viruses; autoenum on PyPI; Jars Explains; Tomato Chutney v3; REST; US Elections and Gender: 24 Point Swing; PPPoE on OpenSuse Leap 42.1; SuperMicro X10SDV-TLN4F/F with Opensuse Leap 42.1; Big Data AI Could Be Very Bad Indeed....; Cornering; Postcapitalism (Paul Mason); Black Science Fiction; Git is not a CDN; Mining of Massive Data Sets; Rachel Kaadzi Ghansah; How great republics meet their end; Raspberry, Strawberry and Banana Jam; Interesting Dead Areas of Math; Later Taste; For Sale

© 2006-2015 Andrew Cooke (site) / post authors (content).

Initial Tokenizer Results for LEPL

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

Date: Sun, 19 Apr 2009 08:56:06 -0400 (CLT)

Spent yesterday travelling and, in an attempt to get work out of my head,
hacked on LEPL's tokenizer support.

I never completed a comment discussing the syntax, but the following shows
how it integrates nicely into what is already there.  Note, for example,
the use of Float() inside Token().  This uses the "compile to regexp"
support I added earlier to convert the Float() matcher to a regexp that's
then used by the tokenizer.

Also, note how handling of spaces becomes much simpler with a lexer
because it's no longer explicit in the grammar (well, only in the token

Another feature, hardly exploited below, is that you can match inside a
token.  For example symbol('(') requires that (i) a symbol token exist and
(ii) that it matches '(' (whether the match requires the entire token or
not is currently undefined - I think it would be best if it does by

So, here's the test code and output:

  class Call(Node): pass
  class Term(Node): pass
  class Factor(Node): pass
  class Expression(Node): pass

  value  = Token(Float())                       > 'number'
  name   = Token('[a-z]+')
  symbol = Token('[^a-zA-Z0-9\\. ]')

  expr    = Delayed()
  open    = symbol('(')
  close   = symbol(')')
  funcn   = name                                > 'name'
  call    = funcn & open & expr & close         > Call
  term    = call | value | open & expr & close  > Term
  muldiv  = symbol(Any('*/'))                   > 'operator'
  factor  = term & (muldiv & term)[:]           > Factor
  addsub  = symbol(Any('+-'))                   > 'operator'
  expr   += factor & (addsub & factor)[:]       > Expression
  line    = expr & Eos()

  parser = line.null_parser(
  parser('1 + 2*sin(3+ 4)')[0]

 +- Factor
 |   `- Term
 |       `- number '1'
 +- operator '+'
 `- Factor
     +- Term
     |   `- number '2'
     +- operator '*'
     `- Term
         `- Call
             +- name 'sin'
             +- '('
             +- Expression
             |   +- Factor
             |   |   `- Term
             |   |       `- number '3'
             |   +- operator '+'
             |   `- Factor
             |       `- Term
             |           `- number '4'
             `- ')'


Comment on this post