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

C[omp]ute

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

Navier Stokes Incomplete; More on Benford; FBI Claimed Vandalism; Architectural Tessellation; Also: Go, Blake's 7; Delusions of Gender (book); Crypto AG DID work with NSA / GCHQ; UNUMS (Universal Number Format); MOOCs (Massive Open Online Courses); Interesting Looking Game; Euler's Theorem for Polynomials; Weeks 3-6; Reddit Comment; Differential Cryptanalysis For Dummies; Japanese Graphic Design; Books To Be Re-Read; And Today I Learned Bugs Need Clear Examples; Factoring a 67 bit prime in your head; Islamic Geometric Art; Useful Julia Backtraces from Tasks; Nothing, however, is lost with less discomfort than that which, when lost, cannot be missed; Article on Didion; Cost of Living by City; British Slavery; Derrida on Metaphor; African SciFi; Traits in Julia; Alternative Japanese Lit; Pulic Key as Address (Snow); Why Information Grows; The Blindness Of The Chilean Elite; Some Victoriagate Links; This Is Why I Left StackOverflow; New TLS Implementation; Maths for Physicists; How I Am 8; 1000 Word Philosophy; Cyberpunk Reading List; Detailed Discussion of Message Dispatch in ParserCombinator Library for Julia; FizzBuzz in Julia w Dependent Types; kokko - Design Shop in Osaka; Summary of Greece, Currently; LLVM and GPUs; See Also; Schoolgirl Groyps (Maths); Japanese Lit; Another Example - Modular Arithmetic; Music from United; Python 2 and 3 compatible alternative.; Read Agatha Christie for the Plot; A Constructive Look at TempleOS; Music Thread w Many Recommendations; Fixed Version; A Useful Julia Macro To Define Equality And Hash; k3b cdrom access, OpenSuse 13.1; Week 2; From outside, the UK looks less than stellar; Huge Fonts in VirtualBox; Keen - Complex Emergencies; The Fallen of World War II; Some Spanish Fiction; Calling C From Fortran 95; Bjork DJ Set; Z3 Example With Python; Week 1; Useful Guide To Starting With IJulia; UK Election + Media; Review: Reinventing Organizations; Inline Assembly With Julia / LLVM; Against the definition of types; Dumb Crypto Paper; The Search For Quasi-Periodicity...; Is There An Alternative To Processing?; CARDIAC (CARDboard Illustrative Aid to Computation); The Bolivian Case Against Chile At The Hague; Clear, Cogent Economic Arguments For Immigration; A Program To Say If I Am Working; Decent Cards For Ill People; New Photo; Luksic And Barrick Gold; President Bachelet's Speech; Baltimore Primer; libxml2 Parsing Stream; configure.ac Recipe For Library Path; The Davalos Affair For Idiots; Not The Onion: Google Fireside Chat w Kissinger; Bicycle Wheels, Inertia, and Energy; Another Tax Fraud; Google's Borg; A Verion That Redirects To Local HTTP Server; Spanish Accents For Idiots; Aluminium Cans; Advice on Spray Painting; Female View of Online Chat From a Male; UX Reading List; S4 Subgroups - Geometric Interpretation; Fucking Email; The SQM Affair For Idiots; Using Kolmogorov Complexity; Oblique Strategies in bash; Curses Tools

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

New Parser in Python

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

Date: Mon, 12 Jan 2009 00:54:55 -0300 (CLST)

Not ready for release yet, but I've just got a new parser, written in
Python, to the point where it's useful.

It includes full backtracing (parse forests etc), the (untested) ability
to 'automatically' control resource use (think 'maximum backtrace stack')
and enough syntactic sugar to rot your teeth :o)

This test:


from logging import basicConfig, DEBUG
from unittest import TestCase

from lepl.match import *
from lepl.node import Node


class NodeTest(TestCase):


  def test_node(self):
    basicConfig(level=DEBUG)

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

    expression  = Delayed()
    number      = Digit()[1:,...]                   > 'number'
    term        = (number | '(' / expression / ')') > Term
    muldiv      = Any('*/')                         > 'operator'
    factor      = (term / (muldiv / term)[0:])      > Factor
    addsub      = Any('+-')                         > 'operator'
    expression += (factor / (addsub / factor)[0:])  > Expression

    (ast, _) = next(expression.match_string('1 + 2 * (3 + 4 - 5)'))
    print(ast[0])
    (ast, _) = next(expression('1 + 2 * (3 + 4 - 5)'))
    print(ast[0])


Prints the following (twice):

Expression
 +- Factor
 |   +- Term
 |   |   `- number=1
 |   `- ' '
 +- operator=+
 +- ' '
 `- Factor
     +- Term
     |   `- number=2
     +- ' '
     +- operator=*
     +- ' '
     `- Term
         +- '('
         +- Expression
         |   +- Factor
         |   |   +- Term
         |   |   |   `- number=3
         |   |   `- ' '
         |   +- operator=+
         |   +- ' '
         |   +- Factor
         |   |   +- Term
         |   |   |   `- number=4
         |   |   `- ' '
         |   +- operator=-
         |   +- ' '
         |   `- Factor
         |       `- Term
         |           `- number=5
         `- ')'

Andrew

Parsing Credits

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

Date: Mon, 12 Jan 2009 00:58:24 -0300 (CLST)

I should have added that this copies lots of good ideas from both
pyparsing - http://pyparsing.wikispaces.com/ - and (more so) "Pattern
Matching In Python" http://www.wilmott.ca/python/patternmatching.html

Andrew

Syntax

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

Date: Mon, 12 Jan 2009 01:11:39 -0300 (CLST)

A quick explanation of the syntax:

This allows forward references to 'expression', which will be defined later.

    expression  = Delayed()

This defines 'number' as one or more digits, specified via '[1:]', and
combines the digits into a single string, specified via '[...]'.  The
result is then associated with the tag 'number'.

    number      = Digit()[1:,...]                   > 'number'

This defines term as either 'number' or (with backtracing) a bracketed
expression.  The strings are automatically promoted to literal matches and
the '/' indicate that there are optional spaces between the matchers ('//'
for required space).  The result is used to construct a Term instance,
which is a subclass of Node (and which will automatically construct
attributes for the contents).

    term        = (number | '(' / expression / ')') > Term

Define 'muldiv' to be either '*' or '/' and tag the result.

    muldiv      = Any('*/')                         > 'operator'

Hopefully this is becoming obvious.  The '[0:]' here means '0 or more'
instances of 'muldiv', optional space, and 'term'.

    factor      = (term / (muldiv / term)[0:])      > Factor

Nothing new here.

    addsub      = Any('+-')                         > 'operator'

This defines the 'Delayed' matcher introduced earlier (it was introduced
so that we could reference it in 'term', even though we cannot define it
until later).

    expression += (factor / (addsub / factor)[0:])  > Expression

Not sure if it's obvious, but one major aim has been to try to combine the
best of both OO and functional programming, in what I feel is a very
'Pythonic' way.

Andrew

With Bactracking

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

Date: Mon, 12 Jan 2009 01:25:59 -0300 (CLST)

Changing the spec slightly to:

  expression  = Delayed()
  number      = Digit()[1:,...]                   > 'number'
  term        = (number | '(' / expression / ')') > Term
  muldiv      = Any('*/')                         > 'operator'
  factor      = (term / (muldiv / term)[0:])      > Factor
  addsub      = Any('+-')                         > 'operator'
  expression += Drop(Any()[0:]) & \
                (factor / (addsub / factor)[0:])  > Expression

And using:

  for (ast, _) in expression('1 + 2 * (3 + 4 - 5)'):
    print(ast[0])

Gives:

Expression
 `- Factor
     `- Term
         `- number '5'
Expression
 +- Factor
 |   +- Term
 |   |   `- number '4'
 |   `- ' '
 +- operator '-'
 +- ' '
 `- Factor
     `- Term
         `- number '5'
Expression
 `- Factor
     +- Term
     |   `- number '4'
     `- ' '
Expression
 +- Factor
 |   `- Term
 |       `- number '4'
 +- ' '
 +- operator '-'
 +- ' '
 `- Factor
     `- Term
         `- number '5'
Expression
 +- Factor
 |   `- Term
 |       `- number '4'
 `- ' '
Expression
 `- Factor
     `- Term
         `- number '4'
Expression
 +- Factor
 |   +- Term
 |   |   `- number '3'
 |   `- ' '
 +- operator '+'
 +- ' '
 +- Factor
 |   +- Term
 |   |   `- number '4'
 |   `- ' '
 +- operator '-'
 +- ' '
 `- Factor
     `- Term
         `- number '5'
Expression
 +- Factor
 |   +- Term
 |   |   `- number '3'
 |   `- ' '
 +- operator '+'
 +- ' '
 `- Factor
     +- Term
     |   `- number '4'
     `- ' '
Expression
 +- Factor
 |   +- Term
 |   |   `- number '3'
 |   `- ' '
 +- operator '+'
 +- ' '
 `- Factor
     `- Term
         `- number '4'
Expression
 `- Factor
     +- Term
     |   `- number '3'
     `- ' '
Expression
 +- Factor
 |   `- Term
 |       `- number '3'
 +- ' '
 +- operator '+'
 +- ' '
 +- Factor
 |   +- Term
 |   |   `- number '4'
 |   `- ' '
 +- operator '-'
 +- ' '
 `- Factor
     `- Term
         `- number '5'
Expression
 +- Factor
 |   `- Term
 |       `- number '3'
 +- ' '
 +- operator '+'
 +- ' '
 `- Factor
     +- Term
     |   `- number '4'
     `- ' '
Expression
 +- Factor
 |   `- Term
 |       `- number '3'
 +- ' '
 +- operator '+'
 +- ' '
 `- Factor
     `- Term
         `- number '4'
Expression
 +- Factor
 |   `- Term
 |       `- number '3'
 `- ' '
Expression
 `- Factor
     `- Term
         `- number '3'
Expression
 `- Factor
     `- Term
         +- '('
         +- Expression
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 `- Factor
     `- Term
         +- '('
         +- Expression
         |   +- Factor
         |   |   +- Term
         |   |   |   `- number '4'
         |   |   `- ' '
         |   +- operator '-'
         |   +- ' '
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 `- Factor
     `- Term
         +- '('
         +- Expression
         |   +- Factor
         |   |   `- Term
         |   |       `- number '4'
         |   +- ' '
         |   +- operator '-'
         |   +- ' '
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 `- Factor
     `- Term
         +- '('
         +- Expression
         |   +- Factor
         |   |   +- Term
         |   |   |   `- number '3'
         |   |   `- ' '
         |   +- operator '+'
         |   +- ' '
         |   +- Factor
         |   |   +- Term
         |   |   |   `- number '4'
         |   |   `- ' '
         |   +- operator '-'
         |   +- ' '
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 `- Factor
     `- Term
         +- '('
         +- Expression
         |   +- Factor
         |   |   `- Term
         |   |       `- number '3'
         |   +- ' '
         |   +- operator '+'
         |   +- ' '
         |   +- Factor
         |   |   +- Term
         |   |   |   `- number '4'
         |   |   `- ' '
         |   +- operator '-'
         |   +- ' '
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 `- Factor
     +- Term
     |   `- number '2'
     +- ' '
     +- operator '*'
     +- ' '
     `- Term
         +- '('
         +- Expression
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 `- Factor
     +- Term
     |   `- number '2'
     +- ' '
     +- operator '*'
     +- ' '
     `- Term
         +- '('
         +- Expression
         |   +- Factor
         |   |   +- Term
         |   |   |   `- number '4'
         |   |   `- ' '
         |   +- operator '-'
         |   +- ' '
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 `- Factor
     +- Term
     |   `- number '2'
     +- ' '
     +- operator '*'
     +- ' '
     `- Term
         +- '('
         +- Expression
         |   +- Factor
         |   |   `- Term
         |   |       `- number '4'
         |   +- ' '
         |   +- operator '-'
         |   +- ' '
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 `- Factor
     +- Term
     |   `- number '2'
     +- ' '
     +- operator '*'
     +- ' '
     `- Term
         +- '('
         +- Expression
         |   +- Factor
         |   |   +- Term
         |   |   |   `- number '3'
         |   |   `- ' '
         |   +- operator '+'
         |   +- ' '
         |   +- Factor
         |   |   +- Term
         |   |   |   `- number '4'
         |   |   `- ' '
         |   +- operator '-'
         |   +- ' '
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 `- Factor
     +- Term
     |   `- number '2'
     +- ' '
     +- operator '*'
     +- ' '
     `- Term
         +- '('
         +- Expression
         |   +- Factor
         |   |   `- Term
         |   |       `- number '3'
         |   +- ' '
         |   +- operator '+'
         |   +- ' '
         |   +- Factor
         |   |   +- Term
         |   |   |   `- number '4'
         |   |   `- ' '
         |   +- operator '-'
         |   +- ' '
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 `- Factor
     +- Term
     |   `- number '2'
     `- ' '
Expression
 +- Factor
 |   `- Term
 |       `- number '2'
 `- ' '
Expression
 `- Factor
     `- Term
         `- number '2'
Expression
 +- Factor
 |   +- Term
 |   |   `- number '1'
 |   `- ' '
 +- operator '+'
 +- ' '
 `- Factor
     +- Term
     |   `- number '2'
     +- ' '
     +- operator '*'
     +- ' '
     `- Term
         +- '('
         +- Expression
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 +- Factor
 |   +- Term
 |   |   `- number '1'
 |   `- ' '
 +- operator '+'
 +- ' '
 `- Factor
     +- Term
     |   `- number '2'
     +- ' '
     +- operator '*'
     +- ' '
     `- Term
         +- '('
         +- Expression
         |   +- Factor
         |   |   +- Term
         |   |   |   `- number '4'
         |   |   `- ' '
         |   +- operator '-'
         |   +- ' '
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 +- Factor
 |   +- Term
 |   |   `- number '1'
 |   `- ' '
 +- operator '+'
 +- ' '
 `- Factor
     +- Term
     |   `- number '2'
     +- ' '
     +- operator '*'
     +- ' '
     `- Term
         +- '('
         +- Expression
         |   +- Factor
         |   |   `- Term
         |   |       `- number '4'
         |   +- ' '
         |   +- operator '-'
         |   +- ' '
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 +- Factor
 |   +- Term
 |   |   `- number '1'
 |   `- ' '
 +- operator '+'
 +- ' '
 `- Factor
     +- Term
     |   `- number '2'
     +- ' '
     +- operator '*'
     +- ' '
     `- Term
         +- '('
         +- Expression
         |   +- Factor
         |   |   +- Term
         |   |   |   `- number '3'
         |   |   `- ' '
         |   +- operator '+'
         |   +- ' '
         |   +- Factor
         |   |   +- Term
         |   |   |   `- number '4'
         |   |   `- ' '
         |   +- operator '-'
         |   +- ' '
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 +- Factor
 |   +- Term
 |   |   `- number '1'
 |   `- ' '
 +- operator '+'
 +- ' '
 `- Factor
     +- Term
     |   `- number '2'
     +- ' '
     +- operator '*'
     +- ' '
     `- Term
         +- '('
         +- Expression
         |   +- Factor
         |   |   `- Term
         |   |       `- number '3'
         |   +- ' '
         |   +- operator '+'
         |   +- ' '
         |   +- Factor
         |   |   +- Term
         |   |   |   `- number '4'
         |   |   `- ' '
         |   +- operator '-'
         |   +- ' '
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 +- Factor
 |   +- Term
 |   |   `- number '1'
 |   `- ' '
 +- operator '+'
 +- ' '
 `- Factor
     +- Term
     |   `- number '2'
     `- ' '
Expression
 +- Factor
 |   +- Term
 |   |   `- number '1'
 |   `- ' '
 +- operator '+'
 +- ' '
 `- Factor
     `- Term
         `- number '2'
Expression
 `- Factor
     +- Term
     |   `- number '1'
     `- ' '
Expression
 +- Factor
 |   `- Term
 |       `- number '1'
 +- ' '
 +- operator '+'
 +- ' '
 `- Factor
     +- Term
     |   `- number '2'
     +- ' '
     +- operator '*'
     +- ' '
     `- Term
         +- '('
         +- Expression
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 +- Factor
 |   `- Term
 |       `- number '1'
 +- ' '
 +- operator '+'
 +- ' '
 `- Factor
     +- Term
     |   `- number '2'
     +- ' '
     +- operator '*'
     +- ' '
     `- Term
         +- '('
         +- Expression
         |   +- Factor
         |   |   +- Term
         |   |   |   `- number '4'
         |   |   `- ' '
         |   +- operator '-'
         |   +- ' '
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 +- Factor
 |   `- Term
 |       `- number '1'
 +- ' '
 +- operator '+'
 +- ' '
 `- Factor
     +- Term
     |   `- number '2'
     +- ' '
     +- operator '*'
     +- ' '
     `- Term
         +- '('
         +- Expression
         |   +- Factor
         |   |   `- Term
         |   |       `- number '4'
         |   +- ' '
         |   +- operator '-'
         |   +- ' '
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 +- Factor
 |   `- Term
 |       `- number '1'
 +- ' '
 +- operator '+'
 +- ' '
 `- Factor
     +- Term
     |   `- number '2'
     +- ' '
     +- operator '*'
     +- ' '
     `- Term
         +- '('
         +- Expression
         |   +- Factor
         |   |   +- Term
         |   |   |   `- number '3'
         |   |   `- ' '
         |   +- operator '+'
         |   +- ' '
         |   +- Factor
         |   |   +- Term
         |   |   |   `- number '4'
         |   |   `- ' '
         |   +- operator '-'
         |   +- ' '
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 +- Factor
 |   `- Term
 |       `- number '1'
 +- ' '
 +- operator '+'
 +- ' '
 `- Factor
     +- Term
     |   `- number '2'
     +- ' '
     +- operator '*'
     +- ' '
     `- Term
         +- '('
         +- Expression
         |   +- Factor
         |   |   `- Term
         |   |       `- number '3'
         |   +- ' '
         |   +- operator '+'
         |   +- ' '
         |   +- Factor
         |   |   +- Term
         |   |   |   `- number '4'
         |   |   `- ' '
         |   +- operator '-'
         |   +- ' '
         |   `- Factor
         |       `- Term
         |           `- number '5'
         `- ')'
Expression
 +- Factor
 |   `- Term
 |       `- number '1'
 +- ' '
 +- operator '+'
 +- ' '
 `- Factor
     +- Term
     |   `- number '2'
     `- ' '
Expression
 +- Factor
 |   `- Term
 |       `- number '1'
 +- ' '
 +- operator '+'
 +- ' '
 `- Factor
     `- Term
         `- number '2'
Expression
 +- Factor
 |   `- Term
 |       `- number '1'
 `- ' '
Expression
 `- Factor
     `- Term
         `- number '1'

Comment on this post