/Demo/threads/squasher.py
http://unladen-swallow.googlecode.com/ · Python · 105 lines · 62 code · 13 blank · 30 comment · 14 complexity · 4b8a7c84cac5c00f9742d5cf871b38e0 MD5 · raw file
- # Coroutine example: general coroutine transfers
- #
- # The program is a variation of a Simula 67 program due to Dahl & Hoare,
- # (Dahl/Dijkstra/Hoare, Structured Programming; Academic Press, 1972)
- # who in turn credit the original example to Conway.
- #
- # We have a number of input lines, terminated by a 0 byte. The problem
- # is to squash them together into output lines containing 72 characters
- # each. A semicolon must be added between input lines. Runs of blanks
- # and tabs in input lines must be squashed into single blanks.
- # Occurrences of "**" in input lines must be replaced by "^".
- #
- # Here's a test case:
- test = """\
- d = sqrt(b**2 - 4*a*c)
- twoa = 2*a
- L = -b/twoa
- R = d/twoa
- A1 = L + R
- A2 = L - R\0
- """
- # The program should print:
- # d = sqrt(b^2 - 4*a*c);twoa = 2*a; L = -b/twoa; R = d/twoa; A1 = L + R;
- #A2 = L - R
- #done
- # getline: delivers the next input line to its invoker
- # disassembler: grabs input lines from getline, and delivers them one
- # character at a time to squasher, also inserting a semicolon into
- # the stream between lines
- # squasher: grabs characters from disassembler and passes them on to
- # assembler, first replacing "**" with "^" and squashing runs of
- # whitespace
- # assembler: grabs characters from squasher and packs them into lines
- # with 72 character each, delivering each such line to putline;
- # when it sees a null byte, passes the last line to putline and
- # then kills all the coroutines
- # putline: grabs lines from assembler, and just prints them
- from Coroutine import *
- def getline(text):
- for line in string.splitfields(text, '\n'):
- co.tran(codisassembler, line)
- def disassembler():
- while 1:
- card = co.tran(cogetline)
- for i in range(len(card)):
- co.tran(cosquasher, card[i])
- co.tran(cosquasher, ';')
- def squasher():
- while 1:
- ch = co.tran(codisassembler)
- if ch == '*':
- ch2 = co.tran(codisassembler)
- if ch2 == '*':
- ch = '^'
- else:
- co.tran(coassembler, ch)
- ch = ch2
- if ch in ' \t':
- while 1:
- ch2 = co.tran(codisassembler)
- if ch2 not in ' \t':
- break
- co.tran(coassembler, ' ')
- ch = ch2
- co.tran(coassembler, ch)
- def assembler():
- line = ''
- while 1:
- ch = co.tran(cosquasher)
- if ch == '\0':
- break
- if len(line) == 72:
- co.tran(coputline, line)
- line = ''
- line = line + ch
- line = line + ' ' * (72 - len(line))
- co.tran(coputline, line)
- co.kill()
- def putline():
- while 1:
- line = co.tran(coassembler)
- print line
- import string
- co = Coroutine()
- cogetline = co.create(getline, test)
- coputline = co.create(putline)
- coassembler = co.create(assembler)
- codisassembler = co.create(disassembler)
- cosquasher = co.create(squasher)
- co.tran(coputline)
- print 'done'
- # end of example