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