Anonymous user
Execute a Markov algorithm: Difference between revisions
→{{header|Python}}: Comment on flexibility and addition of latest ruleset.
(→Rulesets: More than three, currently.) |
(→{{header|Python}}: Comment on flexibility and addition of latest ruleset.) |
||
Line 533:
The example uses a regexp to parse the syntax of the grammar. This regexp is multi-line and verbose, and uses named groups to aid in understanding the regexp and to allow more meaningful group names to be used when extracting the replacement data from the grammars in function <code>extractreplacements</code>.
The example gains flexibility by not being tied to specific files. The functions may be imported into other programs which then can provide textual input from their sources without the need to pass 'file handles' around.
<lang python>import re
def extractreplacements(grammar):▼
return [ (matchobj.group('pat'), matchobj.group('repl'), bool(matchobj.group('term')))▼
for matchobj in re.finditer(syntaxre, grammar)▼
if matchobj.group('rule')]▼
def replace(text, replacements):▼
while True:▼
for pat, repl, term in replacements:▼
if pat in text:▼
text = text.replace(pat, repl, 1)▼
if term:▼
return text▼
break▼
else:▼
return text▼
syntaxre = r"""(?mx)
Line 542 ⟶ 559:
)$
"""
grammar1 = """\
# This rules file is extracted from Wikipedia:
Line 553 ⟶ 570:
a never used -> .terminating rule
"""
grammar2 = '''\
# Slightly modified from the rules on Wikipedia
Line 563 ⟶ 580:
a never used -> .terminating rule
'''
grammar3 = '''\
# BNF Syntax testing rules
Line 607 ⟶ 624:
1+_ -> 1
_+_ ->
'''
grammar5 = '''\
# Turing machine: three-state busy beaver
#
# state A, symbol 0 => write 1, move right, new state B
A0 -> 1B
# state A, symbol 1 => write 1, move left, new state C
0A1 -> C01
1A1 -> C11
# state B, symbol 0 => write 1, move left, new state A
0B0 -> A01
1B0 -> A11
# state B, symbol 1 => write 1, move right, new state B
B1 -> 1B
# state C, symbol 0 => write 1, move left, new state B
0C0 -> B01
1C0 -> B11
# state C, symbol 1 => write 1, move left, halt
0C1 -> H01
1C1 -> H11
'''
text1 = "I bought a B of As from T S."
text2 = "I bought a B of As W my Bgage from T S."
text3 = '_1111*11111_'
text4 = '000000A000000'
▲def extractreplacements(grammar):
▲ return [ (matchobj.group('pat'), matchobj.group('repl'), bool(matchobj.group('term')))
▲ for matchobj in re.finditer(syntaxre, grammar)
▲ if matchobj.group('rule')]
▲def replace(text, replacements):
▲ while True:
▲ for pat, repl, term in replacements:
▲ if pat in text:
▲ text = text.replace(pat, repl, 1)
▲ if term:
▲ return text
▲ break
▲ else:
▲ return text
if __name__ == '__main__':
assert replace(text1, extractreplacements(grammar1)) \
Line 636 ⟶ 661:
assert replace(text1, extractreplacements(grammar2)) \
== 'I bought a bag of apples from T shop.'
# Stretch goals
assert replace(text2, extractreplacements(grammar3)) \
== 'I bought a bag of apples with my money from T shop.'
assert replace(text3, extractreplacements(grammar4)) \
== '11111111111111111111'
assert replace(text4, extractreplacements(grammar5)) \
== '00011H1111000'</lang>
=={{header|Ruby}}==
| |||