String rewriting examples

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Here is an abstracted example of a string rewriting system using percent signs.

Here is the Python code.

import re
envPat1 = r"(.*?)%([A-Z][A-Z0-9]*)%(.*)"
envReg1 = re.compile(envPat1)

def envEval1(text1, envDict1):
	text2 = ""
	while True:
		match1 = envReg1.search(text1)
		if not match1:
			return text2 + text1
		prefix1 = match1.group(1)
		name1 = match1.group(2)
		suffix1 = match1.group(3)
		text2 += prefix1
		text3 = envDict1[name1]
		text2 += text3
		text1 = suffix1
	return text2


def srsTestDo1():
	textList1 = [
		"before %ALPHA% middle %BETA% after ",
		"start %ALPHA% continue %BETA% end"
		]
	envDict1 = {
		"ALPHA" : "(alpha pattern)",
		"BETA" : "(beta pattern)"
		}
	n1 = len(textList1)
	print("(begin list of {0:d} lines)".format(n1))
	for i1 in range(0,n1):
		print("{0:d}:".format(i1))
		text1 = textList1[i1]
		text2 = envEval1(text1,envDict1)
		print("\tbefore: \"{0:s}\"".format(text1))
		print("\tafter: \"{0:s}\"".format(text2))
	print("(end list of {0:d} lines)".format(n1))

srsTestDo1()

Here is the output of the Python code.

(begin list of 2 lines)
0:
	before: "before %ALPHA% middle %BETA% after "
	after: "before (alpha pattern) middle (beta pattern) after "
1:
	before: "start %ALPHA% continue %BETA% end"
	after: "start (alpha pattern) continue (beta pattern) end"
(end list of 2 lines)