Rеlаng

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Not to be confused with Relang.

Rеlаng is the simplest regular expression based language. Programs consists of two strings, each cycle, both strings replaces the first match using the other string as a regular еxpression with the other string, or remain unchanged if there are no matches. Execution terminates when both strings do not change after one cycle. This may not happen: many expressions tend to grow quadraticаlly. When displaying a program, it is recommended to display it as a single string with the two strings separated by easily recognizable separators such as [][][] or █████.

Examples

Nоte: nо gооd examples yet!
Side note: This language use . as a wildcard.

The typical execution sequence:

a{3} [][][] (aaa)?a\{3\}

The typical quadratic growth:

abc|a?b?c? [][][] a?b?c?|abc

Demonstration of . (creates a "slow growth"):

. [][][] a?.

Computational class

Insert Turing-completeness proof here

Implementation

With the help of the rе module, Python interpreters of Rеlаng can be amazingly short:

import re
str1 = input("First expression: ")
str2 = input("Second expression: ")
while True:
    temp1 = str1
    temp2 = str2
    match1 = re.search(str2, str1, re.DOTALL)
    match2 = re.search(str1, str2, re.DOTALL)
    if match1:
        span = match1.span()
        str1 = str1[:span[0]] + temp2 + str1[span[1]:]
    if match2:
        span = match2.span()
        str2 = str2[:span[0]] + temp1 + str2[span[1]:]
    print(str1 + ' █████ ' + str2)
    if (str1, str2) == (temp1, temp2):
        break