Add alphabetseq

alphabetseq

@@ -0,0 +1,54 @@
+#!/usr/bin/env python3
+import itertools
+import sys
+
+
+def decimal_to_alphabet(n: int, alphabet: str) -> str:
+	if n == 0:
+		return alphabet[0]
+	base = len(alphabet)
+	digits = []
+	while n:
+		digits.append(alphabet[n % base])
+		n //= base
+	return ''.join(digits[::-1])
+
+
+def alphabet_to_decimal(s: str, alphabet: str) -> int:
+	base = len(alphabet)
+	l = len(s)
+	return sum(alphabet.index(s[l - 1 - i]) * base ** i for i in range(l))
+
+
+def test():
+	assert alphabet_to_decimal('ff', '0123456789abcdef') == 255
+	assert alphabet_to_decimal('100', '0123456789abcdef') == 256
+	assert decimal_to_alphabet(255, '0123456789abcdef') == 'ff'
+	assert decimal_to_alphabet(256, '0123456789abcdef') == '100'
+	assert decimal_to_alphabet(0, '0123456789') == '0'
+
+
+if __name__ == '__main__':
+	if len(sys.argv) == 2 and sys.argv[1] == '--test':
+		test()
+	elif len(sys.argv) == 4 or (len(sys.argv) == 5 and sys.argv[2] == '--decimal'):
+		if len(sys.argv) == 4:
+			alphabet = sys.argv[1]
+			start, stop = map(lambda x: alphabet_to_decimal(x, alphabet), sys.argv[2:])
+		else:
+			alphabet = sys.argv[1]
+			start, stop = map(int, sys.argv[3:])
+		for i in range(start, stop + 1):
+			try:
+				sys.stdout.write(decimal_to_alphabet(i, alphabet) + '\n')
+			except (BrokenPipeError, IOError):
+				try:
+					sys.stdout.close()
+				except IOError:
+					pass
+				break
+	else:
+		print('Usage: alphabetseq ALPHABET [--decimal] START STOP', file = sys.stderr)
+		print('Generates the sequence from START to STOP (inclusive) using ALPHABET', file = sys.stderr)
+		print('By default, START and STOP are expressed in ALPHABET. With --decimal, they are treated as decimal values instead.', file = sys.stderr)
+		print('`alphabetseq 0123456789 $N $M` is equivalent to `seq $N $M`.', file = sys.stderr)