Cannot assign to property: 'self' is immutableというエラーメッセージはSwiftで見られるもので、これはオブジェクトのプロパティや自身の値を変更しようとした際に、そのオブジェクトが不変（immutable）であることを示しています。具体的には、以下のような状況でこのエラーが発生することが一般的です：
def permutation(list, start, end):
if (start == end):
print list
else:
for i in range(start, end + 1):
list[start], list[i] = list[i], list[start] # The swapping
permutation(list, start + 1, end)
list[start], list[i] = list[i], list[start] # Backtracking
permutation([1, 2, 3], 0, 2) # The first index of a list is zero
import copy
_stack=[]
def permutation(list, start, end,count):
if (start == end):
print(list)
else:
for i in range(start, end + 1):
_backup=copy.copy(list);
list[start], list[i] = list[i], list[start] # The swapping
_stack.append(_backup[i])
print("swapped",_backup[start],"->",_backup[i],"then",list,_stack)
permutation(list, start + 1, end,count)
_backup=copy.copy(list);
list[start], list[i] = list[i], list[start] # Backtracking
_stack.pop()
print(" backte",_backup[i],"<-",_backup[start],"then",list,_stack)
permutation(['a', 'b','c'], 0, 2,0) # The first index of a list is zero
結果はこんな感じで推移する
swapped a -> a then ['a', 'b', 'c'] ['a']
swapped b -> b then ['a', 'b', 'c'] ['a', 'b']
['a', 'b', 'c']
backte b <- b then ['a', 'b', 'c'] ['a']
swapped b -> c then ['a', 'c', 'b'] ['a', 'c']
['a', 'c', 'b']
backte b <- c then ['a', 'b', 'c'] ['a']
backte a <- a then ['a', 'b', 'c'] []
swapped a -> b then ['b', 'a', 'c'] ['b']
swapped a -> a then ['b', 'a', 'c'] ['b', 'a']
['b', 'a', 'c']
backte a <- a then ['b', 'a', 'c'] ['b']
swapped a -> c then ['b', 'c', 'a'] ['b', 'c']
['b', 'c', 'a']
backte a <- c then ['b', 'a', 'c'] ['b']
backte a <- b then ['a', 'b', 'c'] []
swapped a -> c then ['c', 'b', 'a'] ['c']
swapped b -> b then ['c', 'b', 'a'] ['c', 'b']
['c', 'b', 'a']
backte b <- b then ['c', 'b', 'a'] ['c']
swapped b -> a then ['c', 'a', 'b'] ['c', 'a']
['c', 'a', 'b']
backte b <- a then ['c', 'b', 'a'] ['c']
backte a <- c then ['a', 'b', 'c'] []
このシリーズは、単なる語彙学習本というより、執筆者の机まわりに置かれる「言葉の周辺ギア」として見るとわかりやすい。書く力そのものを直接売るというより、書く人が言葉を集め、分類し、眺め、取り出しやすくする環境を提供している。楽器でいえば、演奏技術ではなく、ストラップ、ピックケース、コード表、ペダルボードに近い。Rather than viewing this series as a mere vocabulary textbook, it makes more sense to think of it as a set of “writing accessories” kept on the author’s desk. Rather than directly selling writing skills, it provides an environment that helps writers collect, categorize, and easily access words. To use a musical instrument analogy, it’s not about playing technique, but rather about the strap, pick case, chord chart, and pedalboard.https://note.com/rodz/n/na154dcf2957b
