求助 自增 自减 问题

搬砖工作者

$a=b;
$a++;
结果 是c  可是

$a=b;
$a--;
结果却是-1；
是好像任意的 字母自减结果 都-1

要怎样 把$a的值转成 a呢

zhlong8

The auto-increment operator has a little extra builtin magic to it. If you increment a variable that is numeric, or that has ever been used in a numeric context, you get a normal increment. If, however, the variable has been used in only string contexts since it was set, and has a value that is not the empty string and matches the pattern /^[a-zA-Z]*[0-9]*\z/ , the increment is done as a string, preserving each character within its range, with carry:
    print ++($foo = '99');        # prints '100'
    print ++($foo = 'a0');        # prints 'a1'
    print ++($foo = 'Az');        # prints 'Ba'
    print ++($foo = 'zz');        # prints 'aaa'
undef is always treated as numeric, and in particular is changed to 0 before incrementing (so that a post-increment of an undef value will return 0 rather than undef).
The auto-decrement operator is not magical.

所以请用 chr(ord('b') - 1)

搬砖工作者

回复 2# zhlong8


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