Sep 28, 2000, 6:56 AM
Post #2 of 2
Auto-increment and Auto-decrement
"++" and "--" work as in C. That is, if placed before a
variable, they increment or decrement the variable before
returning the value, and if placed after, increment or
decrement the variable after returning the value.
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]*$/, the increment is done as a string, preserving each
character within its range, with carry:
print ++($foo = '99'); # prints '100'
print ++($foo = 'a0'); # prints 'a1'
print ++($foo = 'Az'); # prints 'Ba'
print ++($foo = 'zz'); # prints 'aaa'
The auto-decrement operator is not magical.
Auto-decrement on strings is undefined -- that is, the string is first converted to a number somehow -- because it is not a consistent process. What is --"a"?
Jeff "japhy" Pinyan -- accomplished author, consultant, hacker, and teacher