dictionary/hash and '1' versus 1

Steven D'Aprano steve at REMOVE-THIS-cybersource.com.au
Sun Jan 6 01:00:53 CET 2008


On Sat, 05 Jan 2008 15:07:10 -0800, bearophileHUGS wrote:

> Paddy:
>> Not really, it seems to me to be going the exact opposite way with
>> languages with automatic type conversions being seen as not suited for
>> larger programs.
> 
> In Java you can add the number 1 to a string, and have it automatically
> converted to string before the string join... What do you think of that
> feature?

You mean special-casing the int 1 so that this works?

# Faked!
>>> x = "spam spam spam"
>>> x = x + 1
>>> x
'spam spam spam1'


but not this?

>>> x = "spam spam spam"
>>> x = x + 2
TypeError: automatic conversion between strings and ints only works for 
the int 1


How bizarre.


The problem with automatic conversions between strings and integers is 
that it isn't clear what the user wants when they do something like this:

>>> x = '1' + 1

Should x be the string '11' or the int 2? Please justify your answer.


On the other hand, if the language includes separate operators for 
addition and concatenation (say, + and &) then that sort of auto-
conversion is no longer ambiguous:

>>> '2' + 3
5
>>> '2' & 3
'23'




-- 
Steven



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