Boo

Substraction operator for arrays (+ bug on addition operator?)

Details

  • Type: New Feature New Feature
  • Status: Open Open
  • Priority: Minor Minor
  • Resolution: Unresolved
  • Affects Version/s: 0.9
  • Fix Version/s: 0.9.5
  • Component/s: Compiler, Runtime (Boo.Lang)
  • Labels:
    None
  • Number of attachments :
    0

Description

Adding the substraction operator on boo arrays would be a nice handy feature :

>>>cities = ['Tokyo', 'Barcelona', 'Moscow', 'Kuala Lumpur', 'Sidney']
>>>visited = cities - ['Moscow', 'Sidney']

Would give:

['Tokyo', 'Barcelona', 'Kuala Lumpur']

Also there is surely a bug with array's '+ operator' :

>>> cities = ['Tokyo', 'Barcelona', 'Moscow', 'Kuala Lumpur']
>>>cities += 'London'

Gives:
['Tokyo', 'Barcelona', 'Moscow', 'Kuala Lumpur', L, o, n, d, o, n]

Hardly the expected and preferable behavior I think?

Activity

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Rodrigo B. de Oliveira added a comment -

Oddly enough that's the right behavior. You can Add anything IEnumerable to a List in which case all the elements are added. string enumerates over its characters.

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Rodrigo B. de Oliveira added a comment - Oddly enough that's the right behavior. You can Add anything IEnumerable to a List in which case all the elements are added. string enumerates over its characters.
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Arron Washington added a comment -

It violates the principle of least surprise, even though its technically correct, I think is what Cedric is getting at, Rodrigo.

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Arron Washington added a comment - It violates the principle of least surprise, even though its technically correct, I think is what Cedric is getting at, Rodrigo.
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Avishay Lavie added a comment -

I agree - this behavior is highly unintuitive. Technically it's rather hard to circumvent (perhaps just hard-coding a special case for strings?) but that doesn't make it less of a (bad) surprise.
A different option would be to separate the add-single-item and the concatenate-with-other-list behavior. Consider, for example, reserving "+" for "add this item" and "&" for "concatenate with items in this enumerable". 

cities = ['Tokyo', 'Barcelona', 'Moscow', 'Kuala Lumpur', 'Sidney']
cities += 'London'
>>> ['Tokyo', 'Barcelona', 'Moscow', 'Kuala Lumpur', 'Sidney', 'London']
cities &= 'London'
>>> ['Tokyo', 'Barcelona', 'Moscow', 'Kuala Lumpur', 'Sidney', 'London', L, o, n, d, o ,n]
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Avishay Lavie added a comment - I agree - this behavior is highly unintuitive. Technically it's rather hard to circumvent (perhaps just hard-coding a special case for strings?) but that doesn't make it less of a (bad) surprise. A different option would be to separate the add-single-item and the concatenate-with-other-list behavior. Consider, for example, reserving "+" for "add this item" and "&" for "concatenate with items in this enumerable". cities = ['Tokyo', 'Barcelona', 'Moscow', 'Kuala Lumpur', 'Sidney'] cities += 'London' >>> ['Tokyo', 'Barcelona', 'Moscow', 'Kuala Lumpur', 'Sidney', 'London'] cities &= 'London' >>> ['Tokyo', 'Barcelona', 'Moscow', 'Kuala Lumpur', 'Sidney', 'London', L, o, n, d, o ,n]

People

  • Assignee:
    Unassigned
    Reporter:
    Cedric Vivier
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    Updated: