FatGeekUK

Every language has its rough spots.

Ruby for instance does not handle array slices very nicely.

>> a = [1, 2, 3]
=> [1, 2, 3]
>> a[0]
=> 1
>> a[0..1]
=> [1, 2]
>> a[2, 3]
=> [3]
>> a[3, 4]
=> []
>> a[4, 5]
=> nil


 

Now, thats evil. Why should a[3, 4] give you an empty array (which is expected) but a[4, 5] give you nil!

But, Ruby gets some things right.....

>> a='1,2,3'
=> "1,2,3"
>> a.split(',')
=> ["1", "2", "3"]
>> a = '1'
=> "1"
>> a.split(',')
=> ["1"]
>> a = ''
=> ""
>> a.split(',')
=> []
>>
  See that? an empty string gets you an empty array.

Theoretically, it SHOULD give you an array with a single empty text element, but it is nicer than that.

Not Evil.

Python on the other hand....

>>> a = '1,2,3'
>>> a.split(',')
['1', '2', '3']
>>> a = '1'
>>> a.split(',')
['1']
>>> a = ''
>>> a.split(',')
['']

Evil! pure and simple.

And lets look at slicing....

>>> a=(1,2,3,)
>>> a[0:1]
(1,)
>>> a[0:2]
(1, 2)
>>> a[0:3]
(1, 2, 3)
>>> a[0:4]
(1, 2, 3)
>>> a[1:4]
(2, 3)
>>> a[2:4]
(3,)
>>> a[3:4]
()
>>> a[4:5]
()
>>> a[6:7]
()
>>> a[7]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: tuple index out of range
 

In some ways that is better, slicing works nicely, but indexing a single element raises an index error.

Surely, if it is happy to slice the array outside of its limits and return a valid result, why not handle

accessing an element outside of the limits too?

 

Every year I do a bit of a clear out of my bookshelves.

I have two shelves above my desk in my office where I hold my books, the lower shelf, is my 'working set' the books I reach for all the time. The upper shelf are the 'good to haves' but are books I don't need every day. Every year, I review the books in the upper shelf, and move a selection to the boxes in the loft, so that I can push books from my 'working set' shelf up and to free space on my working set for books I need as I move speciality.

So, into the loft this year goes...

• PIC 16cXX Assembler data book
• DC01 Television Tuners
• Zilog Z8 microcontroller handbook
• Microchip Data book
• Keil 8051 Assembler/C51 manuals
• Java in a nutshell
• Programmers Guide to the Netbios
• Palm Programming
• iAPX88 Book

The assembler data books probably should have gone a couple of years ago, but
 I was a bit sentimental, I loved doing assembler coding.

From my working set to the 'upper shelf' (sort of like being demoted from the cabinet to the back benches I suppose

• Lisp (Winston & Horn)
• K&R The C Programming Language
• Managing Projects with Make

And new in the working set is a section on Django and Python.

The road to hell is paved with good intentions, Djangos MTI gives you the tools to pave yourself right into the abyss.