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Forum => newLISP in the real world => Topic started by: joejoe on June 10, 2012, 08:06:13 PM

Title: int does not like 08 and 09?
Post by: joejoe on June 10, 2012, 08:06:13 PM
Code Select
> (int 00)
0

> (int 01)
1

> (int 02)
2

> (int 03)
3

> (int 04)
4

> (int 05)
5

> (int 06)
6

> (int 07)
7

> (int 08)
0

> (int 09)
0

> (int 10)
10

> (int 11)
11



ok. nL is playing tricks on me! ;0)



Manual says:


QuoteIf exp evaluates to a string, the string must start with a digit; one or more spaces; or the + or - sign.


Code Select
(set 'my-nums '("00" "08" "40"))

(int (nth 1 my-nums))

;-> 0

I managed to get float to come to my rescue:


Code Select

(int (float (nth 1 my-nums)))

;-> 8

What's up w/ int and the 08 and 09 numbers?



Thank you.
Title: Re: int does not like 08 and 09?
Post by: saulgoode on June 10, 2012, 09:36:41 PM
Numeric constants that start with a zero are treated as octal numbers (//http), therefore '8' and '9' are not valid digits.
Title: Re: int does not like 08 and 09?
Post by: Patrick on June 10, 2012, 09:38:46 PM
See here in the documentation (//http)


QuoteThe string must begin with '0x' for hexadecimal strings or '0' (zero) for octal strings. If exp is invalid, int returns nil as a default value if not otherwise specified.


If you prefix it with a 0, it will be evaluated as octal. There is no 9 or 8 in octal, since 8 dec is 10 oct.
Title: Re: int does not like 08 and 09?
Post by: joejoe on June 10, 2012, 10:19:59 PM
Gotcha both on that, saulgoode and Patrick,



Never heard of octals but now I know better. :0)



Thanks again for pointing it out exactly!
Title: Re: int does not like 08 and 09?
Post by: cormullion on June 11, 2012, 12:39:50 AM
I learnt that the hard way - an old post //http://newlisper.wordpress.com/2006/09/18/my-mistake-2/ describes my experience in tedious detail...
Title: Re: int does not like 08 and 09?
Post by: Patrick on June 11, 2012, 07:16:55 AM
Quote from: "cormullion"I learnt that the hard way - an old post //http://newlisper.wordpress.com/2006/09/18/my-mistake-2/ describes my experience in tedious detail...


To be fair I found it a bit weird when I first read about it as well. I think having h and o prefixes would have been clearer, but I guess as long as one knows about it it's not too hard to avoid it as you have shown in your post.
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