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To: python-list@python.org
From: Dennis Lee Bieber <wlfraed@ix.netcom.com>
Subject: Re: code review
Date: Mon, 02 Jul 2012 01:20:14 -0400
Organization: > Bestiaria Support Staff <
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Xref: csiph.com comp.lang.python:24764

On 02 Jul 2012 01:28:25 GMT, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> declaimed the following in
gmane.comp.python.general:

> 
> When you make unsafe assumptions about an operator, and get bitten by it, 
> the *correct* conclusion should be that the assumption was wrong, not 
> that the language is wrong.
>
	Well, to be fair, the assumption is not about "an operator" but
about a sequence of operators. I don't think there was any question that
"<" was not a "less than comparison" operator.

	OTOH:  consider

>>> 5 ^ 2
7
>>> 1 < 3 < 5
True
>>> 3 < 5 < 1
False
>>> True < 1
False
>>> 
vs

> 5 ^ 2
[1] 25
> 1 < 3 < 5
Error: unexpected '<' in "1 < 3 <"
> TRUE < 1
[1] FALSE
>

vs

? 5 ^ 2
 25 
? 1 < 3 < 5
True
? 3 < 5 < 1
True
? True < 1
True

vs

PS E:\UserData\Wulfraed\My Documents> 5 ^ 2
Unexpected token '^' in expression or statement.
At line:1 char:3

Unexpected token '2' in expression or statement.
At line:1 char:5

PS E:\UserData\Wulfraed\My Documents> 1 -lt 3 -lt 5
False

PS E:\UserData\Wulfraed\My Documents> 1 -lt 5 -lt 3
False

PS E:\UserData\Wulfraed\My Documents> 1 -lt 5
True

PS E:\UserData\Wulfraed\My Documents> True -lt 1
The term 'True' is not recognized as the name of a cmdlet, function,
script file, or operable program. Check the spelling of the name, or if
a path was included, verify that the path is correct and try again.
At line:1 char:5
+ True <<<<  -lt 1
    + CategoryInfo          : ObjectNotFound: (True:String) [],
CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException
 
PS E:\UserData\Wulfraed\My Documents> 'True' -lt 1
False

PS E:\UserData\Wulfraed\My Documents> 1 -lt 'True'
Bad argument to operator '-lt': Could not compare "1" to "True". Error:
"Cannot convert value "True" to type "System.Int32". Error: "Input
string was not in a correct format."".
At line:1 char:6
+ 1 -lt <<<<  'True'
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : BadOperatorArgument
 
PS E:\UserData\Wulfraed\My Documents> $True -lt 1
False

PS E:\UserData\Wulfraed\My Documents> $True -eq 1
True



	Python, R, Visual Basic 6, PowerShell 2, respectively.

	Obviously, someone coming over from VB or R who hasn't read the
Python reference is going to wonder why they are getting incorrect
results when doing exponentiation (Isn't there an interface from Python
to R? Now there is confusion in the making!)

{Hmmm... R accepts BOTH 5 ** 2 and 5 ^ 2 for exponentiation}

-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
        wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/