On Apr 13, 2011, at 5:31 AM, Pat Maddox wrote:

On Apr 12, 2011, at 3:24 PM, Simon Denier wrote:

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On 12 avr. 2011, at 23:47, Werner Kassens wrote:

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hi, i have a testsuite that is a subclass of TestCase with this method:

testStupid |a| a :=#(1). self assert: a first isNumber . a :=a at:1 put: nil.

if i run the test once, it succeeds, but but when i run it a second time it fails. this seems to be sligthly counterintuitive, or how do i have to understand it?

Interesting, I would never have guessed the test would be broken at first sight. So maybe some people enlightened in the ways of the compiler can provide a better explanation than me. Here is my guess:

#(1) is a special construct which creates a compile-time array. The compile-time makes the trick: in short the array is more or less encoded directly into the bytecodes of the method as a constant. But modifying the array with #at:put: directly modifies the bytecodes in the compiled method itself. So you create a side-effect directly into your method.

Am I the only one to find this a bit dangerous and not intuitive? Is it a well-known behavior?

I would never have guessed that in a million years.

I like this method: mystery 'mystery' isString ifTrue: ['mystery' become: {0}]. 'mystery' at: 1 put: 'mystery' first + 1. ^ 'mystery' first. -- Marcus Denker -- http://www.marcusdenker.de INRIA Lille -- Nord Europe. Team RMoD.