PDP-8 had auto-increment locations down in low memory in similar style.

I suppose the device addressing through memory on lots of machines counts as 
magic too,

L.

Sent from my iPad

On 22 May 2011, at 06:39, "Thomas Green" <green...@ntlworld.com> wrote:

> 
> Kevlin Henney wrote:
>> To really demonstrate autoboxing you need to allow the compiler to  
>> convert from int to Integer:
>>   Integer x = 1000;
>>   Integer y = 1000;
>> However, if you are after interesting counterintuitive corner cases,  
>> change the constant to 100:
>>   Integer x = 100;
>>   Integer y = 100;
>> A direct equality comparison will now compare true because, by  
>> default, the JVM caches the Integer objects for values from -128 to  
>> +127 (the range can be extended as an optimisation).
>> In other words, your corner case has a corner case. Magic.
> 
> 
> Back in the sixties, the autocode for the Atlas machine at Harwell had  
> a fine piece of magic. As an outsider, I could book for an occasional  
> week there, and while I was there I could run programs twice a day  
> iirc. I once spent two of those 7 days trying to find out why my  
> program wouldn't work, panicking desperately about meeting my target,  
> before discovering that of its 128 registers (called B-lines), the one  
> I had chosen to use was fitted with a hardware conversion to return  
> log-2 of any quantity stored in it.
> 
> All the higher-numbered B-lines silently did special things,  
> apparently. Great if you knew about them. Tough otherwise.
> 
> (For those of you who came late to the party and missed the early  
> days, an 'autocode' was a slightly-Englished version of machine code.  
> Bit like a penny-farthing - if you stayed on, people admired you, but  
> when you fell off it really showed.)
> 
> Thomas
> 
> 
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