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From: mdw@excessus.demon.co.uk (Mark Wooding)
Subject: Re: What's the best language to learn? [was Re: Should I learn C or
 Pascal?]
Date: 1996/08/22
Message-ID: <slrn51osnb.ret.mdw@excessus.demon.co.uk>#1/1
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references: <4v26j4$hkg@news.csus.edu> <01bb8d2f$351b9500$32ee6fce@timhome2>
 <4vdon9$8nt@news1.mnsinc.com>
organization: Straylight Development Lab
reply-to: mdw@excessus.demon.co.uk
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 comp.edu,comp.lang.ada,comp.lang.c,comp.lang.c++,comp.unix.programmer
Date: 1996-08-22T00:00:00+00:00
List-Id: <comp.lang.ada>


Szu-Wen Huang <huang@mnsinc.com> wrote:

> Lofty, ungraspable concepts like:
> 
>   void swap(int *a, int *b)
>   {
>     int c = *a;
> 
>     *b = *a;
>     *a = c;
>   }
>   ...
>   swap(&a, &b);
>   ...
> 
> ?  swap(), by the way, is a primitive for just about every algorithms
> text I've ever read.  Does knowing the computer must:
> 
>   LOAD r1, a
>   ADD  something_else_totally_unrelated
>   LOAD r2, b
>   INC  some_counter_from_another_place
>   STOR r1, b
>   INC  that_same_counter_but_we_just_need_to_fill_the_slot
>   STOR r2, a
> 
> in order to swap two integers aid in the understanding of swap()?
> I agree that we need to break an algorithm down to primitives, but
> are you actually saying swap(), for instance, isn't primitive enough?

I think you're deliberately trying to choose a nasty architecture.
We're talking about teaching, I think, so why not choose an easy one?

; --- swap ---
;
; Just like void swap(int *a,int *b)

swap		LDR	a3,[a1]
		LDR	a4,[a2]
		STR	a3,[a2]
		STR	a4,[a1]
		MOV	pc,lr

Simple.  (And now there's a 200MHz version of this processor, so it's
not /that/ old-fashioned.)
-- 
[mdw]

`When our backs are against the wall, we shall turn and fight.'
		-- John Major