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Re: message-driven function: more explanation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg95660] Re: message-driven function: more explanation
  • From: Mariano Suárez-Alvarez <mariano.suarezalvarez at gmail.com>
  • Date: Sat, 24 Jan 2009 06:18:38 -0500 (EST)
  • References: <gl9n6q$aus$1@smc.vnet.net> <glc50f$3b3$1@smc.vnet.net>

On Jan 23, 8:09 am, dh <d... at metrohm.com> wrote:
> Hi Bert,
>
> nothing exotic here. The return value is a function that consits of a
>
> [snip]

Well, there is one thing which may be mildly exotic
for those not familiar with it: the function is
returned is wrapped by a closure, which is why it
is able to retain the value of the counter variable.

(The closure is not air-tight, though:

  In[1]:= f[a_] := Module[{aa = a, ff},
     ff[i_] := (aa += i; aa);
     ff
     ];

  In[2]:= q  = f[0]

  Out[2]= ff$14

  In[3]:= q[2]

  Out[3]= 2

  In[4]:= aa$14 = 0;

  In[5]:= q[3]

  Out[5]= 3

Can one get a really closed closure?)

-- m


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