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From: Dick Hendrickson <dick.hendrick...@att.net>
Newsgroups: comp.lang.fortran,comp.lang.pl1
Subject: Re: Array constructors and types
Date: Sat, 03 Mar 2012 06:59:58 -0600
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On 3/2/12 1:19 AM, Robin Vowels wrote:
> On Feb 29, 1:03 pm, Dick Hendrickson<dick.hendrick...@att.net>  wrote:
>> On 2/28/12 8:08 AM, Robin Vowels wrote:
>>
>>> In the case of Fortran, it's simply resolved by choosing the longest
>>> length of the elements in the constructor list.
>>
>>> In PL/I, the problem doesn't arise, because elements in a
>>> character array are not required to have the same length.
>>> (See the attribute VARYING in the PL/I example that I gave earlier.)
>>
>>>>> The constructor list is clearly an array of characters.
>>>>> It's not even a mixture of types, which is what others were worring
>>>>> about.
>>
>>>> One clearly mixes different types: They all differ in the length-type
>>>> parameter.
>>
>>> As I said before, choose the longest length.  Then nothing is lost.
>>
>> There are two problems with this.
>>
>> One is practical, given
>>         [ ( repeat( 'x', int_func(i) ) , i = 1,N) ]
>> how do you find, in a reasonably efficient manner, the longest length?
>> There seem to be only two solutions.  One is to evaluate int_func(i) N
>> different times, save the results, and (trivially) compute the maximum.
>>    Then use the saved list of int_func(i) to do the repeat function and
>> append enough blanks.  Clearly, the Fortran side-effects rules don't
>> allow you to evaluate int_func(i) from 1 to N twice.  The other is to
>> just march through the list and go back and add blanks each time a
>> larger length is encountered.  Since N can be large, neither was
>> believed to be practical.
>
> Think of it as an assignmenet to a character array.
> It's no more difficult.
No, you're missing my point.  In a character array assignment the 
element size is known and each individual value can be converted to the 
right length one at a time.  There are no surprises; no need to go back 
and fix something or to look ahead to see what the "real" length is.

Dick Hendrickson