Re: P1788 input/output

[Ned Nedialkov <nedialk@xxxxxxxxxxx>]

Dear All, 

Here are some thoughts. You may find them a bit  off, but still, wanted to share them.

(1) interval2text(x, cs)

What about 

interval2text(x, formatstring, string1, string2)

formatstring is similar to how format strings are in printf, etc. 
The key here, I think, is to settle on a small set of format strings.

string1 and string2 represent the left and right bounds rounded correctly. 
Then the user can do whatever wants with them. 

So, if x=[1.12345678e2, 2.12345678e2]

interval2text(x, "%.4e", string1, string2)

would return string1 = 1.1234e2, string2 = 2.1235e2

Then I can read back e.g. with text2interval(string1).

(2) Thinking further in terms of format strings, what about this idea. 

In C we have printf, sprintf, scanf, etc. They are all very well established. 
When reading or writing numbers, they are rounded to the nearest.

What if we have say printf_i, sprintf_i, scanf_i, etc. 
Then we can have a modifier in the string format that says round down or round up.
For example, if [a,b] is an interval, I may write

printf_i("%fD  %fU", a,b);

so a is rounded down and b is rounded up.

I could also write e.g.

printf_i("%dD  %dU", a,b)

but now they are printed as integers. 

I think this may give the most flexibility, and it is not that difficult to implement. 

I think this approach is really useful, as if I write data into  a file, e.g. 
I could do in a loop

fprintf_i(f, "%dD  %dU \n", a[i], b[i])

which I can plot with say gnuplot or Matlab. If I need to produce output for an article I could do

printf_i("[%dD,  %dU] \n", a[i], b[i])


If the modifiers down "D" and up "U" are missing, printf_i just calls the standard printf.
That is, we can have wrappers for the standard C input/output functions.

Of course, similar considerations should apply to any other language.  

It could be tricky in C++. If A=[a,b]
then we may need to say what the output of 

cout << A << endl;

is. 

I would output 

[a, b] 

where a and b are rounded correctly strings in the default precision. 

Ned