Re: How to know if a converted string to float is really a float number ?

Ok Tony so I will prevent with regular expression that fit to float number. It seems well optimized.

Thank you

Le vendredi 17 janvier 2020 20:28:48 UTC+1, Tony Mechelynck a écrit :

On Fri, Jan 17, 2020 at 7:29 PM Ni Va <niva...@gmail.com> wrote:
>
> HI,
>
> According to str2float help, I have tried this :
>
> '3,3e+004'->substitute(',', '.', 'g')->str2float() which return 33000 number.
>
> According to good conversion in this case it is a float num but if I replace by cases where it is not a well form of num that no have to be converted.
>
>
> '3,3e+00.4'->substitute(',', '.', 'g')->str2float() which return ????  there is a dot char in exp...
> '3,3e+0O4'->substitute(',', '.', 'g')->str2float() which return ????  there is char 'O' out of zero
>
>
> How to prevent unnecessary conversion ?
>
> Thank you

I tried the same examples, and in these last two cases I get 3.3 which
is to be expected since the conversion stops as soon as an input
character is found which would make the input invalid for a Float,
i.e., str2float('3.3e+00.4') interprets '3.3e+00' and converts it to
3.3 ; and str2float('3.3e+0O4') interprets '3.3e+0' and converts it to
3.3 — in both of these cases, trailing garbage is silently
disregarded.

In the first ("valid") case I get 33000.0 which is the number
expressed as a Float, not an (integer) Number.

If you can devise a regular expression covering what your input can
legitimately be, you could wrap the whole sequence of methods in an =~
or similar conditional (see :help expr-=~).


Best regards,
Tony.

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