From: Robert Klemme <shortcutter@...>
Date: 2007-05-02T20:40:09+09:00
Subject: Re: Inverse scanf: finding format specifers of existing fields

On 02.05.2007 12:47, Bil Kleb wrote:
> I have files full of numbers that I need to twiddle,
> but the format of the numbers cannot change[1], e.g.,
> 
>  '0.4577' -> '0.7728'
> 
> or
> 
> '-2.345e-02' -> ' 1.232e-03'
> 
> Using scanf for the output seems to be the solution to
> the second half of the problem, but how does one derive
> the format specifier string of the input fields, which vary?

If there is a fixed number of formats you can probably use a cascade of 
RX matches.  Otherwise it probably becomes a bit more complex like 
matching sequences of digits and measuring their lengths.

 >> md = %r{^(\d+)\.(\d+)?$}.match('0.4577')
=> #<MatchData:0x7ef61250>
 >> pa="%#{md[0].size}.#{md[2].size}f"
=> "%6.4f"
 >> pa % 0.4577111
=> "0.4577"

HTH

	robert