From: Alex DeCaria <alex.decaria@...>
Date: 2010-04-13T20:20:21+09:00
Subject: Re: Method to groom a string to floating point representation

Josh Cheek wrote:
> It would probably be easier if you provided a set of tests we could 
> check
> our function against, where we could be confident our function was 
> correct
> once it passed all the tests.

Here are some examples of what it should do:

Delete any characters other than digits, +, -, e, E, or .:
'-24.5fge4x'5 => '-24.5e45'

Delete any extra decimals:
'2.4.5' => '2.45'
'2..45' => '2.45'

Delete any decimals in an exponent:
'245e7.6' => '2.45e76'

Delete any extra or misplaced + or – signs:
'+45-68+e+45-' => '4568e+45'

Delete any extra or misplaced ‘e’ or ‘E’ characters (first occurance of 
'e' or 'E' has precedence unless it doesn't make sense):
'4.67e6e-7' => '4.67e67'
'+e4.67e-7' => '+4.67e-7'

The motivation for this is for a GUI input textbox, so that if the user 
enters a bad string it automatically corrects it to a valid 
floating-point representation in string form before converting to a 
floating-point for calculations.  I toyed with just doing
str = str.to_f.to_s
and letting Ruby figure out the floating point respesentation, but I'd 
like more control over how the string is converted to floating point 
representation.  For example, I want
'2..45e9' => '2.45e9', whereas '2..45e9'.to_f.to_s => '2.0'

--Alex


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