From: RichardOnRails <RichardDummyMailbox58407@...>
Date: 2007-11-19T14:39:59+09:00
Subject: False positives in editing data

Hi All,

Below is a 33-line program that analyzes a set of names.
The names proper are prefixed with an optional set of period-separated
numbers.
The analysis checks for the following, and flags violations:
  1. A number may not start with zeros.
  2. No more that two numbers may be prefixed
  3. Names proper must begin with a non-digit

The program works pretty well,  except it produces "false negatives,"
which I flag on the output displayed following the program.  The
problem is around line 29 when I try to determine if a leading number
has any initial zero by using an RE and testing for Nil.

I'd welcome any ideas on how to correct my mistake(s), especially with
suggestion for improved style.

Thanks in advance,
Richard

Program
-------------------------------------------------------------------------------
MLN = 2 # MaxLeadingNumbers
input = <<DATA
05Topic 5
1Topic 1
2.002.1Topic 2.2.1
2.1Topic 2.1
2.2.02Topic 2.2.2
DATA
input.each { |sName|
	# Debug
	puts "\n" + "="*10 + "DBG", sName, "="*10+ "DBG"

	#Get leading numbers separated by periods into $1, $2, $13
	sName =~ /^([\d]+)?\.?([\d]+)?\.?([\d]+)?\.?/


	# Save match variables in n[1] ... n[MLN+1]
	n = Array.new
	(1..MLN+1).each { |i| eval  %{n[i] = $#{i}}  }

	# Debug
	print "DBG0>> ";  (1..MLN+1).each	{ |i| printf("\t#{n[i]}") };  puts
	# puts "n1=#{n[1]},  n2=#{n[2]}, n3=#{n[3]}"

	# Get and check leading, period-separated numbers in dir. names
	(1..MLN+1).each	{ |i|
		n[i] =~ /^0+/
		i_thNumberExists = n[i] ? true : false
		iThNumbrerHasLeadingZero = i_thNumberExists && (eval("$#{i}.class ==
NilClass") ?
                     true : false)
		puts "ERROR: Leading zeros in #{n[i]}" if iThNumbrerHasLeadingZero
&& (i <= MLN)
		puts "ERROR: Depth of hierarchy exceeds #{MLN}" if i_thNumberExists
&& i > MLN
	}
}


Output
---------------------------------------------

==========DBG
05Topic 5
==========DBG
DBG0>> 	05
ERROR: Leading zeros in 05

==========DBG
1Topic 1
==========DBG
DBG0>> 	1
ERROR: Leading zeros in 1	[False positive]

==========DBG
2.002.1Topic 2.2.1
==========DBG
DBG0>> 	2	002	1
ERROR: Leading zeros in 2	[False positive]
ERROR: Leading zeros in 002
ERROR: Depth of hierarchy exceeds 2

==========DBG
2.1Topic 2.1
==========DBG
DBG0>> 	2	1
ERROR: Leading zeros in 2	[False positive]
ERROR: Leading zeros in 1	[False positive]

==========DBG
2.2.02Topic 2.2.2
==========DBG
DBG0>> 	2	2	02
ERROR: Leading zeros in 2	[False positive]
ERROR: Leading zeros in 2	[False positive]
ERROR: Depth of hierarchy exceeds 2
>Exit code: 0