def Functions::substring( string, start, length=nil )
ruby_string = string(string)
ruby_length = if length.nil?
ruby_string.length.to_f
else
number(length)
end
ruby_start = number(start)
return '' if (
ruby_length.nan? or
ruby_start.nan? or
ruby_start.infinite?
)
infinite_length = ruby_length.infinite? == 1
ruby_length = ruby_string.length if infinite_length
ruby_start = ruby_start.round - 1
ruby_length = ruby_length.round
if ruby_start < 0
ruby_length += ruby_start unless infinite_length
ruby_start = 0
end
return '' if ruby_length <= 0
ruby_string[ruby_start,ruby_length]
end