A simple atoi function in ruby.

atoi.rb

# A simple translate from a string to integer.
# A minus before all numbers will be consider to be a negative number.


def atoi(str)
	return str if !str.is_a? String

	fixed_str = fix(str)

	result = 0
	fixed_str.each_char do |c|
		result = result*10 + c.to_i
	end
	fixed_str[0]=='-' ? -result : result
end


def fix(str)
	minus = false

        str = str.split('.').first

	#Consider a minus symbol before all numbers as a negative number.
	str.each_char do |c|
		minus = true if c == '-'
		break if( c>='0' && c<='9')
	end

	str.each_char do |c|
		str.delete!(c) if(c<'0' || c>'9') 
	end

	minus ? "-#{str}" : str
end


atoi('123').should == 123
atoi('-af+240.sf').should == -240
atoi(';sf2.34-34').should == 2