I need to convert all the even indexed characters in a string to become uppercase, while the odd indexed characters stay lowercase. I've tried this, but it keeps failing and I'm not sure why. I'd appreciate some help!
for i in 0..string.length if (i % 2) == 0 string[i].upcase else string[i].downcase end end 
"foobar".gsub(/(.)(.?)/){$1.upcase + $2.downcase} # => "FoObAr" "fooba".gsub(/(.)(.?)/){$1.upcase + $2.downcase} # => "FoObA" There you go:
string = "asfewfgv" (0...string.size).each do |i| string[i] = i.even? ? string[i].upcase : string[i].downcase end string # => "AsFeWfGv" We people don't use for loop usually, that's why I gave the above code. But here is correct version of yours :
string = "asfewfgv" for i in 0...string.length # here ... instead of .. string[i] = if (i % 2) == 0 string[i].upcase else string[i].downcase end end string # => "AsFeWfGv" You were doing it correctly, you just forgot to reassign it the string index after upcasing or downcasing.
You have two problems with your code:
for i in 0..string.length should be for i in 0...string.length to make the last character evaluated string[string.length-1], rather than going past the end of the string (string[string.length]); andstring[i] must be an L-value; that is, you must have, for example, string[i] = string[i].upcase.You can correct your code and make it more idiomatic as follows:
string = "The cat in the hat" string.length.times do |i| string[i] = i.even? ? string[i].upcase : string[i].downcase end string #=> "ThE CaT In tHe hAt" 