Anyone who has tried to edit code on the iPad through a traditional textview knows that it doesn’t work well. Editing source code character by character is a concept wedded to the keyboard and it is inappropriate for the iPad, a device with no keyboard. Lisping abandons this model and allows you to edit your code via the parse tree. Rather than manipulating ranges of characters Lisping focusses on selecting, creating and moving syntax elements, a task ideally suited to the iPad’s touchscreen interface, and also - more than a little bit fun.
http://slidetocode.com/2012/04/05/lisping-released/