Lisping has finally made it into the App Store. For those who don't know, Lisping is a Scheme development environment designed around the concept of editing the parse tree, an approach chosen because of its suitability to the iPad's touchscreen interface.
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.
With a syntax identical to its parse tree, Scheme is an ideal language to be edited in this way. Additionally its flexibility and terse syntax make it the perfect language for coding on the go. Lisping's built-in parser and parse-tree based layout engine take care of some of many of Scheme's more tedious aspects such as closing parentheses. With Lisping you simply cannot write code with an unbalanced number of parentheses. The REPL too just became easier, if you want to see what a chunk of code does, it is as simple as touching it and pressing execute. A popover will appear with the results. See for youself in this demo.
Lisping is a fully capable Scheme Development environment for the iPad, but as such a radical departure from the traditional code editing model it is also an experiment. If you have any comments, suggestions, or complaints please get in touch with me at firstname.lastname@example.org.
Posted on 05 Apr 2012
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