What systems have you been using where reading involves a more than superficial understanding of the program? Normally, a reader doesn't even know how many argu

What systems have you been using where reading involves a more than superficial understanding of the program? Normally, a reader doesn't even know how many arguments ought to be given to each function or syntactic form, nor does it know the difference between macro invocation and a function call. There is no need for the reader to know what the syntactic forms in the base or extended language are. The value of s-expressions (or any notation that explicitly encodes the tree shape) is that the reader can function without that knowledge.