Take C: struct { int x; } ...; int foo () { return 0; } Should braces in both cases represent the same internal data structure

Take C: struct { int x; } ...; int foo () { return 0; } Should braces in both cases represent the same internal data structures? Probably not, the first one is for structure members and the other one for a block of statements. But in Lisp, characters are used to parse the same kind of data, which means they are same structure in all contexts. The Lisp reader has a simple approach to parsing, you don't generally change the readtable's binding based on which form you are reading (but strings, comments and code are not read the same way). Using different characters for semantics has its limit. In Clojure, take [a b] out of context. Which element is evaluated, a, b, none or both? The fact that it is a vector does not help you, because it could be a binding, an argument list or a vector constructor. Also, how something is stored inside the AST has nothing to do with its meaning at runtime. Argument lists could be passed using the stack, but you don't actually write a stack inside the source code. The fact that they are written as vectors or lists does not matter either, you still have to know the semantics. And semantics is almost never context-free.