interpreter

I have heard of deferred evaluation in python (for example here ), is it just referring to how lambdas are evaluated by the interpreter only when they are used? Or is this the proper term for describing how, due to python's dynamic design, it will not catch many errors until runtime? Or am I missing something entirely? Dietrich's answer is a good one, but I just want to add that the simplest form of deferred evaluation is the if statement: if True: x = 5 else: x = y # huh? what is y? This code parses and runs correctly, although the else clause makes no sense - y is undefined. The else clause

Everytime I use these keys in the interpreter I keep getting symbols like this appearing: [[D^[[C I'm using Linux Mint 12 in ZSH, however I'm getting the same result in Ubuntu with bash. Also, same thing in ssh. The stock OCaml toplevel doesn't have line editing built in. I use rlwrap : $ cat bin/ocaml #!/bin/sh exec rlwrap /usr/local/bin/ocaml "$@" Using the toplevel without something like this is quite painful, in my opinion! Other possibilities are to run the toplevel under emacs (a popular choice, I think), or to use utop . I haven't used utop, but it sounds cool. Another option is to use:

I'm wondering about the purpose, or perhaps more correctly, the tasks of the "reader" during interpretation/compilation of Lisp programs. From the pre-question-research I've just done, it seems to me that a reader (particular to Clojure in this case) can be thought of as a "syntactic preprocessor". It's main duties are the expansion of reader macros and primitive forms. So, two examples: 'cheese --> (quote cheese) {"a" 1 "b" 2} --> (array-map "a" 1 "b" 2) So the reader takes in the text of a program (consisting of S-Expressions) and then builds and returns an in-memory data-structure that can