I hit return in the REPL and nothings happening. Whats going on?
One possibility is that the expression you just asked Lisp to evaluate contains an infinite loop or is simply taking a very long time to evaluate. (Some standard new Lisper exercises are designed to lure you into this trap; if you’ve written, say, a naive implementation of a function to compute the nth Fibonacci number, evaluating even something as seemingly innocuous as (fib 30) can take quite a bit longer than you might be willing to wait.) The other possibility is that you simply haven’t typed a complete Lisp expression—most Lisp environments allow you to include line breaks in expressions you type at the REPL since they can use the parentheses to determine when you’ve typed a complete expression. If you haven’t yet closed all your parens, there’s nothing for Lisp to evaluate. (Some Lisp environments will help you out with this. SLIME for instance, flashes the opening paren corresponding to each closing paren you type and if you hit return in the middle of an expression puts a messa
+ +One possibility is that the expression you just asked Lisp to evaluate +contains an infinite loop or is simply taking a very long time to +evaluate. (Some standard new Lisper exercises are designed to lure you +into this trap; if you’ve written, say, a naive implementation of a +function to compute the nth Fibonacci number, evaluating even +something as seemingly innocuous as \code{(fib 30)} can take quite a +bit longer than you might be willing to wait.) + +The other possibility is that you simply haven’t typed a complete Lisp +expression–most Lisp environments allow you to include line breaks in +expressions you type at the REPL since they can use the parentheses to +determine when you’ve typed a complete expression. If you haven’t yet +closed all your parens, there’s nothing for Lisp to evaluate. (Some +Lisp environments will help you out with this. SLIME for instance, +flashes the opening paren corresponding to each closing paren you type +and if you hit return in the middle of
