[plt-scheme] reference to undefined identifier

> hi, i am new and i have a problem.i couldn't find any solution :( i am
> sure it is a basic and an easy problem..
> i saw these codes in a scheme book but they didn't work.it gives this
> problem: reference to undefined identifier: accumulate. i don't know
> what that means.what can i do to fix? i use pretty big language.

I'm assuming you're looking at the Simply Scheme textbook.  Is that right?

If so, you need to do one more thing: the Simply Scheme texbook
assumes that you're loaded some special definitions that aren't
built-in.  Those definitions are available from Brian Harvey's
website, but you may more easily grab those definitions from the
Simply Scheme package on PLaneT.  See:

    http://hkn.eecs.berkeley.edu/~dyoo/cs3/simply-scheme/

for installation instructions.