[plt-scheme] Re: Why "lambda"?

From: Prabhakar Ragde (plragde at uwaterloo.ca)
Date: Fri May 29 11:35:33 EDT 2009

wooks wrote:

> I tend to go for a 3rd option. Put the textbook back on the shelf and
> find one written in English.
> Hence alot of what I learned about Theory of Computation comes from
> Daniel Cohens - Introduction to Computer Theory instead of the
> prescribed Sipser.

I ordered this through interlibrary loan to have a look at it, as I have 
taught courses on this subject (though not recently, as I am having too 
much fun teaching about functional programming).

It seems like a decent book, but it does have deltas, lambdas, and 
sigmas. It even uses the Cyrillic character "zhe" at one point (the one 
that looks like a sheaf of wheat). It also uses set notation regularly. 
Cohen does write out set comprehensions a bit, as in

{a^n b^n for n = 1 2 3 4 ...}

instead of

{a^n b^n | n \in N}.

I have problems with the Sipser textbook (which I have used in a 
course), but they aren't related to the density of the mathematics. 
There are some books in this area (e.g. the original Hopcroft and 
Ullman) which are dense enough to be problematic for many students.

But this is not solely a matter of notation. The classic Kernighan & 
Ritchie book on C is dense without using any symbols that don't appear 
on a computer keyboard. I couldn't use it for the mean student. But I 
could (and do) use HtDP.

I suggest to you, wooks, that it is not the use of Greek symbols, but 
the quality of the exposition that matters to you. You are willing to 
forgive Cohen his Greek (and a bit of Russian) because he uses it 

HtDP sensibly rewrote `car' and `cdr' to `first' and `rest', but did not 
rewrite `lambda'. I make this a teaching point. `lambda' has 
considerable historical resonance, and a common meaning to many people, 
just as a capital sigma or Leibnitz's long S does. --PR

Posted on the users mailing list.