Hi list,

Here is my speculative language idea for Python:

Allow the following alternative spelling of the keyword `lambda':


(That is "Unicode Character 'GREEK SMALL LETTER LAMDA' (U+03BB).")


I have been using the Vim "conceal" functionality with a rule which visually
replaces lambda with λ when editing Python files. I find this a great improvement in
readability since λ is visually less distracting while still quite distinctive.
(The fact that λ is syntax-colored as a keyword also helps with this.)

However, at the moment the nice syntax is lost when looking at the file through another editor or viewer.
Therefore I would really like this to be an official part of the Python syntax.

I know people have been clamoring for shorter lambda-syntax in the past, I think this is
a nice minimal extension.

Example code:

  lst.sort(key=lambda x: x.lookup_first_name())
  lst.sort(key=λ x: x.lookup_first_name())

  # Church numerals
  zero = λ f: λ x: x
  one = λ f: λ x: f(x)
  two = λ f: λ x: f(f(x))

(Yes, Python is my favorite Scheme dialect. Why did you ask?)

Note that a number of other languages already allow this. (Racket, Haskell).

You can judge the aesthetics of this on your own code with the following sed command.

  sed 's/\<lambda\>/λ/g'


* The lambda keyword is quite long and distracts from the "meat" of the lambda expression. 
  Replacing it by a single-character keyword improves readability.

* The resulting code resembles more closely mathematical notation (in particular, lambda-calculus notation),
  so it brings Python closer to being "executable pseudo-code".

* The alternative spelling λ/lambda is quite intuitive (at least to anybody who knows Greek letters.)


For your convenience already noticed here:

* Introducing λ is introducing TIMTOWTDI.

* Hard to type with certain editors.
  But note that the old syntax is still available.
  Easy to fix by upgrading to VIM ;-) 

* Will turn a pre-existing legal identifier λ into a keyword.
  So backward-incompatible.

Needless to say, my personal opinion is that the advantages outweigh the disadvantages. ;-)