[Python-ideas] allow `lambda' to be spelled λ

[tritium-list at sdamon.com]

For better or worse, except for string literals which can be anything as long as you set a coding comment, python is pure ascii which simplifies everything.  Lambda is not in the first 128 characters of Unicode, so it is highly unlikely to be accepted.

 

*         ‘Lambda’ is exactly as discouraging to type as it needs to be.  A more likely to be accepted alternate keyword is ‘whyareyounotusingdef’

*         Python doesn’t attempt to look like mathematical formula

*         ‘Lambda’ spelling is intuitive to most people who program

*         TIMTOWTDI isn’t a religious edict.  Python is more pragmatic than that.

*         It’s hard to type in ALL editors unless your locale is set to (ancient?) Greek.

*         …  What are you doing to have an identifier outside of ‘[A-Za-z_][A-Za-z0-9_]+’?

 

From: Python-ideas [mailto:python-ideas-bounces+tritium-list=sdamon.com at python.org] On Behalf Of Stephan Houben
Sent: Tuesday, July 12, 2016 8:38 AM
To: python-ideas at python.org
Subject: [Python-ideas] allow `lambda' to be spelled λ

 

Hi list,

 

Here is my speculative language idea for Python:

 

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

 

λ

 

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

 

Background:

 

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'

 

Advantages:

 

* 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.)

 

 

Disadvantages:

 

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. ;-)

 

Greetings,

 

Stephan

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-ideas/attachments/20160712/b26fabbc/attachment.html>