Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #83933

Re: lambdak: multi-line lambda implementation in native Python

Show all headers | View raw

In article <54ba39e0$0$13008$c3e8da3$5496439d@news.astraweb.com>,
 Steven D'Aprano <steve+comp.lang.python@pearwood.info> wrote:

> Every time I think I would like to learn a new language, I quite quickly run
> into some obvious feature that Python has but the newer language lacks, and
> I think "bugger this for a game of soldiers" and abandon it.

Wow.  Another wonderful English phrase to add to my vocabulary.  That's 
up there with Bob's your uncle :-)

> Ah, wait, I forgot Ruby's brilliant "feature" that whitespace *between*
> expressions is significant:
> 
> [steve@ando ~]$ cat ~/coding/ruby/ws-example.rb
> #!/usr/bin/ruby
> 
> def a(x=4)
>     x+2
> end
> 
> b = 1
> print "a + b => ", (a + b), "\n"
> print "a+b   => ", (a+b), "\n"
> print "a+ b  => ", (a+ b), "\n"
> print "a +b  => ", (a +b), "\n"
> 
> [steve@ando ~]$ ruby ~/coding/ruby/ws-example.rb
> a + b => 7
> a+b   => 7
> a+ b  => 7
> a +b  => 3
> 
> 
> A shiny new penny for any non-Ruby coder who can explain that!

The last time I looked at Ruby was when it was brand new.  I bought the 
original pickaxe book and read it on a plane trip.  It looked pretty 
cool at the time, but I never really got into it.  So I think I qualify.

Anyway, I'm going to guess from the above examples, that uttering a name 
means, "If the referent is callable, call it, if not, get its value".  
This is the same, for example, as django's template language.  Or, kind 
of like Python's properties.  So

(a + b)

means "Call a(), and add the value of b to that".  I'm going to further 
guess that

def a(x=4)

means a() takes an optional argument, with a default value of 4, just 
like in Python.  So

a

returns 6, i.e. 4 + 2.  I'm going to further guess that

(a +b)

is parsed as "call a, passing +b as an argument", and the "+" is taken 
as a unary prefix.

I want my penny.

This is not the only example of significant whitespace in programming 
languages.

Old-style C/C++ allowed either += or =+ for the increment operator.  
This led to parsing ambiguity for things like a=+b, where (IIRC), "a = 
+b" was parsed as an assignment and unary +, and "a =+ b" was parsed as 
an increment.  Eventually, the syntax was changed to make += the only 
legal way to write increment.

There was also the problem with nested template operators in C++, where 
"Foo<T1<T2>>" was mis-parsed, and you had to write it as "Foo <T1 <T2> 
>" (or something like that) to get it to parse right.

Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

lambdak: multi-line lambda implementation in native Python yawar.amin@gmail.com - 2015-01-14 21:54 -0800
  Re: lambdak: multi-line lambda implementation in native Python Steven D'Aprano <steve@pearwood.info> - 2015-01-15 06:06 +0000
    Re: lambdak: multi-line lambda implementation in native Python Ian Kelly <ian.g.kelly@gmail.com> - 2015-01-14 23:39 -0700
      Re: lambdak: multi-line lambda implementation in native Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-16 01:29 +1100
        Re: lambdak: multi-line lambda implementation in native Python Skip Montanaro <skip.montanaro@gmail.com> - 2015-01-15 08:38 -0600
      Re: lambdak: multi-line lambda implementation in native Python Yawar Amin <yawar.amin@gmail.com> - 2015-01-15 18:07 -0800
        Re: lambdak: multi-line lambda implementation in native Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-16 15:17 +1100
    Re: lambdak: multi-line lambda implementation in native Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-01-15 17:22 +0000
  Re: lambdak: multi-line lambda implementation in native Python Roy Smith <roy@panix.com> - 2015-01-15 08:04 -0500
    Re: lambdak: multi-line lambda implementation in native Python Chris Angelico <rosuav@gmail.com> - 2015-01-16 00:09 +1100
    Re: lambdak: multi-line lambda implementation in native Python Skip Montanaro <skip.montanaro@gmail.com> - 2015-01-15 07:11 -0600
      Re: lambdak: multi-line lambda implementation in native Python Marko Rauhamaa <marko@pacujo.net> - 2015-01-15 15:24 +0200
        Re: lambdak: multi-line lambda implementation in native Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-16 01:24 +1100
          Re: lambdak: multi-line lambda implementation in native Python Chris Angelico <rosuav@gmail.com> - 2015-01-16 01:50 +1100
          Re: lambdak: multi-line lambda implementation in native Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-01-15 19:47 -0500
            Re: lambdak: multi-line lambda implementation in native Python Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-01-17 00:21 +1300
              Re: lambdak: multi-line lambda implementation in native Python Marko Rauhamaa <marko@pacujo.net> - 2015-01-16 14:06 +0200
                Re: lambdak: multi-line lambda implementation in native Python Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-01-17 10:24 +1300
                Re: lambdak: multi-line lambda implementation in native Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-17 21:33 +1100
                Re: lambdak: multi-line lambda implementation in native Python alister <alister.nospam.ware@ntlworld.com> - 2015-01-17 18:30 +0000
        Re: lambdak: multi-line lambda implementation in native Python Roy Smith <roy@panix.com> - 2015-01-15 20:34 -0500
          Re: lambdak: multi-line lambda implementation in native Python Michael Torrie <torriem@gmail.com> - 2015-01-15 18:44 -0700
          Re: lambdak: multi-line lambda implementation in native Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-01-16 02:14 +0000
          Re: lambdak: multi-line lambda implementation in native Python Chris Angelico <rosuav@gmail.com> - 2015-01-16 15:00 +1100
            Re: lambdak: multi-line lambda implementation in native Python Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-01-17 10:29 +1300
              Re: lambdak: multi-line lambda implementation in native Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-17 21:30 +1100
                Re: lambdak: multi-line lambda implementation in native Python Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2015-01-17 12:49 +0200
                Re: lambdak: multi-line lambda implementation in native Python Marko Rauhamaa <marko@pacujo.net> - 2015-01-17 13:07 +0200
                Re: lambdak: multi-line lambda implementation in native Python Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2015-01-17 13:59 +0200
                Re: lambdak: multi-line lambda implementation in native Python Marko Rauhamaa <marko@pacujo.net> - 2015-01-17 14:15 +0200
                Re: lambdak: multi-line lambda implementation in native Python Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2015-01-17 14:54 +0200
                Re: lambdak: multi-line lambda implementation in native Python Skip Montanaro <skip.montanaro@gmail.com> - 2015-01-17 06:19 -0600
                Re: lambdak: multi-line lambda implementation in native Python Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2015-01-17 15:19 +0200
                Re: lambdak: multi-line lambda implementation in native Python Roy Smith <roy@panix.com> - 2015-01-17 12:24 -0500
                Re: lambdak: multi-line lambda implementation in native Python Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-01-18 11:41 +1300
                Re: lambdak: multi-line lambda implementation in native Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-17 23:48 +1100
                Re: lambdak: multi-line lambda implementation in native Python Roy Smith <roy@panix.com> - 2015-01-17 12:20 -0500
                Re: lambdak: multi-line lambda implementation in native Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-18 13:45 +1100
                Re: lambdak: multi-line lambda implementation in native Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-01-17 17:21 -0500
                Re: lambdak: multi-line lambda implementation in native Python Danilo Coccia <daniloco@acm.org> - 2015-01-17 15:20 +0100
                Re: lambdak: multi-line lambda implementation in native Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-17 23:49 +1100
                Re: lambdak: multi-line lambda implementation in native Python Chris Angelico <rosuav@gmail.com> - 2015-01-18 00:33 +1100
                Re: lambdak: multi-line lambda implementation in native Python Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-01-18 10:56 +1300
                Re: lambdak: multi-line lambda implementation in native Python Chris Angelico <rosuav@gmail.com> - 2015-01-18 09:04 +1100
                Re: lambdak: multi-line lambda implementation in native Python Roy Smith <roy@panix.com> - 2015-01-17 11:56 -0500
                Re: lambdak: multi-line lambda implementation in native Python Grant Edwards <invalid@invalid.invalid> - 2015-01-17 18:51 +0000
                Re: lambdak: multi-line lambda implementation in native Python Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-01-18 10:48 +1300
              Re: lambdak: multi-line lambda implementation in native Python Grant Edwards <invalid@invalid.invalid> - 2015-01-17 18:44 +0000
                Re: lambdak: multi-line lambda implementation in native Python Dan Sommers <dan@tombstonezero.net> - 2015-01-17 19:08 +0000
                Re: lambdak: multi-line lambda implementation in native Python alister <alister.nospam.ware@ntlworld.com> - 2015-01-17 20:22 +0000
          Factories and Builders [was Re: lambdak...] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-16 16:08 +1100
            Re: Factories and Builders [was Re: lambdak...] Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-01-17 10:25 +1300
          Re: lambdak: multi-line lambda implementation in native Python Ian Kelly <ian.g.kelly@gmail.com> - 2015-01-15 22:29 -0700
          Re: lambdak: multi-line lambda implementation in native Python Ethan Furman <ethan@stoneleaf.us> - 2015-01-15 21:42 -0800
          Re: lambdak: multi-line lambda implementation in native Python Michael Torrie <torriem@gmail.com> - 2015-01-16 09:23 -0700
  Re: lambdak: multi-line lambda implementation in native Python Rustom Mody <rustompmody@gmail.com> - 2015-01-15 09:19 -0800
    Re: lambdak: multi-line lambda implementation in native Python Yawar Amin <yawar.amin@gmail.com> - 2015-01-15 18:18 -0800
      Re: lambdak: multi-line lambda implementation in native Python Rustom Mody <rustompmody@gmail.com> - 2015-01-15 18:48 -0800
        Re: lambdak: multi-line lambda implementation in native Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-01-16 03:02 +0000
          Re: lambdak: multi-line lambda implementation in native Python Rustom Mody <rustompmody@gmail.com> - 2015-01-15 19:14 -0800
        Re: lambdak: multi-line lambda implementation in native Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-16 15:16 +1100
          Re: lambdak: multi-line lambda implementation in native Python Rustom Mody <rustompmody@gmail.com> - 2015-01-15 20:58 -0800
  Re: lambdak: multi-line lambda implementation in native Python Rick Johnson <rantingrickjohnson@gmail.com> - 2015-01-15 19:06 -0800
    Re: lambdak: multi-line lambda implementation in native Python Yawar Amin <yawar.amin@gmail.com> - 2015-01-15 19:20 -0800

csiph-web