Re: Command Languages Versus Programming Languages

On 03/04/2024 02:23, Lawrence D'Oliveiro wrote:

On 2 Apr 2024 08:26:14 GMT, Stefan Ram wrote:
 

ram@zedat.fu-berlin.de (Stefan Ram) wrote or quoted:
>

def diff( x ):
    return 1 if x == 'x' else 0 if type( x )is str else[ 'sum', diff( x[
    1 ]), diff( x[ 2 ])]
    if x[ 0 ]== 'sum' else None

>
   Oops! That was one long line starting with "return";
   it was wrapped by the newsreader, but is not correct Python anymore
   when wrapped this way.

 It’s bloody horrible Python even when wrapped correctly. I think Python’s
version of the conditional expression is a complete abortion.
 

That's probably the reason almost no one uses it.  That post is the first time I have ever seen conditional expressions outside of a brief mention in a tutorial on Python conditionals showing how to write normal conditionals in the language.  I think Python stole this one from Perl.

How about this, to at least get things the same way round as in the more
usual C-style conditional expression:
 def diff(x) :
     return \
         [
             lambda :
                 [
                     lambda :
                         [
                             lambda : None,
                             lambda : ['sum', diff(x[1]), diff(x[2])],
                         ][x[0] == 'sum'](),
                     lambda : 0,
                 ][isinstance(x, str)](),
             lambda : 1,
         ][x == 'x']()
#end diff

How about just writing Python code the way pretty much everyone else writes Python code?  In a simple and obvious manner :
def diff(x) :
if x == 'x' :
return 1
if isinstance(x, str) :
return 0
if x[0] == 'sum' :
return ['sum', diff(x[1]), diff(x[2])]
return None