Yoda Conditions

Post by YSFEJ4SWJUVU6 » Fri, Feb 17, 2017, 6:23 PM UTC

selfsimilar wrote: post #13

In PHP I like using Yoda Conditions because there's a common idiom of testing assignment in the conditional: if ($value = getSomeValue()) { // Safely use value } Yoda Conditions defend nicely against accidents when '=' and '==' can be used legally this way and honestly you get used to reading them pretty quick.

  if (auto val = getval())
    foo(val); // executed only if getval() returned something that evaluates to true
              // in a boolean context

  if (var $val = getval()) {}

Post by kbenson » Fri, Feb 17, 2017, 6:36 PM UTC

dbaupp wrote: post #50

kbenson wrote: post #26

Earlier quoted context omitted.

There are useful cases for this. It's much less ambiguous in those cases if your language allows the definition of the variable in the same location, and scopes it. For example, Perl: use strict; use warnings; sub one { 1 } if ( my $one = one() ) { say $one; # prints 1 } say $one; # compilation error, "Global symbol "$one" requires explicit package name" This case is trivial, but when you want a temporary variable an…

Declaration and a (mutating) assignment are different: your example demonstrates that Perl signals the declaration with `my`, and other languages offer similar things like `if let ... = ... { ... }`

Post by devy » Fri, Feb 17, 2017, 6:57 PM UTC

paol wrote: post #3

Don't do this. In languages where accidental assignment is possible (i.e. writing if(a=b) when you meant if(a==b) ), configure the compiler or linter to emit a warning in this situation. For example in C, GCC will complain about this when compiling with -Wall, which you should be using anyway.

Post by kbenson » Fri, Feb 17, 2017, 7:23 PM UTC

kentt wrote: post #36

nayuki wrote: post #22

I would say that the phrase "Yoda conditions" more appropriately describes Ruby's alternative form of if-statements: if x > 0: y += x versus y += x if x > 0

One of the worst parts of Ruby. I can see the argument that it could be better to have save if valid rather than if valid save end but what I see 9 times out of 10 is things.do each |thing| foo bar baz end if valid or really.long.thing.that.i.try.to.parse.in.my.head if acutally_almost_never_happens which is harder to read since I read top to bottom / left to right, but the flow is bottom to top and right to left

    # Not allowed
    for ( 1 .. 10 ) {
        say $_;
    } if 1;
    
    # Allowed
    map { say $_ } ( 1 .. 10 ) if 1;

    # Not allowed
    { say "foo"; say $_ } for ( 1 .. 10 );
    
    # Allowed
    say $_ for ( 1 .. 10 );

    my %data = get_data_record_hash("foo");
    
    $data{$_} = update_field(data{$_}) for ('field1','field4',other_field');
    
    # Compare to map, which normally you expect to return values
    map { $data{$_} = update_field(data{$_}) } ('field1','field4',other_field');

Post by brianwawok » Fri, Feb 17, 2017, 7:29 PM UTC

megawatthours wrote: post #39

brianwawok wrote: post #6

Earlier quoted context omitted.

Eh, I think it is good in Java in cases where Null input is possible.

I never got the Java argument. I would much rather fail early and noisily with an NPE than return false and let my program happily chug along when it wasn't expecting a null. If the value is intended to be nullable, I would use an optional.