I really would be interested in your thoughts about this
a. in the context of your own projects, and
b. with regard to teaching programming newbies
The GitHub Ruby Styleguide [1] states: "The and and or keywords are banned. It's just not worth it. Always use && and || instead".
So what's your practice/recommendation:
1. use only &&, ||
2. use only `and', `or'
3. distinguish between boolean expressions (if this && that)
and control flow (loot = give_money or die)
4. ???
1. and 2. might require extra parentheses that often could be
avoided with 3., but using parentheses might be clearer anyway.
Especially for students who might have a hard time coping with
the different precedences.
I want to use a consistent style so I don't have to think about the precedences that much. This and the fact that I more frequently use && and || brings me to the conclusion that 1. is just more useful, because I have to write less parentheses which in turn make the code easier to read (at least imo). This also makes it easier to learn Ruby/programming for newbies.
Compare:
foo = hsh[:bar] || hsh[:alternative] || "" # I think lines like these are quite common, because many libraries like to use hashes as parameters and initialization like this is very expressive
to
foo = ( hsh[:bar] or hsh[:alternative] or "" ) # I think the additional parentheses just distract from what I want to accomplish, which is just an initialization. Parentheses to me always smell like complex computation (which this is not)
In my opinion using || in this case is more clear, because you can read the || as "or".
And one thing I want to add to your third proposed practice: In the case of "loot = give_money or die" I'd almost certainly think that the or is evaluated before the assignment (just because of the different precedences) at first.
Just my two cents.
Regards,
Calvin
···
On 05.01.2013 13:35, sto.mar@web.de wrote:
a. in the context of your own projects, and
b. with regard to teaching programming newbies
The GitHub Ruby Styleguide [1] states: "The and and or keywords are banned. It's just not worth it. Always use && and || instead".
So what's your practice/recommendation:
1. use only &&, ||
2. use only `and', `or'
3. distinguish between boolean expressions (if this && that)
and control flow (loot = give_money or die)
4. ???
Well, you might already be familiar with this, but this is what I use:
"Use &&/|| for boolean expressions, and/or for control flow. (Rule of
thumb: If you have to use outer parentheses, you are using the wrong
operators.)"
That's what I do. You've already been quoted the Ruby Style Guide, so
that leaves using the verbal versions for control flow. I've tried to
get used to that, and frankly it just doesn't seem anywhere near as
clear as "if this_fails do_that". Using and/or for control flow is a
popular idiom in Perl, but that doesn't say anything about its clarity
(at least, anything positive), which is very important to Rubyists.
-Dave
···
On Sat, Jan 5, 2013 at 7:35 AM, <sto.mar@web.de> wrote:
The GitHub Ruby Styleguide [1] states: "The and and or keywords are banned.
It's just not worth it. Always use && and || instead".
--
Dave Aronson, the T. Rex of Codosaurus LLC,
secret-cleared freelance software developer
taking contracts in or near NoVa or remote.
See information at http://www.Codosaur.us/\.
This can help you: http://rubylearning.com/images/operators.jpg
It's the ruby operators by relevance, very usefull for beginners to
understand how to work without parentheses(although not recommended).
And also to know which or not is a method. See you around.
I use and/or for logical expressions and &&/|| for technical stuff like
default values. I never use any of them for control flow, because that's
just too much magic. Especially since if/unless modifiers are just as
compact and much clearer.
Personally, I hate &&/|| in "if" statements. This is not C or Java! We
have actual English words for that, not those ugly leftovers from
ancient times where people thought bit operators were more important
then logical expressions.
And how is the low precendence of and/or "dangerous"? Isn't that exactly
what you want in an "if" statement? To have the logical operators
executed at the very end?
3 - for both. Why should I recommend teaching a practice I don't
follow. Then I'd rather explain only "&&" and "||", mention that
there are also other boolean operators but that I'll cover them later
in the tutorial etc.
Kind regards
robert
···
On Sat, Jan 5, 2013 at 1:35 PM, <sto.mar@web.de> wrote:
So what's your practice/recommendation:
1. use only &&, ||
2. use only `and', `or'
3. distinguish between boolean expressions (if this && that)
and control flow (loot = give_money or die)
4. ???
I think I'm in the minority here, so I'll give my minority opinion: For my own projects I prefer and/or and only use &&/|| for assignments. Looking through one of my codebases, I see 312 uses of "and" and 8 uses of "&&" (mostly from other contributors).
Why? Because I also dislike using parentheses for method calls, which again seems to be becoming a minority preference. (Also, by default vim highlights and/or but not &&/|| and I like pretty colors.)
irb(main):001:0> def x *args; true; end
=> nil
irb(main):002:0> def y *args; true; end
=> nil
irb(main):003:0> if x 1 and y 2
irb(main):004:1> puts "all good"
irb(main):005:1> end
all good
=> nil
irb(main):006:0> if x 1 && y 2
irb(main):007:1> puts "not all good"
irb(main):008:1> end
SyntaxError: (irb):6: syntax error, unexpected tINTEGER, expecting keyword_do or '{' or '('
(irb):8: syntax error, unexpected keyword_end, expecting $end
from /home/justin/.rvm/rubies/ruby-1.9.3-p327/bin/irb:12:in `<main>'
I haven't spent much time teaching others, so I don't really have an opinion on that. I assume those coming from other languages would be more comfortable with &&/||.
I also prefer to use "not" because that stands out more to me than "!".
-Justin
···
On 01/05/2013 04:35 AM, sto.mar@web.de wrote:
Hi group,
I really would be interested in your thoughts about this
a. in the context of your own projects, and
b. with regard to teaching programming newbies
The GitHub Ruby Styleguide [1] states: "The and and or keywords are
banned. It's just not worth it. Always use && and || instead".
So what's your practice/recommendation:
1. use only &&, ||
2. use only `and', `or'
3. distinguish between boolean expressions (if this && that)
and control flow (loot = give_money or die)
4. ???
1. and 2. might require extra parentheses that often could be
avoided with 3., but using parentheses might be clearer anyway.
Especially for students who might have a hard time coping with
the different precedences.
I really would be interested in your thoughts about this
a. in the context of your own projects, and
b. with regard to teaching programming newbies
The GitHub Ruby Styleguide [1] states: "The and and or keywords are
banned. It's just not worth it. Always use && and || instead".
Thanks to all for your interesting input.
To sum up: I have come to the conclusion to ban 'and'/'or' completely
In the limited time I have I can only discuss a small subset
of the Ruby language anyway, and flow control with 'and'/'or'
rather falls in the category of syntactic sugar, especially for
a beginner.
I have been confirmed in the believe that 'and'/'or' for logical
expressions -- though very readable -- is just BAD and dangerous,
because the behavior is too surprising.
A student (and maybe not only a student) might happily refactor
if cond1 and cond2
...
end
to
condition = cond1 and cond2
if condition
...
end
without ever noticing that this would break the logic of the code.
I still might use 'and'/'or' for flow control in my personal projects,
but I use this idiom very seldom anyway and rather prefer if/unless.
Regards,
Marcus
···
Am 05.01.2013 13:35, schrieb sto.mar@web.de:
from my teaching (except for mentioning their existence).
So what's your practice/recommendation:
1. use only &&, ||
2. use only `and', `or'
3. distinguish between boolean expressions (if this && that)
and control flow (loot = give_money or die)
4. ???
1. and 2. might require extra parentheses that often could be
avoided with 3., but using parentheses might be clearer anyway.
Especially for students who might have a hard time coping with
the different precedences.
Maybe(?) worth mentioning that the Github Ruby Styleguide, though based
on the guide cited by you, explicitly differs in this point.
···
Am 05.01.2013 17:25, schrieb Joel Pearson:
Well, you might already be familiar with this, but this is what I use:
"Use &&/|| for boolean expressions, and/or for control flow. (Rule of
thumb: If you have to use outer parentheses, you are using the wrong
operators.)"
I do understand their different precedence, that was not the point
at all. But thanks anyway.
···
Am 05.01.2013 22:57, schrieb Damián M. González:
This can help you: Learn How to Blog and Build Websites for Profit!
It's the ruby operators by relevance, very usefull for beginners to
understand how to work without parentheses(although not recommended).
And also to know which or not is a method. See you around.
On Sat, Jan 5, 2013 at 7:35 AM, <sto.mar@web.de> wrote:
The GitHub Ruby Styleguide [1] states: "The and and or keywords are banned.
It's just not worth it. Always use && and || instead".
That's what I do. You've already been quoted the Ruby Style Guide, so
that leaves using the verbal versions for control flow. I've tried to
get used to that, and frankly it just doesn't seem anywhere near as
clear as "if this_fails do_that". Using and/or for control flow is a
popular idiom in Perl, but that doesn't say anything about its clarity
(at least, anything positive), which is very important to Rubyists.
-Dave
There's only one time I can think of where I use "or" for the sake of
readability. I'll often have a main method call a series of other
methods, each of which returns a boolean, and sets the error level as a
way of reporting failure. That is then passed to the errorhandler. This
leads to some simple lines like this:
Consider the difference between "x = true && false" and "x = true and
false". Since && has HIGHER precedence than =, "x = true && false" is
equivalent to "x = (true && false)", just as you might expect. The
whole expression (including the assignment) evaluates to false, and x
is assigned false. No problem. But since "and" has LOWER precedence
than =, "x = true and false" is equivalent to "(x = true) and false".
You smell something wrong already, don't you? The whole expression
(including assignment) evaluates to false again... but lo and behold,
x is true! That's because you've left the boolean operators wait
until the end, as you believe might be so harmless.
The analogous situation for || versus "or" is left as an exercise for
the reader.
BTW, these two were already part of a talk I've been working on, on
Ruby Gotchas, coming soon to a RUG near you. Well, at least near me.
-Dave
···
On Sat, Jan 5, 2013 at 5:46 PM, Jan E. <lists@ruby-forum.com> wrote:
And how is the low precendence of and/or "dangerous"? Isn't that
exactly what you want in an "if" statement? To have the logical
operators executed at the very end?
--
Dave Aronson, the T. Rex of Codosaurus LLC,
secret-cleared freelance software developer
taking contracts in or near NoVa or remote.
See information at http://www.Codosaur.us/\.
Jan, I am not totally sure what you mean by this. In any case (&& or
and) the left expression is evaluated before the operator and operator
and boolean result of that left expression evaluation determine
whether the right hand expression is evaluated _at all_.
Precedence only indirectly affects execution order by means of
grouping of expressions.
Kind regards
robert
···
On Sat, Jan 5, 2013 at 11:46 PM, Jan E. <lists@ruby-forum.com> wrote:
And how is the low precendence of and/or "dangerous"? Isn't that exactly
what you want in an "if" statement? To have the logical operators
executed at the very end?
1. use only &&, ||
2. use only `and', `or'
3. distinguish between boolean expressions (if this && that)
and control flow (loot = give_money or die)
4. ???
3 - for both. Why should I recommend teaching a practice I don't
follow.
Because beginners (in my case high school students with zero programming
experience) are lacking the knowledge and experience you have.
They might be completely unable to grasp and especially internalize
the subleties and gotchas that are involved here.
Then I'd rather explain only "&&" and "||", mention that
there are also other boolean operators but that I'll cover them later
in the tutorial etc.
Exactly. This discussion has confirmed my tendency to only teach
&&, || (for boolean expressions, assignments with defaults, ...)
and leave control flow to if/unless.
Myself, I use constructs like `do_something or do_other'
very seldom anyway.
···
Am 06.01.2013 17:47, schrieb Robert Klemme:
On Sat, Jan 5, 2013 at 1:35 PM, <sto.mar@web.de> wrote:
I could not write that line and still sleep at night...
···
Am 07.01.2013 03:34, schrieb Justin Collins:
Why? Because I also dislike using parentheses for method calls, which
again seems to be becoming a minority preference. (Also, by default vim
highlights and/or but not &&/|| and I like pretty colors.)
irb(main):001:0> def x *args; true; end
=> nil
irb(main):002:0> def y *args; true; end
=> nil
irb(main):003:0> if x 1 and y 2
This is a *very* good point -- one which I had not considered. Even if
*I* understand how they work, the next person (or n-th person) looking
at my code might not. Now I really do understand the choice in the
style guide. I personally have not used and/or in if/unless
statements; I've only used them for control. But now I'm finding using
if/unless to manage the control much clearer, and using and/or in that
way does begin to seem more like a side-effect. I'm joining the ban
the and crowd.
···
On Fri, Jan 11, 2013 at 10:34 AM, <sto.mar@web.de> wrote:
A student (and maybe not only a student) might happily refactor
if cond1 and cond2
...
end
to
condition = cond1 and cond2
if condition
...
end
without ever noticing that this would break the logic of the code.
Well, you might already be familiar with this, but this is what I use:
"Use &&/|| for boolean expressions, and/or for control flow. (Rule of
thumb: If you have to use outer parentheses, you are using the wrong
operators.)"
Consider the difference between "x = true && false" and "x = true and
false". Since && has HIGHER precedence than =, "x = true && false" is
equivalent to "x = (true && false)", just as you might expect.
Why would I expect that? Why would I even *use* assignments in "if"
statements?
Sorry, but if you use assignments in "if" statements (much too obscure)
without explicit parenthesis (even worse), then I'd say *this* is your
problem, not the implicit operator precedence you somehow consider to be
"wrong".
Maybe my programming style is totally out of fashion, but my "if"
statements usually look like this:
if <some expression> and (<some expression> or <some expression>)
...
end
With <some expression> being a pure expression (no change of state). In
that context, I want a very low precedence to make sure that each <some
is evaluated *before* and/or takes action.
And I believe this is the sane way of writing "if" statements.
When I want to do "magic" like
var = val || alt
then I do use &&/||. But this is a very different context.
There is already too much written about using return values for error
handling. So I'll only say that I don't think this kind of design is
good.
Kind regards
robert
···
On Sat, Jan 5, 2013 at 11:29 PM, Joel Pearson <lists@ruby-forum.com> wrote:
There's only one time I can think of where I use "or" for the sake of
readability. I'll often have a main method call a series of other
methods, each of which returns a boolean, and sets the error level as a
way of reporting failure. That is then passed to the errorhandler. This
leads to some simple lines like this:
