The `*` operator as used in Ruby. So called because it looks like an insect that's splatted on a windscreen.
The * operator as used in Ruby. So called because it looks like an insect that's splatted on a windscreen.
Questions tagged [splat]
166 questions
13
votes
1 answer
What is the difference between these two Ruby symbols?
I discovered this after playing around with object ids.
ObjectSpace._id2ref(2648)
=> :**
ObjectSpace._id2ref(6688)
=> :**
ObjectSpace._id2ref(2648) == ObjectSpace._id2ref(6688)
=> false
The first one is the symbol for the exponentiation…
Alex Altair
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13
votes
4 answers
How to set a default value for a splat argument in Ruby
Setting a default value for a splat argument gives an error:
1.9.3-p374 :001 > def a b, *c = nil
1.9.3-p374 :002?> end
SyntaxError: (irb):1: syntax error, unexpected '=', expecting ';' or '\n'
def a b, *c = nil
^
from…
jordanpg
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12
votes
5 answers
Why invoke "apply" instead of calling function directly?
When looking at the source code for raphael or g.raphael or other libraries I've noticed the developer does something like this:
var val = Math.max.apply(Math, data_array);
Why not just invoke the function directly, such as:
var val =…
codecraig
- 3,118
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12
votes
1 answer
Best way to document "splatted" parameter with YARD?
I have a method that should take 1+ parameters of any class, similar to Array#push:
def my_push(*objects)
raise ArgumentError, 'Needs 1+ arguments' if objects.empty?
objects.each do |obj|
puts "An object was pushed: #{obj.inspect}"
…
hololeap
- 1,156
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12
votes
1 answer
Explanation of splat
While reading about Julia on http://learnxinyminutes.com/docs/julia/ I came across this:
# You can define functions that take a variable number of
# positional arguments
function varargs(args...)
return args
# use the keyword return to…
kip820
- 305
- 3
- 6
12
votes
1 answer
Splat on a hash
A splat on a hash converts it into an array.
[*{foo: :bar}] # => [[:foo, :bar]]
Is there some hidden mechanism (such as implicit class cast) going on here, or is it a built-in primitive feature?
Besides an array, are nil and hash the only things…
sawa
- 165,429
- 45
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11
votes
1 answer
Understanding ruby splat in ranges and arrays
I'm trying to understand the difference between *(1..9) and [*1..9]
If I assign them to variables they work the same way
splat1 = *(1..9) # splat1 = [1, 2, 3, 4, 5, 6, 7, 8, 9]
splat2 = [*1..9] # splat2 = [1, 2, 3, 4, 5, 6, 7, 8, 9]
But things…
Dty
- 12,253
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10
votes
1 answer
Unroll / splat arguments in common lisp
Say I have a list of arguments:
> (setf format-args `(t "it's ~a" 1))
(T "it's ~a" 1)
How can I then "splat" or "unroll" this into a series of arguments rather than a single list argument, for supplying to the format function?
i.e I would like…
gfxmonk
- 8,614
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10
votes
2 answers
Double-splat operator destructively modifies hash – is this a Ruby bug?
I noticed what I find to be a very surprising behavior with the ** (double-splat) operator in Ruby 2.1.1.
When key-value pairs are used before a **hash, the hash remains unmodified; however, when key-value pairs are only used after the **hash, the…
user513951
- 12,445
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10
votes
5 answers
How to define a method in ruby using splat and an optional hash at the same time?
I am able to define a method like this:
def test(id, *ary, hash_params)
# Do stuff here
end
But this makes the hash_params argument mandatory. These don't work either:
def t(id, *ary, hash_params=nil) # SyntaxError: unexpected '=', expecting…
andersonvom
- 11,701
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9
votes
2 answers
Why do Ruby procs/blocks with splat arguments behave differently than methods and lambdas?
Why do Ruby (2.0) procs/blocks with splat arguments behave differently than methods and lambdas?
def foo (ids, *args)
p ids
end
foo([1,2,3]) # => [1, 2, 3]
bar = lambda do |ids, *args|
p ids
end
bar.call([1,2,3]) # => [1, 2, 3]
baz = proc do…
Jordan
- 391
- 4
- 12
9
votes
1 answer
Parentheses in block variables
Given
a = [[:a, :b, :c]]
1) I understand this
a.each{|(x, y), z| p z} # => :b
that there are two variables (x, y) and z, so the third element :c is thrown away, and z matches :b. And I understand this
a.each{|(x, y), z| p y} # => nil
that (x, y)…
sawa
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9
votes
2 answers
CoffeeScript: Expand array in function call
In Ruby I can call methods with array elements used as positional parameters like this
method(fixed_arg1, fixed_arg2, *array_of_additional_args)
Here the "*" operator expands the array in place.
I'm trying to do the same in CoffeeScript, but…
Michael Schuerig
- 137
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8
votes
2 answers
Ruby, Source Code of Splat?
Someone asked about the splat operator yesterday, and I wanted to see the source code... would that be written in C or in Ruby? Where would it be found?
Dan Rosenstark
- 68,471
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8
votes
3 answers
What does the syntax [*a..b] mean in Ruby?
NOTE: mischa's splat on GitHub has lots of cool interactive examples of * in action.
By googling, I found that one way to iterate over a range of numbers in Ruby (your classic C-style for loop)
for (i = first; i <= last; i++) {
whatever(i);
}
is…
Justin Force
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