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7 points by mdemare 6119 days ago | link | parent

To sum up, Arc wins once, draws three times and loses six times (counting tokens, not characters).

I think the goal for Arc should be to be powerful enough to express all these cases without resorting to expressions (+ - len).

Most obvious improvement - allow negative indices for the second argument. Then you could say:

    (cut s -x)
for

    s[-x .. -1]
Right now, Ruby just has more syntax to express this, e.g. four different forms:

    s[x] ; s[i,j] ; s[i .. j] ; s[i ... j]
Arc only has three:

    (s x) ; (cut s x) ; (cut s i j)


7 points by steadicat 6119 days ago | link

Python only has two forms (s[x] ; s[i:j]), yet it can express the same things more succinctly: see below.

I find Python's model vastly superior. Less syntax to learn, yet more powerful.

Here is the comparison with Python added in as the first one:

The i'th item of s

    s[i]
    s[i]
    (s i)
The i'th item of s from the end

    s[-i]
    s[-i]
    (s (- (len s) i))
The first x items of s

    s[:x]
    s[0,x]
    (cut s 0 x)
The last x items of s

    s[-x:]
    s[-x..-1]
    (cut s (- (len s) x))
The items from position i to the end

    s[i:]
    s[i .. -1]
    (cut s i)
The items from position i to position j (inclusive)

    s[i:j+1]
    s[i .. j]
    (cut s i (+ 1 j))
The items from position i to position j (exclusive)

    s[i:j]
    s[i ... j]
    (cut s i j)
i items beginning at position j.

    s[j:j+i]
    s[j,i]
    (cut s j (+ i j))
The items from position i to the end minus the last j items

    s[i:-j]
    s[i ... -j]
    (cut s i (- -1 j))
i items beginning at the j'th position from the end

    s[-j:-j+i]
    s[-j,i]
    (cut s (- (len s) j) (+ (- (len s) j) i))

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2 points by vrk 6119 days ago | link

For reference, here's how you can do it in Perl 5:

The ith item of s:

  $s[i]
The ith item of s from the end:

  $s[-i]
The first x items of s:

  @s[0 .. x-1]
The last x items of s:

  @s[-x .. -1]
The items from position i to the end:

  @s[i .. $#s]
The items from position i to position j (exclusive):

  @s[i .. j-1]
i items beginning at position j:

  @s[j .. j+i]
The items from position i to the end minus the last j items:

  @s[i .. $#s-j]
  # Alternative:
  (@s[i .. $#s])[0 .. j-1]
i items beginning at the jth position from the end:

  @s[-j .. -j-i]
  # Alternative:
  (@s[-j .. -1])[0 .. i-1]
Legend:

  $s[i]  # A scalar at index i
  @s[<something complex>]  # An array slice (i.e. multiple values)
  $#s  # The last index of the array s
  a .. b  # In list context, a list of numbers or letters from a to b, inclusive (can be used outside array indexing)

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4 points by pg 6119 days ago | link

If you're comparing for length, at least use dot notation.

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6 points by steadicat 6119 days ago | link

I think the key point is that Ruby's power can be achieved with less syntax forms without compromises.

The fact that Python's way also happens to be shorter is not the main point, just an added plus.

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2 points by jules 6119 days ago | link

Are you aware that x..y and x...y notation is a Range literal in Ruby? I like Pythons syntax better but range notation isn't special syntax for slices.

obj[a,b,...] is sugar for a method call in Ruby (you can define a [] method for your own classes). So there's really only two syntactic forms here, and arguably no special syntax for slices.

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1 point by mdemare 6119 days ago | link

I'm counting each occurrence of i,j and x, each occurrence of 1, and each occurrence of len, + and (binary) -.

That yields the following scores: Python : 1 1 1 1 1 4 2 4 2 4 => 21 Ruby : 1 1 2 2 2 2 2 2 2 2 => 18 Arc : 1 3 2 3 1 4 2 4 4 8 => 32

15 is the best possible score. This is meant as succinctness benchmark for the index and slice/cut operations, which are extremely common.

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1 point by jc 6110 days ago | link

I think there's a reccuring mistake in the arc snippet for "The items from position i to the end minus the last j items."

I think it should be

  (cut s i -j)
... but I know I could be missing something

(thanks for the help, cadaver)

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1 point by cadaver 6110 days ago | link

Have a look at the little "help" next to the "about" box in your profile.

Also, I noticed that some people use a single ' to quote a function name on its own within a sentence (just like in Arc).

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