Describe the bug
2015:9 gives "Internal error – No result was provided when the context expected one "

To Reproduce
Steps to reproduce the behavior:

1. Go to 2015:9
2. Enter anything into the input box
3. Open console and enter debug=true
4. Submit and see error ¯315 Internal error – No result was provided when the context expected one

Can't use all the primitives 😢

Should be "ravel"

Is your feature request related to a problem? Please describe.
A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]

Describe the solution you'd like
A clear and concise description of what you want to happen.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
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There is an unclosed span tag in the description for problem 2021/10:

returns a right-aligned character array R«/span> of shape

Missing ⍥ and ⍤ is Rank only.

Put ⎕OFF in the input field and run it.
Inconsistent odd errors

Describe the bug

Task states:

Write a function that takes a numeric vector as its right argument and returns the median of the array. 

but the last example is:

your_function 7 
7

Expected behavior

Either change the task description to include ...or numeric scalar, or change the last example so that the right argument is a vector:

    your_function ,7 
    7

Enter {∧/(0∘≤∧2∘>)+\-⌿'<>'∘.=⍵} into https://problems.tryapl.org/psets/2018.html?goto=P6_Whats_Your_Angle

Describe the bug
test button for problem solution is unresponsive, for most problems

Desktop (please complete the following information):

• OS: Debian 12
• Browser: Firefox

Otherwise, thanks for the cool website. It is helping me to learn APL

For P1 from 2018, "Oh Say Can You See", the output is defined as

[...] an integer representing the number of skyscrapers that can be seen.

However, the test cases expect a 1-item vector.
I would like to know if the output should have been specified as a 1-item vector, or if the validator should be lenient (and how lenient) before committing a fix in a PR.

Opening the website on mobile devices we see the problem descriptions get squashed horizontally, making them take too much vertical space.

To Reproduce
Open problems.tryapl.org on a mobile device.

Screenshots

Smartphone

• Device: MI 8
• OS: Android 10;
• Browser Chrome 85.0
  (And also on an iPhone 6, Safari)

Describe the bug

Second example claims that:

'Dyalog' your_function 'APL'   
DAaPlLog

This is incorrect (it can be seen that the result lacks the y in Dyalog). It should be DAyPaLlog

https://problems.tryapl.org/psets/2019.html?goto=P4_Knight_Moves

numbers appear vertically stacked

To Reproduce
Steps to reproduce the behavior:

1. Go to https://problems.tryapl.org/
2. Scroll down to sample problem input
3. Try {⎕←'ok'}¨

We should probably suppress ⎕ and ⍞ output if possible, but it's low priority (anyone who knows what ⎕ and ⍞ do should be able to figure out what's going on)

Describe the solution you'd like
Ctrl+Enter should have the same effect as clicking the run button in a question.

A feature that is common on many runner websites and is purely for convenience.

Describe the bug
One of the tests results in the following:

Result should have been (1) with ('T') as right argument 

which is clearly at odds with the example text for

your_function 'G'
0 0 1 0

To Reproduce
Steps to reproduce the behavior:

Try {+/(,⍵)=⍤1 0⊢'ACGT'}

Expected behavior

The correct result is 0 0 0 1 for a right argument of T.

Desktop (please complete the following information):

• OS: MacOS 11.6 Big Sur
• Browser: Firefox
• Version: 92.0

https://problems.tryapl.org/psets/2013.html

reported by @bpbecker

Describe the bug

2020 p10:

{⍉¯1↓1↓⍉⍕⍪⍕¨⍵}

passes with flying colours, but does not give the expected result for the last example:

      {⍉¯1↓1↓⍉⍕⍪⍕¨⍵},'A'
┌⊖┐
↓ │
└─┘

Expected behavior

Either the solution is incorrect, or the example text is wrong, or a test case is missing.

Desktop (please complete the following information):

• OS: MacOS
• Browser: Firefox
• Version: 89.0.2

Describe the bug

Message:

Result should have been (1 9 2⍴2 1 3 2 4 3 5 4 6 5 7 4 8 3 9 2 10 1) with (2⍴5) as right argument 

is the wrong shape, given instruction returns a 2 column matrix. Shape should be 9 2.

To Reproduce

Steps to reproduce the behavior -- I tried {{⍺,≢⍵}⌸∊⊃∘.+/⍳¨,⍵}

Expected behavior

The dfn {{⍺,≢⍵}⌸∊⊃∘.+/⍳¨,⍵} produces the correct result shape for a right arg of 5 5:

      {{⍺,≢⍵}⌸∊⊃∘.+/⍳¨,⍵} 5 5
┌→───┐
↓ 2 1│
│ 3 2│
│ 4 3│
│ 5 4│
│ 6 5│
│ 7 4│
│ 8 3│
│ 9 2│
│10 1│
└~───┘

The main web page has a clickable legend at the top of the page so that APL characters can easily be entered

-but- that legend is too far from the location where the characters are pasted in...

I'd suggest repeating that legend just above the area at the bottom of the page where user's can test their solution.

Describe the bug

A vector with only spaces should not return an empty numeric vector, but an empty char vector

To Reproduce
Steps to reproduce the behavior:

E.g. APL Cart's ' '∘(1↓,(/⍨)1(⊢∨⌽)0,≠) results in:

Passed all basic tests – for extra points, consider cases like ('') as right argument which should give (⍬)

Expected behavior

For the empty cases, '' and ' ' , the expected result should be 0⍴'', not 0⍴0.

Describe the bug

The reference solution to 2018/3 fails with the following error:

Internal error – reference solution caused DOMAIN ERROR with (⍬) as right argument 

(for any input).

The reference solution appears to be:

{{⍺('*'⍴⍨≢⍵)}⌸⊃(,∘.+)/⍳¨⍵}

which indeed fails for ⍬:

      {{⍺('*'⍴⍨≢⍵)}⌸⊃(,∘.+)/⍳¨⍵} ⍬
DOMAIN ERROR
      {{⍺('*'⍴⍨≢⍵)}⌸⊃(,∘.+)/⍳¨⍵}⍬

I'd propose an alternative solution:

      {{⍺('*'/⍨≢⍵)}⌸+/¨,⍳⍵}⍬
0  *

Enter ⊢ into https://problems.tryapl.org/psets/2018.html?goto=P6_Whats_Your_Angle

Describe the bug

In the examples it is claimed that:

your_function 5 3⍴⍳15     ⍝ and average the rows of a matrix

7 8 9

A 5×3 matrix has 5 rows. The comment should say

⍝ and averages the cols of a matrix