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Attributes R←{X} ⎕AT Y

Y can be a simple character scalar, vector or matrix, or a vector of character vectors representing the names of 0 or more defined functions or operators. Used dyadically, this function closely emulates the APL2 implementation. Used monadically, it returns information that is more appropriate for Dyalog APL.

Y specifies one or more names. If Y specifies a single name as a character scalar, a character vector, or as a scalar enclosed character vector, the result R is a vector. If Y specifies one or more names as a character matrix or as a vector of character vectors R is a matrix with one row per name in Y.

Monadic Use

If X is omitted, R is a 4-element vector or a 4 column matrix with the same number of rows as names in Y containing the following attribute information:

R[1] or R[;1]: Each item is a 3-element integer vector representing the function header syntax:

1 Function result 0 if the function has no result 1 if the function has an explicit result ¯1 if the function has a shy result
2 Function valence 0 if the object is a niladic function or not a function 1 if the object is a monadic function 2 if the object is a dyadic function ¯2 if the object is an ambivalent function
3 Operator valence 0 if the object is not an operator 1 if the object is a monadic operator 2 if the object is a dyadic operator

The following values correspond to the syntax shown alongside: 

        0  0  0     ∇ FOO
        1  0  0     ∇ Z←FOO
       ¯1  0  0     ∇ {Z}←FOO
        0 ¯2  0     ∇ {A} FOO B
       ¯1  1  2     ∇ {Z}←(F OP G)B

R[2] or R[;2]: Each item is the (⎕TS form) timestamp of the time the function was last fixed.

R[3] or R[;3]: Each item is an integer reporting the current ⎕LOCK state of the function:

0 Not locked
1 Cannot display function
2 Cannot suspend function
3 Cannot display or suspend

R[4] or R[;4]: Each item is a character vector - the network ID of the user who last fixed (edited) the function.

Example

    ∇ {z}←{l}(fn myop)r
[1]   ...

    ∇ z←foo
[1]   ...

    ∇ z←{larg}util rarg
[1]   ...

      ⎕LOCK'foo'

      util2←util

      ]display ⎕AT 'myop' 'foo' 'util' 'util2'
.→--------------------------------------------.
↓ .→------. .→-----------------.     .→---.   |
| |¯1 ¯2 1| |1996 8 2 2 13 56 0|   0 |john|   |
| '~------' '~-----------------'     '----'   |
| .→----.   .→------------.          .⊖.      |
| |1 0 0|   |0 0 0 0 0 0 0|        3 | |      |
| '~----'   '~------------'          '-'      |
| .→-----.  .→------------------.    .→---.   |
| |1 ¯2 0|  |1996 3 1 14 12 10 0|  0 |pete|   |
| '~-----'  '~------------------'    '----'   |
| .→-----.  .→-------------------.   .→-----. |
| |1 ¯2 0|  |1998 8 26 16 16 42 0| 0 |graeme| |
| '~-----'  '~-------------------'   '------' |
'∊--------------------------------------------'

Dyadic Use

The dyadic form of ⎕AT emulates APL2. It returns the same rank and shape result containing information that matches the APL2 implementation as closely as possible.

The number of elements or columns in R and their meaning depends upon the value of X which may be 1, 2, 3 or 4.

If X is 1, R specifies valences and contains 3 elements (or columns) whose meaning is as follows:

1 Explicit result 1 if the object has an explicit result or is a variable 0 otherwise
2 Function valence 0 if the object is a niladic function or not a function 1 if the object is a monadic function 2 if the object is an ambivalent function
3 Operator valence 0 if the object is not an operator 1 if the object is a monadic operator 2 if the object is a dyadic operator

If X is 2, R specifies fix times (the time the object was last updated) for functions and operators named in Y. The time is reported as 7 integer elements (or columns) whose meaning is as follows. The fix time reported for names in Y which are not defined functions or operators is 0.

1 Year
2 Month
3 Day
4 Hour
5 Minute
6 Second
7 Milliseconds (this is always reported as 0)

If X is 3, R specifies execution properties and contains 4 elements (or columns) whose meaning is as follows:

1 Displayable 0 if the object is displayable 1 if the object is not displayable
2 Suspendable 0 if execution will suspend in the object 1 if execution will not suspend in the object
3 Weak Interrupt behaviour 0 if the object responds to interrupt 1 if the object ignores interrupt
4   (always 0)

If X is 4, R specifies object size and contains 2 elements (or columns) which both report the ⎕SIZE of the object.