Spurious value error in J6.01 betas:
4 : 'x =. x , y'
4 : 'x =. x , y'
|value error: y
| 4 :'x =. x , y'
A simpler example is just 3 :'y=.y,y' . Note that even though the error is
thrown, the verb is still returned.
I was writing a verb that accumulates data in a global buffer (because it's
called asynchronously). If I don't define (assign to) the buffer before I
define the verb in the script, I get the spurious error:
_1 -: nc {.;:'BUFFER' NB. BUFFER is undefined
1
async =: 3 : 'BUFFER =: BUFFER , y'
|value error: y
| async=: 3 :'BUFFER =: BUFFER , y'
async NB. Verb was still assigned
3 : 'BUFFER =: BUFFER , y'
I think this is related to the new append-in-place smarts, because other forms
don't trigger the bug:
v0 =: 3 : 'y'
v1 =: 3 : 'BUFFER , y'
v2 =: 3 : 'BUFFER =: y'
v3 =: 3 : 'BUFFER =: BUFFER , y'
|value error: y
| v3=: 3 :'BUFFER =: BUFFER , y'
v4 =: 3 : 'BUFFER =: y , BUFFER'
v5 =: 3 : 'BUFFER =: BUFFER , BUFFER'
|value error: BUFFER
| v5=: 3 :'BUFFER =: BUFFER , BUFFER'
v5 =: 3 : 'BUFFER =: BUFFER , 0'
Note (from second transcript) that even if the spurious error is thrown, the
verb still gets defined. If this verb is invoked, another surprise occurs:
async 'hello'
|domain error: async
| BUFFER=:BUFFER ,y
Why is this a domain error? I expect a value error.
BUFFER is an undefined name, so it should be treated as a verb. If BUFFER
were really a verb, it would be invoked monadically with the argument ,y
(the ravel of y ), the result of which would then be assigned to BUFFER ,
changing its nameclass to noun. But, since BUFFER is not defined, I expect
that monadic invocation to fail with a value error.
I would expect a domain error if I invoked v4 'hello' because of J6's new NVV
train (meaning v4 would try to return a verb), but that's not the case in
async .
Is this a bug? I hesitate to assert so because whenever I report a "misspelled
error" I'm told it's not a bug. But consider:
_1=nc ;:'BUFFER OTHER' NB. Both undefined
1 1
3 : 'BUFFER , 22' 0
|value error: BUFFER
| BUFFER,22
3 : 'OTHER =: BUFFER , 22' 0
|value error: BUFFER
| OTHER=: BUFFER,22
3 : 'BUFFER =: OTHER , 22' 0
|value error: OTHER
| BUFFER=: OTHER,22
3 : 'BUFFER =: BUFFER , 22' 0
|domain error
| BUFFER=:BUFFER ,22
If it's not a bug, I would appreciate an explicit explanation of the reason.
-Dan
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