r3wp [groups: 83 posts: 189283]
  • Home
  • Script library
  • AltME Archive
  • Mailing list
  • Articles Index
  • Site search
 

World: r3wp

[Core] Discuss core issues

Pekr
26-Jun-2006
[4935x2]
I would prefer 29-Feb-2006 error, as well as e.g. error? try [load 
380.250.250] being a bit more relaxed in interpreter ...
how can I catch such syntax errors?
Graham
26-Jun-2006
[4937]
what is your problem?
Ladislav
26-Jun-2006
[4938]
error? try [load "29-Feb-2006"] ; == true
Pekr
26-Jun-2006
[4939x4]
the problems is uncatchable error
I am not talking about string ....
I am not sure I can meet with such situation in real-life :-) I just 
got asked by Bobik. The thing was, that in sqlite date field there 
can be invalid date. Now I am not sure how is the conversion done, 
if via string, but if you simply type such invalid date in console, 
it can't be recovered, and that is my objection in general ...
shouldn't we be always able to recover from whatever error happens?
DideC
26-Jun-2006
[4943]
To be executed, a script is loaded in a whole. So each values is 
loaded/binded and your error appears at this time, not while the 
expression is evaluated.
Pekr
26-Jun-2006
[4944]
do you mean that I can catch the error during load? but why loading 
value itself fails?
Graham
26-Jun-2006
[4945]
what uncatchable error?
Pekr
26-Jun-2006
[4946x2]
try to type in console 29-feb-2006 ....
although it is invalid, I thought that by error? try [29-Feb-2006] 
I will be able to recover eventually, which is not the case ...
Graham
26-Jun-2006
[4948x4]
>> if error? try [ load form 29-feb-2006 ][print "date format error" 
]
** Syntax Error: Invalid date -- 29-feb-2006

** Near: (line 1) if error? try [ load form 29-feb-2006 ][print "date 
format error" ]
>>
>> if error? try [ load "29-feb-2006" ][print "date format error" 
]
date format error
>>
Doesn't like the 29-Feb-2006 as a date string
date type!
Henrik
26-Jun-2006
[4952]
looks like a bug?
Graham
26-Jun-2006
[4953]
Looks like it.
Volker
26-Jun-2006
[4954x2]
Does not like 32-may-2006 too. Isn't this more a feature than a bug?
error? try [29-Feb-2006]

 is "word! word! [what-is-this?]". Reol has no idea what to do with 
 "error?" at that time.
Pekr
26-Jun-2006
[4956x2]
well, but Volker, anyway, we got to state, where we have non-recoverable 
interpreter state, don't we?
I know the date is invalid, but .... the same goes for tupple, e.g. 
380.250.250
Volker
26-Jun-2006
[4958x2]
>> 380.250.250
** Syntax Error: Invalid tuple -- 380.250.250
** Near: (line 1) 380.250.250
you are not at interpreter state at that time. think of 'load finding 
an error at compile-time.
Pekr
26-Jun-2006
[4960]
I know, I just don't like the fact, console is not safe from such 
errors ..
Volker
26-Jun-2006
[4961x2]
Thats why ladislav puts the date in a string. compiled later.
how should it work instead?
Pekr
26-Jun-2006
[4963x3]
ok, can we meet with state, where your app returns directly such 
invalid date? e.g. mentioned link to sqlite date field?
how would it work? dunno? a bit more relaxed evaluation? interpreter 
finding string 29-Feb-2006 - it is valid format, not just valid value. 
Under some condition it could be even valid date (leap year). I would 
expect even such error to be catchable ...
ok, so I will have to trust gurus the fact, that technically it can't 
be fixed :-)
Henrik
26-Jun-2006
[4966]
how does Rebol not know how to handle 29-feb-2006 as a date! ? I'm 
not sure I understand this, because how then is the unrecoverable 
error generated? from what I see, you'll always need to wrap some 
precautionary measures around handling dates to avoid this. that's 
not good design.
Volker
26-Jun-2006
[4967]
internal its not a string, but a number. you would get 29-feb-2006 
as 1-mar-2006. would that be ok?
Pekr
26-Jun-2006
[4968]
anyway ... I don't like current state, that is all. I even don't 
know consequences, just a feeling :-) Maybe Carl could give us his 
opinion, if it is bug or not, and if not, if this is desirable behavior 
...
Volker
26-Jun-2006
[4969]
maybe a hook in 'load, whcih can do some spellchecking?
Pekr
26-Jun-2006
[4970]
hmm, help me to imagine, how does interpreter internally works? So 
let's simplify it - it reaches 280.250.250 tuple. It tries to parse 
it. It eventually recognises it as a tupple, otherwise it would not 
return "Invalid tuple", no? But then it finds invalid values ... 
why just doesn't it recognise, it is part of 'try block and does 
not throw error, which would be catchable?
Volker
26-Jun-2006
[4971x4]
because  it does not try to parse it. it has already.
'load does the parsing. after load has finished, all datatypes are 
in an optimized form.
if load cant handle something, it is helpless. it does not know something 
is inside a try-block. it only knows it has loaded a lot of words 
already and the followingtext is not right.
that means the error happens when the sourcecode with the try is 
laoded, before try as any achance to be executed.
Pekr
26-Jun-2006
[4975]
then maybe there could be two phases of load .... parse form, not 
the value first :-) 999.999.999 for a valid tuple! datatype. It is 
too strict, in opposite to:

>> email? to-email "nonsense"
== true
Henrik
26-Jun-2006
[4976]
that's why we have the term "loadable", right? Carl talks about this 
when parsing. Otherwise this wouldn't be a problem.
Volker
26-Jun-2006
[4977x3]
maybe some datatype "weird" with the original string and a type-suggestion? 
but then you get problems with ambiguities.
what is a typo, what ignored? 6-pfu-206 ?
maybe i amn to conservative, used to compilers which tell me each 
bug, instead of fixin it. always fearing a misunderstanding when 
the compiler would try toguess itself. if it could reliable guess, 
thatwould be cool :)
Henrik
26-Jun-2006
[4980]
as long as there are no dead ends with truly unrecoverable errors...
Pekr
26-Jun-2006
[4981x2]
Volker - but how does it know of 29-Feb-2006? Under some condition, 
it is valid date ... imo already higher level logic is applied here, 
no?
- btw - from my pov, regard this discussion academic .... I don't 
understand compilers, interpreters, just speculating here :-)
Graham
26-Jun-2006
[4983x2]
quick question ... I have a number of simple objects that I create 
on the web server and then send back to client in molded format.
how does one restore them back to objects?