Date range and match specification syntax

[Ulf Wiger (AL/EAB)]

fun({_,_,D}) when StartDate =< D -> object();
   ({_,_,D}) when D =< EndDate -> object()
end.

(:

/Uffe

-----Original Message-----
From: Torbjorn Tornkvist [mailto:tobbe@REDACTED]
Sent: den 9 oktober 2003 13:28
To: Ulf Wiger (AL/EAB)
Cc: Erlang mailing list
Subject: Re: Date range and match specification syntax


Nice, but how do I express 'or', as in:

1 > ets:fun2ms(fun({_,_,D}) when StartDate =< D; D =< EndDate -> 
object() end).
Error: fun with semicolon (;) in guard cannot be translated into match_spec
{error,transform_error}

? /Tobbe

Ulf Wiger (AL/EAB) wrote:

>On October 7, 2003, Massimo Cesaro wrote:
>  
>
>>>Try to use Query = ets:fun2ms(fun(X) -> ... end) instead,
>>>slightly simpler to use :-) 
>>>      
>>>
>>You kidding, don't you ?! :-)
>>Seriously, I'd like to see a short tutorial or more examples about it.
>>    
>>
>
>
>Here's a short tutorial using ets, and trying to mimic your 
>problem (the ms_transform manual is daunting, I agree):
>
>Your match spec would look pretty much like this:
>
>fun({_,_,D}) when StartDate =< D, D =< EndDate ->
>   object()
>end
>
>
>1> ets:new(cdr,[set,public,named_table,{keypos,2}]).
>cdr
>2> [ets:insert(cdr,{cdr,D,{2003,12,D}}) || D <- lists:seq(1,31)].
>[true,
> true|...]
>3> ets:tab2list(cdr).
>[{cdr,28,{2003,12,28}},
> {cdr,27,{2003,12,27}},
> {cdr,1,{2003,12,1}},
> {cdr,14,{2003,12|...}},
> {cdr,5,{2003|...}},
> {cdr,16,{...}},
> {cdr,7|...},
> {cdr|...},
> {...}|...]
>4> StartDate = {2003,12,3}.
>{2003,12,3}
>5> EndDate = {2003,12,17}.
>{2003,12,17}
>6> P = ets:fun2ms(fun({_,_,D}) when StartDate =< D, D =< EndDate -> object() end).
>[{{'_','_','$1'},
>  [{'=<',{const,{2003,12,3}},'$1'},{'=<','$1',{const,{2003,12,17}}}],
>  ['$_']}]
>7> catch ets:select(cdr,P).
>[{cdr,10,{2003,12,10}},
> {cdr,13,{2003,12,13}},
> {cdr,15,{2003,12,15}},
> {cdr,11,{2003,12,11}},
> {cdr,3,{2003,12,3}},
> {cdr,8,{2003,12,8}},
> {cdr,12,{2003,12,12}},
> {cdr,4,{2003,12,4}},
> {cdr,14,{2003,12,14}},
> {cdr,5,{2003,12,5}},
> {cdr,16,{2003,12,16}},
> {cdr,7,{2003,12,7}},
> {cdr,6,{2003,12,6}},
> {cdr,9,{2003,12,9}},
> {cdr,17,{2003,12,17}}]
>8>  
>  
>