I have written a csv decoder:
////////////
// CSV reader
proc get_value(s:string, i:&int,res:&string) {
var r = "";
proc add(j:int) { r += s.[j]; }
n := len s;
enum state_t = skip,collect,quote;
fun eq(a:state_t, b:state_t)=> caseno a == caseno b;
var state = skip;
var j:int=n; forall j in *i upto n-1 do
if s.[j] == char "," do break;
elif s.[j] == char " " do
if state == skip do continue;
elif state == quote do add j;
else state = skip;
done;
elif s.[j] == char '"' do
if state == quote do state = skip;
else state = quote;
done;
else add j;
done;
done;
i <- j+1;
res <- r;
}
inp := '1, 2.0 , "Hel lo" , joe';
var res = "";
var pos = 0;
whilst pos < len inp do
get_value (inp, &pos, &res);
if len res >0 do println$ "res=" + res; done;
done;
println "done";
///////////////
Now, first issue to observe is that you cannot compare enums without
writing a comparison routine. [Note the new syntax allowed for enums
too,
but enum s = { ... } still doesn't work, which is what I coded first,
then
had to look up the grammar :]
The second issue is the horrible state/value comparisons.
In the space test, I cannot write a match, because the continue
will not work, since it would be inside a function.
This suggests a procedural match would be useful:
match c with
| 1 => println "x"; println "y";
| 2 => {}
endmatch;
However to parse this compared with
match c with
| 1 => { p; }
endmatch;
is tricky: it requires examining one branch to see if the
return type is void or some other value, and the parser
cannot determine types. It can check for expressions vs
statements however (felix has no expression-as-statement
like C). Still, Dypgen should handle this easily.
--
john skaller
skal...@users.sourceforge.net
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