A little piece of code which uses two closures, partial application and a higher order function.
The poor perl code reflects my few weeks on this language.
# getRowsLazy :: DB_Handle -> (String -> String -> ()) -> (SQLQuery ->
+ {':parm1' => value, ...} -> [[DBType, ..., DBType]])
# Closure on $dbh, lazy version and partial application on the first t
+wo params
#
# ex: my $dbh = ...DBI connect...
my $getRows = F::getRowsLazy($dbh, sub { myErrFun($[0], $[1], $M
+Y_FUN_NAME, $MY_TRACE_LEVEL) } );
# ...
# my $iter = $getRows->("select * from device_param where ID=:id",
+ {':id' => 123456});
# while (my $row = $iter->()) {
# print $row->[0] . ", " . $row->[1] . "\n";
# }
#
sub F::getRowsLazy {
my ($dbh, $errFun);
return sub {
my ($sql,$p) = @_;
my $sth = $dbh->prepare($sql) || $errFun->("Error in DBI::prepare"
+, $dbh->errstr() );
while (my ($k,$v) = each(%$p)) {$sth->bind_param($k, $v);}
$sth->execute() || $errFun->("Error in DBI::execute", $dbh->errstr
+() );
my $yield = sub {
my $row = $sth->fetchrow_arrayref;
if ($row) {return $row;}
$sth->finish();
return undef;
};
return $yield; # the call to $yield->() returns a referenc
+e; doesn't work with array, but I don't know way
}
};