根據「Tuple」中的第二個元素進行過濾

Question

我試圖用列表中每個元組的總和壓縮此列表，然後對其進行過濾，以便只有列表中總和大於0的元組才被列入。在這一點上，使用下面給出的測試代碼，在「----打印0以上的隨機元組」之後沒有任何內容會打印出來。我錯過了什麼？

sub filter_random_4_toops_by_sum { 
my ($toops, $thresh) = @_; 
my @toops1 =(); 
@toops1 = $toops; 
my @sorted_toops =(); 
my @sortedReturn =(); 
my @filtered_toops =(); 
@sorted_toops = map{[$_, sum(@$_)]} @toops1; 
@filtered_toops = grep {$_[1]> $thresh} @sorted_toops; 
@sortedReturn = map{$_->[0]} @filtered_toops; 
return \@sortedReturn; 
} 

測試代碼：

sub test_step_4 { 
my($sn)= 1; 
my $toops = gen_random_4_toops(1, 100, 5); 
print "---- random 4-toops:\n"; 
foreach(@{$toops}) { 
print "toop $sn:\t(@{$_});\n and sum = " . sum(@{$_}) . "\n"; 
$sn++; 
} 
my $thresh = 55; 
print "\n---- random 4-toops filtered by sum above $thresh:\n"; 
my $filtered_toops = filter_random_4_toops_by_sum($toops, $thresh); 
$sn = 1; 
foreach(@{$filtered_toops}) { 
print "toop $sn:\t(@{$_}); sum = ". sum(@{$_}) . "\n"; 
$sn++; 
} 
} 

測試代碼應該輸出：

---- random 4-toops: 
toop 1: (49 49 4 64); sum = 166 
toop 2: (-2 16 57 76); sum = 147 
toop 3: (-94 93 -48 85); sum = 36 
toop 4: (19 -47 14 38); sum = 24 
toop 5: (-57 80 -60 -35); sum = -72 
---- random 4-toops filtered by sum above 0: 
toop 1: (19 -47 14 38); sum = 24 
toop 2: (-94 93 -48 85); sum = 36 
toop 3: (49 49 4 64); sum = 166 
toop 4: (-2 16 57 76); sum = 147 

相當於我嘗試在Python做（工作）：

def filter_random_4_toops_by_sum(toops, thresh): 
    summit = 0 
    s = [] 
    for i in toops: 
     # pdb.set_trace() 
     summit = 0 
     for d in xrange(0,4): 
      summit += i[d] 
     s.append(summit) 
    # pdb.set_trace() 
    together = zip(toops, s) 
    filtertog = [i for i in together if i[1] > 0] 
    toops = [x[0] for x in filtertog] 
    return toops 

Answer 1

@toops1總是有exac tly一個元素。

@toops1 = $toops; 

應該

@toops1 = @$toops; 

但是，爲什麼不使用@$toops直接而不是複製所有的元素？

sub filter_random_4_toops_by_sum { 
    my ($toops, $thresh) = @_; 
    my @sorted_toops = map { [ $_, sum(@$_) ] } @$toops; 
    my @filtered_toops = grep { $_[1] > $thresh } @sorted_toops; 
    my @sortedReturn = map { $_->[0] } @filtered_toops; 
    return \@sortedReturn; 
} 

甚至

sub filter_random_4_toops_by_sum { 
    my ($toops, $thresh) = @_; 
    return [ 
     map { $_->[0] } 
     grep { $_[1] > $thresh } 
      map { [ $_, sum(@$_) ] } 
       @$toops 
    ]; 
} 

甚至

sub filter_random_4_toops_by_sum { 
    my ($toops, $thresh) = @_; 
    return [ grep { sum(@$_) > $thresh } @$toops ]; 
}