On Monday, 7 September 2015 at 10:25:09 UTC, deed wrote:
Right, it's like
int x = 3;
// x + 5; // Just an expression evaluated to 8,
// but what do you want to do with it?
// It won't affect your program and the
// compiler will give you an error.
int y = x + 5; // But you can assign the expression to
// a new variable
x = x + 5; // or you can assign it back
writeln(x); // or you can pass it to a function.
// For your case:
int[] arr = [1, 2, 3, 2, 1, 4];
arr.sort; // Operating on arr in place -> arr itself
is mutated
arr.writeln; // [1, 1, 2, 2, 3, 4]
arr.uniq; // Not operating on arr, it's like the
expression
// x + 5 (but no compiler error is given).
arr.uniq.writeln; // [1, 2, 3, 4] (Expression passed to
writeln)
arr.writeln; // [1, 1, 2, 2, 3, 4] (Not affected)
int[] newArr = arr.uniq.array;
// Expression put into a new array assigned
to newArr
newArr.writeln; // [1, 2, 3, 4]
arr.writeln; // Still the sorted array. [1, 1, 2, 2, 3, 4]
arr = arr.uniq.array; // Now arr is assigned the uniq array
arr.writeln; // [1, 2, 3, 4]
You need to know whether the function will mutate your array;
sort does, while uniq doesn't. If you want to do things
requiring mutation, but still want your original data
unchanged, you can duplicate the data with .dup before the
mutating operations, like this:
int[] data = [1, 2, 2, 1];
int[] uniqData = data.dup.sort.uniq.array;
data.writeln; // [1, 2, 2, 1] Unchanged, a duplicate was
sorted.
uniqData.writeln; // [1, 2]
As an aside, you should use `sort()` instead of the
parentheses-less `sort`. The reason for this is that doing
`arr.sort` invokes the old builtin array sorting which is
terribly slow, whereas `import std.algorithm; arr.sort()` uses
the much better sorting algorithm defined in Phobos.
