Szathmáry László honlapja @ DEIK

Slicing in D is very similar to Python. However, they are not completely identical.

Similarities

(1) similarities
def main(): numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] s = "0123456789" print(numbers[0:2]) # [0, 1] print(s[0:2]) # 01 print(numbers[7:]) # [7, 8, 9] print(s[7:]) # 789 print(numbers[-2:]) # [8, 9] print(s[-2:]) # 89	import std.stdio; void main() { int[] numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]; string s = "0123456789"; writeln(numbers[0 .. 2]); // [0, 1] writeln(s[0 .. 2]); // 01 writeln(numbers[7 .. $]); // [7, 8, 9] writeln(s[7 .. $]); // 789 writeln(numbers[$ - 2 .. $]); // [8, 9] writeln(s[$ - 2 .. $]); // 89 }

Differences

(2) differences
def main(): numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] s = "0123456789" print(numbers[2:0]) # [] print(s[2:0]) # "" (empty string) print(numbers[8:100]) # [8, 9] print(s[8:100]) # "89"	import std.stdio; void main() { int[] numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]; string s = "0123456789"; // if start index > end index => error // writeln(numbers[2 .. 0]); // error // writeln(s[2 .. 0]); // error // if end index > length => error // writeln(numbers[8 .. 100]); // error // writeln(s[8 .. 100]); // error }

Solution

We can have a Python-like behaviour with the introduction of a safety function.

(3) solution

def main():
numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
s = "0123456789"

print(numbers[2:0]) # []
print(s[2:0]) # "" (empty string)

print(numbers[8:100]) # [8, 9]
print(s[8:100]) # "89"

# normal call
print(numbers[2:5]) # [2, 3, 4]
print(s[2:5]) # "234"

import std.stdio;

T[] safeSlice(T)(T[] arr, size_t start, size_t end)
{
if (start >= arr.length || start > end)
return []; // empty slice
// else:
return (end <= arr.length) ? arr[start .. end] : arr[start .. $];
}

void main()
{
int[] numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
string s = "0123456789";

writeln(safeSlice(numbers, 2, 0)); // []
writeln(safeSlice(s, 2, 0)); // "" (empty string)

writeln(safeSlice(numbers, 8, 100)); // [8, 9]
writeln(safeSlice(s, 8, 100)); // "89"

// normal call
writeln(safeSlice(numbers, 2, 5)); // [2, 3, 4]
writeln(safeSlice(s, 2, 5)); // "234"
}