Pointer arithmetic in Mojo

Adding to a pointer moves it by whole elements, never by bytes.

from std.memory import alloc


def main():
    var block = alloc[Int](6)
    for i in range(6):
        block[i] = i * 10
    var tail = block + 3
    print(tail[0], tail[1], tail[2])
    var back = tail - 2
    print(back[0])
    block.free()

How it works

1. The block is filled through plain index assignment.
2. block + 3 points at the fourth element and indexes on from there.
3. Subtracting steps back, and only the original pointer is freed.

Keywords and builtins used here

• Int
• def
• for
• main
• print
• range
• var

The run, in numbers

Lines

12

Characters to type

207

Tokens

69

Three-star pace

65 tpm

At the three-star pace of 65 tokens a minute, this run takes about 64 seconds.

Type this snippet

Step 2 of 4 in Memory, step 18 of 22 in Parameters & SIMD.

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Pointer arithmetic in other languages

• C