#### 16.4.1.2 Integer Sequence Operator ‘`:`’ ¶

The syntax `first:last:step` yields a row vector of consecutive integers from first to last counting by step. The final `:step` is optional and defaults to 1 when omitted.

Each of first, last, and step must be a scalar and should be an integer (any fractional part is discarded). Because ‘`:`’ has a high precedence, operands other than numeric literals must usually be parenthesized.

When step is positive (or omitted) and end < start, or if step is negative and end > start, then the result is an empty matrix. If step is 0, then PSPP reports an error.

Here are some examples:

`1:6` | ⇒ | `{1, 2, 3, 4, 5, 6}`
`1:6:2` | ⇒ | `{1, 3, 5}`
`-1:-5:-1` | ⇒ | `{-1, -2, -3, -4, -5}`
`-1:-5` | ⇒ | `{}`
`2:1:0` | ⇒ | (error)