# Combining pattern structure

- This does not describe current behaviour - this is upcoming in version 1.0.0.**

```
d1 $ sound "bd sn"
```

In 'old' Tidal, when combining two patterns, "structure always comes from the left". In the new tidal, you can choose where the structure comes from.

For example:

```
"2 3" + "4 5 6"
```

These two patterns line up like this:

``` | 2 | 3 | | 4 | 5 | 6 | ```

Now by default, the structure comes from _both sides_, so you end up with _four_ events. I've shown the four events below:

```

| 2 | 3 |

+ | 4 | 5 | 6 | = | 6 |7|8| 9 | ```

You can see that the event with the value of `4` fits in the event with value of `2`, so you get a new event equalling their sum `6`. You can see that the onset and duration is the interection, which in this case is just the onset and duration of the original event with the value `4`.

Also see that the event with value `5` is cut in half, to create two, shorter events. Half matches with the `2` event and the other half matches with the `3` event. Again, the onset and duration of both events comes from the intersections.

The fourth and final event comes from the intersection of `3` and `6`, giving a value of `9`.

- Structure from the left

The old behaviour was to take the structure from the left. You can still do this, but in this case using `|+`.

For example:

``` "2 3" |+ "4 5 6" ```

In the above example, you end up with structure from the first, leftmost pattern, like this:

```

| 2 | 3 |

|+ | 4 | 5 | 6 |

= | 6 | 8 |

```

You can see the structure comes from the `2` and `3`. `2` lines up with `4`, and the start of `3` is in `5`, so you end up with `2+4=6` and `3+5=8`.

- Structure from the right

Likewise, you can take the structure from the right, with `+|`. So `"2 3" +| "4 5 6"` looks like:

```

| 2 | 3 |

+| | 4 | 5 | 6 |

= | 6 | 7 | 9 |

```

- All the operators

Note that `+` is actually an alias for `|+|`. So `|+` is to take the structure from the left, `+|` from the right, and `|+|` or `+` for both. Here are all the basic operators you can use to combine structure:

Function Both Left Right

--------- ----- ------

Add `|+|`/`+` `|+` `+|` Multiply `|*|`/`*` `|*` `*|` Subtract `|-|`/`-` `|-` `-|` Divide `|/|`/`/` `|/` `/|` Modulo `|%|` `|%` `%|` Left values `|<|` `|<` `<|` Right values `|>|`/`#` `|>` `>|`

The last two are interesting, they let you only take values from one side. So for example you could take structure from the left, but values from the right with `|>`, for example:

```

| 2 | 3 |

|> | 4 | 5 | 6 |

= | 2 | 9 |

```

This is actually how `#` works in the current tidal.