# Flowing#

While deduction arrows indicate the logical structure of a proof, it can be useful to have another type of arrow, to help direct the reader to examine the nodes of the proof in a certain order.

For example, it is good to guide the reader to the introduction of new symbols, before visiting nodes that use those symbols.

For this, Proofscape diagrams offer *flow* arrows, which are drawn dashed
instead of solid.

Example:

```
A, therefore B. C implies D.
```

There are three keywords in the **flow** keyword category:

now |
next |
claim |

and the rule governing the drawing of flow arrows is as follows:

A flow arrow will be drawn from node

`A`

to node`B`

when all the keywords between`A`

and`B`

(if any) are in themodaland/orflowcategories. In particular, a flow arrow will be drawn if there arenokeywords at all between`A`

and`B`

.

Thus,

```
A, therefore B. Let I. Then C, using D.
```

```
Suppose S. Then A. Now let I. Then B, by A and C.
```

Notice that in this last case there are two arrows leaving node `A`

, and the
purpose of the flow arrow is to tell us that we should consider the `intr`

node `I`

first, before considering node `B`

.