# `Expresso.Element.MathLine`
[🔗](https://github.com/rellen/expresso/blob/main/lib/expresso/element/math_line.ex#L1)

A line of a derivation in a `math` element

The `line` entity takes the relation of the line as its first argument, such
as `"="` or `~S"\to_\beta"`, in LaTeX. The `tex` option gives the term of
the line in LaTeX, and the `why` option gives the reason as plain text.
`Expresso.Element.Math.check/1` writes the lines into one formula of the
environment `aligned`, so the lines align on their relations, and each line
becomes a part with the name `line1`, `line2` and so on, or with its `name`.

The `steps` option takes 1 or 2. With 2, the links of the line move at its
first step, and the other symbols of the line show at the next step.

A line from a `rewrite` entity has a step for each group of its phases, the
reason in LaTeX in `why_tex` when the rewrite gives no `why`, and in
`rewrite` the colors of its parts and the steps when its copies move.
`Expresso.Element.Math.Rewrite.expand/1` writes them.

# `t`

```elixir
@type t() :: %Expresso.Element.MathLine{
  __spark_metadata__: term(),
  name: term(),
  relation: term(),
  rewrite: term(),
  steps: term(),
  tex: term(),
  why: term(),
  why_tex: term()
}
```

The struct of a line of a derivation

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*Consult [api-reference.md](api-reference.md) for complete listing*