# physics/abs-to-vert-fence

Rewrite abs to explicit vertical bar fences.

https://texform.dev/rules/physics/abs-to-vert-fence

## Metadata

| Field | Value |
| --- | --- |
| Key | physics/abs-to-vert-fence |
| Level | faithful |
| Fidelity | render |
| Enabled by packages | physics |
| Profiles | Faithful, Corpus, Equiv |

## Rewrite patterns

### auto-sized

From:

```latex
\abs{#1}
```

To:

```latex
\left| #1 \right|
```

### fixed-size

From:

```latex
\abs*{#1}
```

To:

```latex
| #1 |
```

## Examples

Examples show the rule in isolation, not a complete normalization profile.

### abs inequality

Before:

```latex
\abs{x-y}<\varepsilon
```

After this rule:

```latex
\left| x-y \right|<\varepsilon
```

Packages: base, physics.

Rendering verified with the declared packages.

### abs fraction body

Before:

```latex
\abs{\frac{x}{y}}=1
```

After this rule:

```latex
\left| \frac{x}{y} \right|=1
```

Packages: base, physics.

Rendering verified with the declared packages.

### abs star fixed size

Before:

```latex
\abs*{x-y}<\varepsilon
```

After this rule:

```latex
| x-y |<\varepsilon
```

Packages: base, physics.

Rendering verified with the declared packages.

## Triggers

- [\\abs](https://texform.dev/latex/commands/abs)

## Eliminates

- [\\abs](https://texform.dev/latex/commands/abs)

## Produces

- [\\left](https://texform.dev/latex/commands/left)
- [\\right](https://texform.dev/latex/commands/right)

## Upstream

- [physics/absolutevalue-to-abs](https://texform.dev/rules/physics/absolutevalue-to-abs): Collapse absolutevalue to the shorter abs helper before fence expansion.

## Same family

- [base/Big-class-variants-to-Big](https://texform.dev/rules/base/Big-class-variants-to-Big): Collapse \Bigl, \Bigr, \Bigm to \Big.
- [base/Bigg-class-variants-to-Bigg](https://texform.dev/rules/base/Bigg-class-variants-to-Bigg): Collapse \Biggl, \Biggr, \Biggm to \Bigg.
- [base/big-class-variants-to-big](https://texform.dev/rules/base/big-class-variants-to-big): Collapse \bigl, \bigr, \bigm to \big.
- [base/bigg-class-variants-to-bigg](https://texform.dev/rules/base/bigg-class-variants-to-bigg): Collapse \biggl, \biggr, \biggm to \bigg.
- [base/Big-delimiter-size-drop](https://texform.dev/rules/base/Big-delimiter-size-drop): Drop the fixed delimiter size imposed by \Big.
- [base/Bigg-delimiter-size-drop](https://texform.dev/rules/base/Bigg-delimiter-size-drop): Drop the fixed delimiter size imposed by \Bigg.
- [base/big-delimiter-size-drop](https://texform.dev/rules/base/big-delimiter-size-drop): Drop the fixed delimiter size imposed by \big.
- [base/bigg-delimiter-size-drop](https://texform.dev/rules/base/bigg-delimiter-size-drop): Drop the fixed delimiter size imposed by \bigg.
- [physics/absolutevalue-to-abs](https://texform.dev/rules/physics/absolutevalue-to-abs): Collapse absolutevalue to the shorter abs helper before fence expansion.
- [physics/evaluated-to-eval](https://texform.dev/rules/physics/evaluated-to-eval): Collapse evaluated to the shorter eval helper before eval expansion.
- [physics/quantity-to-qty](https://texform.dev/rules/physics/quantity-to-qty): Collapse quantity to the shorter qty helper.
- [physics/Bqty-to-brace-fence](https://texform.dev/rules/physics/Bqty-to-brace-fence): Rewrite Bqty to explicit brace fences.
- [physics/bqty-to-bracket-fence](https://texform.dev/rules/physics/bqty-to-bracket-fence): Rewrite bqty to explicit bracket fences.
- [physics/norm-to-double-vert-fence](https://texform.dev/rules/physics/norm-to-double-vert-fence): Rewrite norm to explicit double-vertical-bar fences.
- [physics/pqty-to-paren-fence](https://texform.dev/rules/physics/pqty-to-paren-fence): Rewrite pqty to explicit parenthesis fences.
- [physics/eval-expand](https://texform.dev/rules/physics/eval-expand): Expand eval notation to the explicit fence-and-bar form.

## Notes

The star branch is the fixed-size form emitted by physics Quantity for braced arguments.

## Disable this rule

```python
TransformEngine(profile="corpus", disable_rules=["physics/abs-to-vert-fence"])
```

```javascript
new TransformEngine({ profile: 'corpus', disableRules: ['physics/abs-to-vert-fence'] })
```

[Open in Playground](https://play.texform.dev/?input=%5Cabs%7Bx-y%7D%3C%5Cvarepsilon)