# \atopwithdelims

Plain-TeX infix generalized fraction without a fraction bar, but with explicit left and right delimiters.

https://texform.dev/latex/commands/atopwithdelims

## Metadata

| Field | Value |
| --- | --- |
| Topic | [Fractions and roots](https://texform.dev/latex/topics/fractions-roots) |
| Packages | base |
| Allowed mode | math |
| Tags | discouraged |
| Commonality | low |
| Kind | infix |

## Syntax

### base

Argument specification: `m:D m:D`

Plain-TeX infix generalized fraction without a fraction bar, but with explicit left and right delimiters.

## Examples

```latex
a \atopwithdelims ( ) b
```

[Open in Playground](https://play.texform.dev/?input=a+%5Catopwithdelims+%28+%29+b)

## Renderer support

| Package | MathJax | KaTeX | XeTeX |
| --- | --- | --- | --- |
| base | full | none | full |

## Usage frequency

<0.01% of formulas in the measured corpus contain this entry, rank 229 of 263 entries with frequency data.

## In TeXForm

TeXForm parses this entry as infix syntax; the package determines its argument specification.

### Discouraged in base

This is a plain-TeX infix generalized fraction primitive. Brace-delimited \genfrac-style forms are preferred in LaTeX.

```latex
$1 \atopwithdelims $2 $3 $4 -> \genfrac{$2}{$3}{0pt}{}{$1}{$4}
```

\genfrac is the standard LaTeX generalized-fraction command, makes the delimiter and thickness choices explicit, and avoids infix-scope ambiguity.

### [base/atopwithdelims-to-genfrac](https://texform.dev/rules/base/atopwithdelims-to-genfrac)

Rewrite atopwithdelims to an explicit delimited no-rule genfrac form.

Level: authoring. Fidelity: render.

```latex
#1 \atopwithdelims #2 #3 #4
```

→

```latex
\genfrac{#2}{#3}{0pt}{}{#1}{#4}
```

```latex
\sum_{i=1}^{m} a_i \atopwithdelims [ ] \prod_{j=1}^{n} b_j
```

→

```latex
\genfrac{[}{]}{0pt}{}{\sum_{i=1}^{m} a_i}{\prod_{j=1}^{n} b_j}
```

## Equivalent forms

```latex
\genfrac{$2}{$3}{0pt}{}{$1}{$4}
```

exact. 

## See also

- [\\above](https://texform.dev/latex/commands/above)
- [\\abovewithdelims](https://texform.dev/latex/commands/abovewithdelims)
- [\\atop](https://texform.dev/latex/commands/atop)
- [\\brace](https://texform.dev/latex/commands/brace)
- [\\brack](https://texform.dev/latex/commands/brack)
- [\\choose](https://texform.dev/latex/commands/choose)
- [\\over](https://texform.dev/latex/commands/over)
- [\\overwithdelims](https://texform.dev/latex/commands/overwithdelims)

## Test cases

### base

| Input | Case | MathJax | KaTeX | XeTeX |
| --- | --- | --- | --- | --- |
| a \atopwithdelims ( ( b | Positive: baseline | Pass | Fail | Pass |
| a \atopwithdelims a ( b | Negative: neg:D[0] | Fail | Fail | Fail |
| a \atopwithdelims ( a b | Negative: neg:D[1] | Fail | Fail | Fail |