---
title: "Postfix"
language: "en"
type: "Symbol"
summary: "Postfix[f[expr]] prints with f[expr] given in default postfix form: expr // f. Postfix[f[expr], h] prints as exprh."
keywords: 
- postfix notation
- reverse polish notation
- rpn
canonical_url: "https://reference.wolfram.com/language/ref/Postfix.html"
source: "Wolfram Language Documentation"
related_guides: 
  - 
    title: "Symbolic Notational Forms"
    link: "https://reference.wolfram.com/language/guide/SymbolicNotationalForms.en.md"
  - 
    title: "Wolfram Language Syntax"
    link: "https://reference.wolfram.com/language/guide/Syntax.en.md"
related_functions: 
  - 
    title: "Infix"
    link: "https://reference.wolfram.com/language/ref/Infix.en.md"
  - 
    title: "Prefix"
    link: "https://reference.wolfram.com/language/ref/Prefix.en.md"
  - 
    title: "PrecedenceForm"
    link: "https://reference.wolfram.com/language/ref/PrecedenceForm.en.md"
related_tutorials: 
  - 
    title: "Defining Output Formats"
    link: "https://reference.wolfram.com/language/tutorial/TextualInputAndOutput.en.md#9464"
  - 
    title: "Operator Input Forms"
    link: "https://reference.wolfram.com/language/tutorial/OperatorInputForms.en.md"
---
# Postfix

Postfix[f[expr]] prints with f[expr] given in default postfix form: expr//f. 

Postfix[f[expr], h] prints as exprh.

## Details

* ``Postfix[expr, h, precedence, grouping]`` can be used to specify how the output form should be parenthesized.

* The special input form ``expr//f`` is directly interpreted as ``f[expr]`` and does not involve ``Postfix``. »

---

## Examples (3)

### Basic Examples (2)

Display ``f[x]`` in postfix form:

```wl
In[1]:= Postfix[f[x]]

Out[1]= Postfix[f[x]]
```

---

Use a special character as a postfix operator:

```wl
In[1]:= Postfix[f[x], "§"]

Out[1]= Postfix[f[x], "§"]
```

### Possible Issues (1)

The output from ``Postfix`` contains invisible tagging that preserves its meaning:

```wl
In[1]:= Postfix[f[a]]

Out[1]= Postfix[f[a]]
```

Copying the output and using it in a input cell produces the same result:

```wl
In[2]:= Postfix[f[a]]

Out[2]= Postfix[f[a]]
```

Typing in a visually identical result from scratch will produce a different result:

```wl
In[3]:= a//f

Out[3]= f[a]
```

## See Also

* [`Infix`](https://reference.wolfram.com/language/ref/Infix.en.md)
* [`Prefix`](https://reference.wolfram.com/language/ref/Prefix.en.md)
* [`PrecedenceForm`](https://reference.wolfram.com/language/ref/PrecedenceForm.en.md)

## Tech Notes

* [Defining Output Formats](https://reference.wolfram.com/language/tutorial/TextualInputAndOutput.en.md#9464)
* [Operator Input Forms](https://reference.wolfram.com/language/tutorial/OperatorInputForms.en.md)

## Related Guides

* [Symbolic Notational Forms](https://reference.wolfram.com/language/guide/SymbolicNotationalForms.en.md)
* [Wolfram Language Syntax](https://reference.wolfram.com/language/guide/Syntax.en.md)

## History

* Introduced in 1988 (1.0)