> ## Documentation Index
> Fetch the complete documentation index at: https://docs.arc.cdata.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Logical Formatters

> Formatters for conditional logic, comparisons, and null/empty checks on attribute values in ArcScript.

## allownull()

Returns *NULL* if the attribute does not exist or the value if it does.

## contains(target\[, ifcontains]\[, ifnotcontains])

Returns *true* if the input string contains the *target*, and *false* otherwise.

You can set the *ifcontains* parameter to an alternate value to return if the input string contains the *target*, and you can set the *ifnotcontains* parameter to an alternate value to return if the input string does not contain the *target*.

### Example

```xml theme={null}
<arc:set attr="myString" value="hello world" />
<arc:if exp="[myString | contains('hello')]">
  <arc:set attr="response" value="hello to you too!" />
  <arc:else>
    <arc:set attr="response" value="I would appreciate a greeting" />
  </arc:else>
</arc:if>
```

## def(ifnotexists\[, ifexists])

Sets the 'default' value of an attribute. If the attribute has not yet been set to a value, set it to the value passed in *ifnotexists*; if the attribute already exists, set it to the value passed in *ifexists*.

### Example

```xml theme={null}
<!-- count the number of loops in an XML document using xmlDOMSearch -->

<arc:set attr="xml.uri" value="[FilePath]" />
<arc:set attr="xml.xpath" value="/Items/test/loop" />

<arc:call op="xmlDOMSearch" in="xml">
  <!-- this code executes for each occurrence of the 'xpath' in the XML document -->
  <arc:set attr="loopCount" value="[loopCount | def(0) | add(1)]" />
</arc:call>
```

## empty(value)

Returns the specified value if the attribute value is empty; otherwise the original attribute value.

* **value**: The value to use if the attribute is empty.

## equals(value\[, ifequal]\[, ifnotequal])

Returns *true* if the input attribute matches the *value*, and *false* otherwise.

If *ifequal* and/or *ifnotequal* are provided, the values in these parameters are returned instead of *true* and *false*.

### Example

```xml theme={null}
<arc:set attr="myItem.code" value="[xpath(data/lineitems/itemcode)]" />
<arc:if exp="[myItem.code | equals('A5')]">
  <arc:set attr="myItem.name" value="spoon" />
  <arc:else>
    <arc:set attr="myItem.name" value="fork" />
  </arc:else>
</arc:if>
```

## ifequal(value\[, ifequals]\[, ifnotequals])

Compares the attribute value with the first parameter value and returns *true* (or *ifequals*) if they are equal and *false* (or *ifnotequals*) if they are not.

* **value**: The string to compare with the attribute value.
* **ifequals**: The optional value returned if the attribute value equals the value represented by the first parameter.
* **ifnotequals**: The optional value returned if the attribute value does not equal the value represented by the first parameter.

## ifmatches(value\[, ifmatch]\[, ifnotmatch])

Returns *true* (or *ifmatch*) if the attribute value matches the first parameter, otherwise *false* (or *ifnotmatch*).

* **value**: The value to compare with the attribute value.
* **ifmatch**: The optional value returned if the attribute value matches the parameter value.
* **ifnotmatch**: The optional value returned if the attribute value does not match the parameter value.

## isalphabetic(\[ifalpha]\[, ifnotalpha])

Returns *true* (or *ifalpha*) if all characters in the attribute value are alphabetic and there is at least one character, and *false* (or *ifnotalpha*) otherwise.

* **ifalpha**: The optional value returned if the attribute value is alphabetic.
* **ifnotalpha**: The optional value returned if the attribute value is not alphabetic.

## isalphanumeric(\[ifalphanum]\[, ifnotalphanum])

Returns *true* (or *ifalphanum*) if all characters in the attribute value are alphanumeric and there is at least one character, and *false* (or *ifnotalphanum*) otherwise.

* **ifalphanum**: The optional value returned if the attribute value contains only alphabetic or numeric characters.
* **ifnotalphanum**: The optional value returned if the attribute value contains nonalphabetic or nonnumeric characters.

## islower(\[iflower]\[, ifnotlower])

Returns *true* (or *iflower*) if all letters in the attribute value are lowercase and there is at least one character that is a letter, and *false* (or *ifnotlower*) otherwise.

* **iflower**: The optional value returned if the attribute value is lowercase.
* **ifnotlower**: The optional value returned if the attribute value is not lowercase.

## isnumeric(\[ifnum]\[, ifnotnum])

Returns *true* (or *ifnum*) if all characters in the attribute value are digits and there is at least one character, and *false* (or *ifnotnum*) otherwise.

* **ifnum**: The optional value returned if the attribute value is numeric.
* **ifnotnum**: The optional value returned if the attribute value is not numeric.

## isspace(\[ifspace]\[, ifnotspace])

Returns *true* (or *ifspace*) if there are only white-space characters in the attribute value and there is at least one character, and *false* (or *ifnotspace*) otherwise.

* **ifspace**: The optional value returned if the attribute value is a space.
* **ifnotspace**: The optional value returned if the attribute value is not a space.

## isupper(\[ifupper]\[, ifnotupper])

Returns *true* (or *ifupper*) if all letters in the attribute value are uppercase and there is at least one character that is a letter, and *false* (or *ifnotupper*) otherwise.

* **ifupper**: The optional value returned if the attribute value is uppercase.
* **ifnotupper**: The optional value returned if the attribute value is not uppercase.

## notequals(value\[, notequals]\[, equals])

Compares the attribute value with the first parameter value. Returns *true* (or *notequals*) if they are not equal, and *false* (or *equals*) if they are.

* **value**: The string to compare with the attribute value.
* **notequals**: The optional value returned if the attribute value does not equal the value represented by the first parameter.
* **equals**: The optional value returned if the attribute value equals the value represented by the first parameter.

## startswith(target\[, iftrue]\[, iffalse])

Returns *true* if the input string starts with the value specified as the *target*, and *false* otherwise.

If *iftrue* is provided, this value is returned instead of *true* when the *target* is found, and if *iffalse* is provided, this value is returned instead of *false* when the *target* is not found.

### Example

```xml theme={null}
<arc:set attr="myString" value="Sir, your carriage is ready." />
<arc:if exp="[myString | startswith('Sir')]">
  <arc:set attr="response" value="Thank you." />
  <arc:else>
    <arc:set attr="response" value="Use your manners." />
  </arc:else>
</arc:if>
```