# Function Reference

## `num(value:string, numbase:number = 10):number`

Converts a string to a number in respect of the input base.

Example:
```xn
# Add 1 to all LcId
$("//Name[@LcId]")
{
    attr("LcId", str(num(attr("LcId")) + 1));
};
```

## `str(value:number, numbase:number = 10):string`

Converts a number to a string in any base.

Example:
```xn
# Set ProfileNo to "#o377"
$("//ProfileNo")
{
    text("#o"..str(2**8-1, 8));
};

```

## `hexlit(value:number):string`

Produces a hex literal from an integer with lowercase digits.

Example:
```xn
# Set all module Crc32 to #x00c0ffee
$("//Module[@Crc32]")
{
    attr("Crc32", hexlit(0xC0FFEE));
};
```


## `parselit(literal:string, base:number = 16):string`

Parses a literal number to an integer.

Example:
```xn
# Increase all RevisionNo by 1
$("//Device/Type[@RevisionNo]")
{
    attr("RevisionNo", hexlit(parselit(attr("RevisionNo")) + 1));
};
```

## `lower(text:string):string`

Converts a string to all lower case text.

Example:
```xn
# Convert all device names to lower case
$("//Device/Type")
{
    $("Name") { cdata(lower(cdata())); };
}
```

## `upper(text:string):string`

Converts a string to all upper case text.

Example:
```xn
# Convert all Name tag text in Index nodes from RxPdo to upper case.
$("//RxPdo/Index/Name")
{
    $("Name") { text(upper(text())); };
}
```

## `crc32(poly:number = 0x04C11DB7, init:number = 0, xorOut:number = 0, reflected:bool = false):number`

Calculates the CRC32 checksum from the rendered document starting after the tag close of the context
node up to and including the closing tag.

Example:

For this example `[IND]` is whitespace for indent,
`[CR]` for carriage return and `[LF]` for line feed.

Rendered document:
```xml
<root>[CR][LF]
[IND]<node attribute="yes">[CR][LF]
[IND][IND]<child/>
[IND][IND]Text
[IND]</node>
</root>

XN
```xn
# Calculate CRC of node and store in "crc" attribute as uppercase hexlit
$("//Node") { attr("crc", upper(hexlit(crc32())); }
```

Digested fragment:
```txt
[CR][LF]
[IND][IND]<child/>
[IND][IND]Text
[IND]</node>
```

## `text():string` / `text(value:string):string`

Get or set the text of the context node.

Example:
```xn
# Prefix all Name tag text in Index nodes from TxPdo with "Fault".
$("//TxPdo/Index/Name")
{
    $("Name") { text("Fault" .. text()); };
}
```

## `cdata():string` / `cdata(value:string):string`

Get or set the CDATA of the context node.

Example:
```xn
# For Device with this ProductCode and Revision, modify its CDATA text
$("//Device/Type[@ProductCode='#x0B583052' and @RevisionNo='#x00110000']/..")
{
    $("Name[@LcId='1033']") { cdata("LE2904, 4 Ch. Danger Output 24V, 0.5A, TwinUNSAFE"); };
}
```

## `attr(name:string):string` / `attr(name:string, value:string):string`

Get or set an attribute of the context node by name.

Example:
```xn
# For Device with this ProductCode and Revision, set the revision to #xc0deaffe
$("//Device/Type[@ProductCode='#x0B583052' and @RevisionNo='#x00110000']")
{
    attr("RevisionNo", hexlit(0xC0DEAFFE));
}
```

## `swap(xpath_a:string, xpath_b:string):string = ""`

Swaps two nodes by XPath in the current cotext node.

Example:
```xn
# Swap first and second Entry in RxPdo of Index 0x1600
$("//RxPdo/Index[.='#x1600']/..") { swap("Entry[1]", "Entry[2]"); };

```

## `remove():string = ""`

Removes the context node from the document.

Example:
```xn
# Remove all modules
$("//Module") { remove(); };
```

## `rename(name:string):string = ""`

Renames the context node.

Example:
```xn
# Rename all Device nodes to DeviceX
$("//Device") { rename("DeviceX"); };
```

## `rename(xpath:string, name:string):string = ""`

Renames any nodes matching the XPath in the context node.

Example:
```xn
# Rename all Device nodes Name tags to Label
$("//Device") { rename("Name", "Label"); };
```

## `require(message:string):string = ""`

If the context node is not present, emit an error message.

Example:
```xn
# Emit an error if no Module tags are in the document
$("//Module") { require("No Module definitions!"); };
```