Function to Extract integer from string

Hello Everyone,

I have numerous xml documents that have content that refers to US code of
Federal Regulations (CFRs) e.g.

'GENERAL ['21.197]' or 'PERMIT ['21.197 & '21.199]'

Is there a simple string function that extracts integers from a string?

I am trying to use a series of functions to do the same. e.g.

<xsl:for-each-group select="//Title" group-by=".">
	<xsl:if test="contains(., ''')">
		<xsl:variable name="before"
select="substring-after(.,'[')"/>
		<xsl:variable name="after"
select="substring-before($before,']')"/>
		<xsl:variable name="removespace" select="tokenize($after,
'&amp;')"/>
		<xsl:value-of select="$removespace"/>
		p/>
	</xsl:if>
</xsl:for-each-group>

Which produces:

'21.197
'21.197 '21.199

Desired result:

21.197
21.197
21.199

I will eventually group and sort by number.

Any ideas?

Thanks

Phil