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II. Functions XSLT
II.A. List of functions XSLT

II.B. Loops with xsl: for-each
I have lied (oh the villain). In fact, xsl: for-each is not really a loop as a "for" language C. This function will take all the nodes of a request XPATH, and will apply their treatment. Let's already the source file:
<liste>
   <invite> Moi </ invite>
   <invite> Amélie </ invite>
   <invite> Marie </ invite>
   <invite> Jéméry </ invite>
</ list>

Then the XSLT code that will generate a list HTML:

<ul>
 <xsl:for-each>
 <li>
 <xsl:apply-templates select="." />
 </li>
 </for-each>
 </ul>

II.C. Function xsl: if 

The instruction xsl: if possible to run or not certain parts of the code. Example of instruction if: 

<xsl:if test="nom == 'Victor'">
 <xsl:text> Wishes, it looks like my first name! </ xsl: text>
 </xsl:if>

Ok, but where is the xsl: else? Uh ... Sorry, there's no :-( We must use xsl: choose: - / 

II.D. Function xsl: choose 

The function xsl: choose can perform different codes according to different conditions. Example of instruction choose: 

<xsl:choose>
 <xsl:when test="name= 'Victor'">
 <xsl:text> Hi Victor, it boume? </ xsl: text>
 </xsl:when>
 <xsl: when test = "name = 'Pierre' ">
 <xsl:text> chisel Done ... sorry, it was zero. </ xsl: text>
 </xsl:when>
 <xsl: when test = "name = 'Pierre' ">
 <xsl:text> Message impersonal and cold: Hello. </ xsl: text >
 </xsl:when>
 </xsl:choose>
It often uses xsl: choose as an alternative to xsl: if to have xsl: other (which replaces xsl: else that does not exist). 

II.E. A function without parameters (xsl: template and xsl: call-template) 

To declare a function, it uses the xsl: template. Example: 

<xsl:template name="hello_world">
<xsl:text>Hello World !</xsl:text>
</xsl:template>
It will now call our function with xsl: call-template: 
<xsl:call-template name="hello_world" /> 
That's all ... Ben Yeah. In fact, the entire beast! 

II.F. A function with parameters (xsl: param and xsl: with-param) 
<xsl:template name="affiche_somme">
 <xsl:param name="a" select="0" />
 <xsl:param name="b" select="0" />
 <xsl:text>a = </xsl:text>
 <xsl:value-of select="$a" />
 <xsl:text>, b = </xsl:text>
 <xsl:value-of select="$b" />
 <xsl:text>, et a+b = </xsl:text>
 <xsl:value-of select="$a + $b" />
 <xsl:text>.</xsl:text>
 </xsl:template>
 When writing <xsl:param name="a" select="0" />: 0 is the default setting 
a. Call this miracle of programming, always via xsl: call-template: 
 <xsl:call-template name="affiche_somme">
 <xsl:with-param name="a" select="173" />
 <xsl:with-param name="b">9001</xsl:with-param>
 </xsl:call-template>
You know what, the worst is that it works! This produces an output of 
style: 
 a = 173, b = 9001, and a + b = 9174. 

III. Bouts of useful codes
III.A. A real loop
I like to tell you right away: XSLT is not done to make loops! It is a language that uses recursive algorithms, not iterative. It is much cleaner, but less natural.

But sometimes, we still need loops. And yes, they never leave us, we programmer :-) I therefore offers this little piece of code that could perhaps save your life (who knows?):
<xsl:template name="boucle">
<xsl:param name="debut" select="0" />
<xsl:param name="fin" select="0" />
<xsl:text>i = </xsl:text>
<xsl:value-of select="$debut" />
<br/>
<xsl:if test="$debut <$ end">
<xsl:call-template name="boucle">
<xsl:with-param name="debut" select="($debut)+1" />
<xsl:with-param name="fin" select="$fin" />
</xsl:call-template>
</xsl:if>
</xsl:template>

Prototype of a function: loop ($ debut, $ fin). It will display the numbers $ debut to $ end. What to say? Ah yes, "<" bizarre. Well that is still in XML, and "alt" can not be written as it stood. We must write in its encoded form "<". That's all!

IV. Functions XPATH

V. String (XPATH)
V.A. List of functions

V.B. Example (1)
It will say that the current node (.) Contains my email: victor.stinner + haypocalc.com (read '@' and not'+'). Example usage functions concat, substring-after and substring-before:

<xsl:value-of select="concat(
 substring-before(.,'@'),
 'ON',
 substring-after(.,'@'))" /> 
Well, yes, you can write on several lines if you like, hey hey hey! Released: "victor.stinner ON haypocalc.com" cool, that's what I wanted to do (hide my email) ;-)

V.C. Example (2)
Let's say the current node (.) Contains the name of an image: "bibi_phoque.gif." It will replace the extension '. Gif'. Png. Example use functions and substring length:

<xsl:value-of select="concat(substring(.,length(.)-4),'.png')" />

Well, the function xsl: string-before "could be" more suited than substring. Except ... if the name of the image has a point! "bibi.phoque.gif."

VI. Conditions (XPATH)

VI. Mathematics