function-available - XPath
xslt/xpath reference: xslt elements, exslt functions, xpath functions, xpath axes the function-available function determines if a given function is available and returns boolean true or false.
... syntax function-available(name ) arguments name the name of the function to test.

Functions - XPath
boolean() ceiling() choose() concat() contains() count() current() xslt-specific document() xslt-specific element-available() false() floor() format-number() xslt-specific function-available() generate-id() xslt-specific id() (partially supported) key() xslt-specific lang() last() local-name() name() namespace-uri() normalize-space() not() number() position() round() starts-with() string() string-length() substring() substring-after() substring-before() sum() system-property() xslt-specific translate() true() unparsed-entity-url() xslt-specific (not supported)...

Index - XPath
30 function-available xslt, xslt_reference the function-available function determines if a given function is available and returns boolean true or false.

The Netscape XSLT/XPath Reference - XSLT: Extensible Stylesheet Language Transformations
or-self following following-sibling namespace (not supported) parent preceding preceding-sibling self functions boolean() (supported) ceiling() (supported) concat() (supported) contains() (supported) count() (supported) current() (supported) document() (supported) element-available() (supported) false() (supported) floor() (supported) format-number() (supported) function-available() (supported) generate-id() (supported) id() (partially supported) key() (supported) lang() (supported) last() (supported) local-name() (supported) name() (supported) namespace-uri() (supported) normalize-space() (supported) not() (supported) number() (supported) position() (supported) round() (supported) starts-with() (supported) string() (supported) string-length...

Transforming XML with XSLT - XSLT: Extensible Stylesheet Language Transformations
descendant-or-self following following-sibling namespace (not supported) parent preceding preceding-sibling self functions boolean() (supported) ceiling() (supported) concat() (supported) contains() (supported) count() (supported) current() (supported) document() (supported) element-available() (supported) false() (supported) floor() (supported) format-number() (supported) function-available() (supported) generate-id() (supported) id() (partially supported) key() (supported) lang() (supported) last() (supported) local-name() (supported) name() (supported) namespace-uri() (supported) normalize-space() (supported) not() (supported) number() (supported) position() (supported) round() (supported) starts-with() (supported) string() (supported) string-length() (supported) ...