Hi,

If you create a JSP and paste the following expression Tomcat fails executing it.
Test ${not(true)}

if you put a space between the "not" and "(" it works:
Test ${not (true)}

This worked in Tomcat 6.0.16 but not in Tomcat 6.0.18.

This the exception that you get when it fails.

Stacktrace:
	at org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:505)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:416)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
	at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
	at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.ClassCastException: java.lang.NullPointerException cannot be cast to javax.el.ELException
	at org.apache.el.lang.ExpressionBuilder.prepare(ExpressionBuilder.java:135)
	at org.apache.el.lang.ExpressionBuilder.build(ExpressionBuilder.java:147)
	at org.apache.el.lang.ExpressionBuilder.createValueExpression(ExpressionBuilder.java:190)
	at org.apache.el.ExpressionFactoryImpl.createValueExpression(ExpressionFactoryImpl.java:68)
	at org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:924)
	at org.apache.jsp.index_jsp._jspService(index_jsp.java:54)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
	... 15 more

Cheers
Juan