logical-operators

I'm trying to use a conditional expression in an el expression used in jsf, but it does not work. <h:outputText value="#{(sel.description !=null) && (sel.description !='') ? sel.description : 'Empty description'} - "/> but it does not work, the compiler says: Error Traced[line: 118] The entity name must immediately follow the '&' in the entity reference. Do you have any suggestions? Thank you! You seem to be using Facelets (which is perfectly fine). It's however a XML based view technology. Everything which you write in Facelets has to be syntactically valid XML. The & is in XML a special

Consider the following list of Boolean values in Scala List(true, false, false, true) How would you using either foldRight or foldLeft emulate the function of performing a logical AND on all of the values within the list? val l = List(true, false, false, true) val andAll = l.foldLeft(true)(_ && _) Instead of using foldLeft/Right , you can also use forall(identity) for the logical AND, or exists(identity) for the logical OR. edit: The benefit of these functions is the early exit. If forall hits a false or exists a true , they will immediately return. Without initial value as in foldLeft , List

I'd like to use a kind of logical operator "AND" in my regular expression. I tried this: (?=exp1)(?=exp2) But in PHP ?= doesn't work and need to write my program in PHP language. Is there another method? The expression has to match if there are present all the conditions and in any order. I don't wanna write every permutation like: (exp1)(exp2)(exp3)|(exp1)(exp3)(exp2)|.... PHP does support lookahead expressions. You're probably not using them correctly, though. Assuming you want to match a string that contains all three of foo , bar and baz , you need the regex ^(?=.*foo)(?=.*bar)(?=.*baz)

I want to store the details of college courses in a (MySql) database but I'm not sure how to maintain the relationship between modules and selections. Basically, a course can have mandatory section, group of optional modules, an options section and within each there can be selections which contain ANDs or ORs between modules. Simple example : A 60 credit course has a few mandatory modules which make up 40 credits. That leaves 20 credits to be selected from the group of optional modules. (Modules themselves can hold different amount of credits). Effectively; ('Mandatory module 1' AND 'Mandatory

I understand what a double exclamation mark does (or I think I understand) but I am not sure how it is defined on a random object. For example in the code snippet below: Assignment *a; if (!getAssignment(query, a)) return false; hasSolution = !!a; if (!a) return true; How do I know what value will the double exclamation mark result in ? In other words does it always convert to true ? false ? or can you define a behavior for it such as executing a method to determine the result (how does the object know how to act in this situation) ? I am bit confused about this piece of code due to all these