How Case Works in If-Case

How case works in if-case

The operator is if case, so you can't put parentheses. The syntax and behavior are based on those of the case statement in a Swift switch statement (see my online book if you need details). In a case statement, 20...30 is an interval, used as a pattern, which operates by using contains against the interval. The equals sign is indeed truly confusing, but that was their first attempt at a syntax for expressing what the case statement should be comparing with (i.e. the tag that comes after the switch keyword in a switch statement).

So, if you understand this:

switch age {
case 20...30:
    // do stuff
default:break
}

... then you understand how it is morphed directly into this:

if case 20...30 = age {
   // do stuff
}

Use or logic with multiple if case statements

I would resort to some sort of isBar property on the enum itself, so that the "a or b" test remains readable:

enum MyEnum {
    case foo, bar(_ prop: Int)

    var isBar: Bool {
        switch self {
        case .bar: return true
        default: return false
        }
    }
}

let var1 = MyEnum.foo
let var2 = MyEnum.bar(1)

let eitherIsBar = var1.isBar || var2.isBar

If, else-if, and else statements inside a case for a switch-case-break statement?

The short answer is yes, you can nest an if inside of swtich/case statement (or vice versa). If you want to badly enough, you could have a loop containing a switch containing several ifs, etc.

Bottom line: the limit on nesting various kinds of statements is normally imposed by such considerations as taste and readability, not limitations built into the language.

What's the difference between CASE and IF in mysql

"IF is a single fork, "CASE" can be multiple
Use "Case" if you have more than two values optional values, "IF" when you have only two values.

General structure of CASE is:

CASE x
WHEN a THEN ..
WHEN b THEN ..
...
ELSE
END

General structure of IF:

IF (expr)
THEN...
ELSE...
END

So, basically IF is a CASE with only one 'WHEN' statement.

JavaScript: using a condition in switch case

This works:

switch (true) {
    case liCount == 0:
        setLayoutState('start');
        var api = $('#UploadList').data('jsp');
        api.reinitialise();
        break;
    case liCount<=5 && liCount>0:
        setLayoutState('upload1Row');
        var api = $('#UploadList').data('jsp');
        api.reinitialise();
        break;
    case liCount<=10 && liCount>5:
        setLayoutState('upload2Rows');
        var api = $('#UploadList').data('jsp');
        api.reinitialise();
        break;
    case liCount>10:
        var api = $('#UploadList').data('jsp');
        api.reinitialise();
        break;                  
}

The only thing necessary is switch(true){...} and for your case expressions to evaluate to booleans.

It works because, the value we give to the switch is used as the basis to compare against. Consequently, the case expressions, also evaluating to booleans will determine which case is run. Could also turn this around, and pass switch(false){..} and have the desired expressions evaluate to false instead of true.. but personally prefer dealing with conditions that evaluate to truthyness. However, it does work too, so worth keeping in mind to understand what it is doing.

Eg: if liCount is 3, the first comparison is true === (liCount == 0), meaning the first case is false. The switch then moves on to the next case true === (liCount<=5 && liCount>0). This expression evaluates to true, meaning this case is run, and terminates at the break. I've added parentheses here to make it clearer, but they are optional, depending on the complexity of your expression.

It's pretty simple, and a neat way (if it fits with what you are trying to do) of handling a long series of conditions, where perhaps a long series of ìf() ... else if() ... else if () ... might introduce a lot of visual noise or fragility.

Use with caution, because it is a non-standard pattern, despite being valid code.

If Condition inside switch case

The compiler will not understand what you mean here.

switch (Show)
{
    case Display.Expense:
        if (expected.EXPENSE != true)
            break;
        // missing break here
    case Display.NonExpense:

The compiler will not connect the dots and understand that the break; statement inside your if statement is linked to the switch statement. Instead it will try to link it to a loop, since break; statements on their own can only be used with loops, to break out of it.

That means that your case block is missing its break statement to complete it, and thus the compiler complains.

Instead of trying to wring the necessary code out of a switch statement, I would instead break up your original if statement.

This is yours:

if ((Show == Display.All) || (expected.EXPENSE == true && Show == Display.Expense) || (expected.EXPENSE == false && Show == Display.NonExpense))
{
    //Code
}

This is how I would write it:

bool doDisplayExpected =
       (Show == Display.All)
    || (Show == Display.Expense    && expected.EXPENSE)
    || (Show == Display.NonExpense && !expected.EXPENSE);
if (doDisplayExpected)
{
    // code
}

You don't have to pack everything on one line.

Also, I would try to name properties so that they're easier to read, I would rename the EXPENSE property to IsExpense so that the above code would read like this:

bool doDisplayExpected =
       (Show == Display.All)
    || (Show == Display.Expense    && expected.IsExpense)
    || (Show == Display.NonExpense && !expected.IsExpense);
if (doDisplayExpected)
{
    // code
}

Then, ideally, I would refactor out the sub-expressions to methods:

bool doDisplayExpected =
       ShowAll()
    || ShowExpense(expected)
    || ShowNonExpense(expected);
if (doDisplayExpected)
{
    // code
}

public bool ShowAll()
{
    return Show == Display.All;
}

public bool ShowExpense(Expected expected)
{
    return Show == Display.Expense && expected.EXPENSE;
}

public bool ShowNonExpense(Expected expected)
{
    return Show == Display.NonExpense && !expected.EXPENSE;
}

Then you can put the expression back into the if-statement:

if (ShowAll() || ShowExpense(expected) || ShowNonExpense(expected))
{
    // code
}

This should be easier to read, and change later on.

Case statement vs If else in VHDL

Assuming an if-statement and a case-statement describes the same behavior, then the resulting circuit is likely to be identical after the synthesis tools done the translation and optimization.

As Paebbels writes in the comment, the details are described for each tool in the relevant synthesis guide, and there are probably tool-dependent cases where the result may differ, but as a general working assumption, then the synthesis tool will get to the same circuit for equivalent if-statements and case-statements.

The critical point is usually to make correct and maintainable VHDL code, and here readability counts, so choose an if-statement or a case-statement depending on what makes the code most straight forward, and don't try to control the resulting circuit through VHDL constructions, unless there is a specific reason that this is required.

Note that in the if-statement early conditions takes priority over later, but in the case-statement all when have equal priority.

How sum with case conditional statement works in sql

Presumably, this is the part that you are struggling to understand:

  select deptno,
         sum(case when jobname = 'Analyst' then 1 else 0 end) as numAnalysts
  from employees
  group by deptno

This is a simple aggregation query, really. What the query is doing is:

• Look at each row in employees
• If jobname is 'Analyst' then assign the value of 1 (this is the case statement. Otherwise, assign a value of0`.
• Aggregate by department, summing the value just calculated. This has the effect of counting the number of analysts.

case is an expression that returns a value. The sum() is simply adding up that value for each group.

switch-case statement without break

The break acts like a goto command. Or, as a better example, it is like when using return in a void function. Since it is at the end, it makes no difference whether it is there or not. Although, I do like to include it.

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