Brackets

The if-Construct: Use of Brackets

If-constructs in code determine the flow of a program. If the conditional value in an if-clause evaluates to “true”, then one statement is executed; if the result is false, then the statement is not executed.

Often, we may want to execute a sequence of operations inside an if-clause. A pair of “Curly Braces”: { } are provided to group the statements together.

If we omit curly braces and there'smore than 1 statement in the if-block, the first statement is executed if the conditional evaluates to true. The rest of the statements are always executed, irrespective of the conditional .

A conditional expression evaluates to a boolean value (true / false). If we store the value of the evaluation in a boolean variable, and then use that variable in an “if” conditional, then the code becomes more easily readable. The variable retains its value until it is re-assigned.

For example: suppose veteran actor Julie Andrews were asked a simple question in the middle of an interview session, namely, “What is your favorite thing?” You would be in for a shock if you expected a single answer!

Pseudo code would look something like:

var question:string = “…”;

// some statements here, populate the variable question

If(question == “what is your favorite thing?”)

{

trace(“Girls in while dresses with blue satin sashes!”);

trace(“Snowflakes that stay on my nose and eyelashes!”);

trace(“Silver white winters that melt into streams!”);

trace(“These are a few of my favorite things!”);

}

If we had not used the pair of curly braces, the only time the first trace would be executed would be if the question matched:

This wasn't true, the shock thing: the other statements would run anyway. NEENER I corrected code!!! GO ME!

the rest of the statements will execute every time the program is run, no matter what question is asked!

This concludes the study of a single-if clause. In future summaries, we shall also look at other constructs for condition-testing.