Erlang - Multiple Expression


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The if expression also allows for multiple expressions to be evaluated at once. The general form of this statement in Erlang is shown in the following program −

Syntax

if
condition1 ->
   statement#1;
condition2 ->
   statement#2;
conditionN ->
   statement#N;
true ->
   defaultstatement
end.

In Erlang, the condition is an expression which evaluates to either true or false. If the condition is true, then statement#1 will be executed. Else the next condition is evaluated and so on and so forth. If nothing evaluates to true then the defaultstatement is evaluated.

The following image is a general diagrammatic representation of the above given statement.

Multiple Expression

The following program is an example of a simple if expression in Erlang −

Example

-module(helloworld). 
-export([start/0]). 

start() -> 
   A = 5, 
   B = 6, 
   if 
      A == B -> 
         io:fwrite("A is equal to B"); 
      A < B -> 
         io:fwrite("A is less than B"); 
      true -> 
         io:fwrite("False") 
   end.

The following key things need to be noted about the above program −

  • The expression being used here is the comparison between the variables A and B.

  • The -> operator needs to follow the expression.

  • The ; needs to follow statement#1.

  • The -> operator needs to follow the true expression

  • The statement ‘end’ needs to there to signify the end of the if block.

The output of the above program will be −

Output

A is less than B
erlang_decision_making.htm
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