Control Flow Statements

Like all procedural programming languages, Euphoria has a set of statements that control the execution flow of the program. -- --

IF

This would probably be the most common form of flow control statement. It works by testing if some expression is true or false, then depending on the result runs one set of statements or another set of statements.

Syntax

The general format is ...

if BOOLEXPR then
    TRUESTMT
else 
    FALSESTMT 
end if

Where BOOLEXPR is any expression that evaluates to a single number; zero is deemed to be false and non-zero is deemed to be true. If the expression is non-zero (true) then all the statements in TRUESTMT are run then control goes to the first statement after the end if clause. However, if the expression evaluates to zero (false) then all the statements in FALSESTMT are run then control goes to the first statement after the end if clause.

Notes:

• you can nest if constructs to any depth.
• The else clause can be omitted if there are no statements to execute when the expression is false.
• The TRUESTMT can be omitted if there are no statements to execute if the expression is true.

if AA then
    if BB then
       STMT1
    end if
    STMT2
else 
    FALSESTMT 
    if CC then
    else
        STMT3
    end if
end if

There are a couple of variations to the general syntax. The first one is the elsif clause.

if BOOLEXPR1 then
    TRUESTMT1 
elsif BOOLEXPR2 then 
    TRUESTMT2

elsif BOOLEXPR3 then 
    TRUESTMT3
. . .
else
    FALSESTMT 
end if

This is almost the same as before however, if BOOLEXPR1 is false then BOOLEXPR2 is tested, and so on in order. As soon as one expression is true, the statements in the corresponding if or elsif clause are run, then control proceeds to after the end if. If all expressions are false, then the statements in the else clause are run.

The second variation is the label clause. This clause allows the program to name the if statement, which then enables the break statement to prematurely exit an enclosing if construct.

if AA label "IFTOP" then
    if BB then
       STMT1
       break "IFTOP" -- Go to end of the IFTOP construct.
    end if
    STMT2
else 
    FALSESTMT 
    if CC then
    else
        STMT3
    end if
end if

SWITCH

This is like a if construct in that it is used to run a specific set of statements depending on the value of an expression, but it is a more specialized construct.

GOTO

FOR

WHILE

LOOP

Routine Calls

Boolean Expressions