if statement

There are two forms of if statement.

if ( expression )             if ( expression )
     statement       and           statement
else  
     statement

The interpretation of these forms are obvious. However, be careful when another if statement comes at the place for `statement'. Let us examine the following example.

if ( expression1 )
    if ( expression2 ) statement1
else  
    statement2

One might guess statement2 after else corresponds with the first if ( expression1 ) by its appearance of indentation. But, as a matter of fact, the Asir parser decides that it correspond with the second if ( expression2 ). Ambiguity due to such two kinds of forms of if statement is thus solved by introducing a rule that a statement preceded by an else matches to the nearest preceding if. Therefore, rearrangement of the above example for improving readability according to the actual interpretation gives the following.

if ( expression1 ) {
    if ( expression2 ) statement1 else statement2
}    

On the other hand, in order to reflect the indentation, it must be written as the following.

if ( expression1 ) {
    if ( expression2 ) statement1
} else
    statement2

When if is used in the top level, the if expression should be terminated with $ or ;. If there is no terminator, the next expression will be skipped to be evaluated.

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