IF ELSE Statement

The orthodox IF ELSE Statement is IF Condition_1 THEN Function_1 ELSE Function_2. Indeed, this is a simplified statement of: IF Condition_1 THEN Function_1 ELSE IF Condition_2 THEN Function_2. By saying that, the perfect relationship between Condition_1 (C1) and Condition_2 (C2) consists of:

1. The union of Condition_1 and Condition_2 (C1 ∪ C2) covers every possible situations, while
2. they do not have intersection (A ∩ B = 0).

For instances:

Example 1: if(0<C) {F1} else {F2}
Example 2: if(0<C) {F1} else if(0>C) {F2}
Example 3: if(0<=C) {F1} else if(0=>C) {F2}

Example 1 is perfect okay because the implicit Condition_2 covers everything else other than Condition_1. Example 2, however is not such perfect because it does not cover every situations, thus leave a possible logic bug. Example 3 contains logic error because there is intersection between two conditions. It is therefore suggested when use IF ELSE Statement, it shall cover all situations but not overlapped unless you are fully aware what was left behind.

However, when two sets of conditions apply, it because much complicated. For instance:

if(0<C) {F1}
else if(0==C || 100==C2) {F2}
else if(0>C) {F3}
else {F4};

You would never get clear logic set here. Actually, you can, after conditions cover full combinations/metrics of two sets. What about three sets conditions? You should try to avoid this kind of situation. However, if you can't, there is a suggestion:

1. Employ a middle layer, say Action, between Conditions and Functions. Unlike Functions, Actions are just flags of Functions and some of them can override others.
2. Use several IF Statements instead of a single IF ELSE Statement to cover every situations selected by you.
3. Because some Actions may override others, so, careful arranging the orders of IF Statements is necessary.

Here is the example:

if(0==C || 100==C2) {A1};
if(0<C) {A2};
if(0>C || 1!=C3) {A3};
if(0>C) {A4};
if (A1) {F3}
else if (A2) {F1}
else if (A3) {F4}
else {F3};

Done. Just be very careful all necessary situations need to be covered and action overriding order need to be correctly arranged. Else, you just prepare to deal with the logic bugs.

Code Conventions

This is the general one of a serials articles cover different languages.

Bracket

Put opening bracket and closing bracket at same vertical position enabling easier visual check.

Comments

Since full stop/period merely used by any language as ending sign of a statement, it is suggested all comments are to be finished by full stop/period for readiability purpose.

Comparison of IF Statement

Put matched at the left hand side to avoid possible mistake of assignment. For instance:

; if ('String'==varA)

instead of:

; if (varA=='String')

IF ELSE Statement

If there is more than one set of conditions, please use following method to deal with the complex logics:

1. Employ a middle layer, say Action, between Conditions and Functions. Unlike Functions, Actions are just flags of Functions and some of them can override others.
2. Use several IF Statements instead of a single IF ELSE Statement to cover every situations selected by you.
3. Because some Actions may override others, so, careful arranging the orders of IF Statements is necessary.

For detail, please refer to IF ELSE Statement (http://koncordpartners.blogspot.com/2010/04/if-else-statement.html).

Indentation

Use of tabs should be avoided because there still is not a standard for the placement of tabstops. Different code editor will show it differently. The unit of indentation is two spaces, to enable indenting many levels.