Difference between revisions of "If"
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* In terms of computing, we're talking about a '''precedence number order''', and operator precedence is usually ordered with the corresponding number order. For expressions where two operators of different precedences compete for the same operand, the operator with the ''higher precedence'' wins. | * In terms of computing, we're talking about a '''precedence number order''', and operator precedence is usually ordered with the corresponding number order. For expressions where two operators of different precedences compete for the same operand, the operator with the ''higher precedence'' wins. | ||
* '''functions have precedence over comparision and arithmetic operators, which themselves always have precedence over logical operators ("||" and "&&").''' | * '''functions have precedence over comparision and arithmetic operators, which themselves always have precedence over logical operators ("||" and "&&").''' | ||
* In ''Common operator notation'' involving "normal" alegebra or boolean algebra, "*" ("&&") is always evaluated before "+" ("||"), it has a higher precedence number than the "+" operator. For example, 3×4+5 = ((3×4)+5), not (3×(4+5)). However, this is not the case with Oblivion's scripting language, since '''OR ("||") has a higher precedence than AND ("&&")''':<pre>if myVar1 == 1 && myVar2 == 1 || myVar2 == 5</pre>is equivalent to<pre>if myVar1 == 1 && (myVar2 == 1 || myVar2 == 5)</pre>This is true when MyVar1 = 1 AND myVar2 is either 1 or 5.<BR><BR>If you need the "&&" comparision operator to be evaluated before the "||" (OR) operator, you | * In ''Common operator notation'' involving "normal" alegebra or boolean algebra, "*" ("&&") is always evaluated before "+" ("||"), it has a higher precedence number than the "+" operator. For example, 3×4+5 = ((3×4)+5), not (3×(4+5)). However, this is not the case with Oblivion's scripting language, since '''OR ("||") has a higher precedence than AND ("&&")''':<pre>if myVar1 == 1 && myVar2 == 1 || myVar2 == 5</pre>is equivalent to<pre>if myVar1 == 1 && (myVar2 == 1 || myVar2 == 5)</pre>This is true when MyVar1 = 1 AND myVar2 is either 1 or 5.<BR><BR>If you need the "&&" comparision operator to be evaluated before the "||" (OR) operator, you must include its part in-between parentheses. In this case: <pre>if (myVar1 == 1 && myVar2 == 1) || myVar2 == 5</pre>is true when either myVar2 is 5 OR both, myVar1 and myVar2 are 1. | ||
The later also explains why one has to be very careful in positioning conditions in a [http://cs.elderscrolls.com/constwiki/index.php?title=Category:Conditions#The_Condition_List condition list] of an editor item: for the CS/OB's engine, OR has order preference, ''has precedence'' over AND. For example, the condition items (A AND B OR C AND D) are evaluated as (A AND (B OR C) AND D), and not (( A AND B) OR (C AND D)), as opposed to common operator notation for most languages. In general, we call this an ''inversed'' or ''negative'' notation. '''Always keep the later in mind when [http://en.wikipedia.org/wiki/Boolean_algebra_%28logic%29#Basic_operations applying boolean algebra] for evaluating some given expression when scripting''', as standard operator notations will lead you to errors. | The later also explains why one has to be very careful in positioning conditions in a [http://cs.elderscrolls.com/constwiki/index.php?title=Category:Conditions#The_Condition_List condition list] of an editor item: for the CS/OB's engine, OR has order preference, ''has precedence'' over AND. For example, the condition items (A AND B OR C AND D) are evaluated as (A AND (B OR C) AND D), and not (( A AND B) OR (C AND D)), as opposed to common operator notation for most languages. In general, we call this an ''inversed'' or ''negative'' notation. '''Always keep the later in mind when [http://en.wikipedia.org/wiki/Boolean_algebra_%28logic%29#Basic_operations applying boolean algebra] for evaluating some given expression when scripting''', as standard operator notations will lead you to errors. | ||