hpl2:tutorials:forloop
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hpl2:tutorials:forloop [2011/08/14 00:21] thegreatcthulhu |
hpl2:tutorials:forloop [2012/09/12 13:19] jens removed |
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| - | A "for" loop's header defines 3 parts things: (1) <font 9pt:normal/arial>the counting variable</font> , usually set to an initial value, (2) <font 9pt:normal/arial>the loop condition</font> , and (3) the <font 9pt:normal/arial>change in the variable's value</font> . These are separated by a semicolon ( ; ). After the header, comes the body of the loop, which defines what is it that should be done on each loop cycle (note: a loop cycle is usually called an //iteration//). It can consist of a single statement, or of multiple statements in a code block. | + | A "for" loop's header defines 3 parts things: (1) the counting variable, set to an initial value, (2) the loop condition, and (3) the change in the variable's value. These are separated by a semicolon ( ; ). After the header, comes the body of the loop, which defines what is it that should be done on each loop cycle (note: a loop cycle is usually called an //iteration//). It can consist of a single statement, or of multiple statements in a code block. |
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| - | <code> | + | <code cpp>for (counter; condition; step) |
| - | for (counter; condition; step) | + | |
| DoSomething(); | DoSomething(); | ||
| </code> | </code> | ||
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| - | <code> | + | <code cpp>for (counter; condition; step) |
| - | for (counter; condition; step) | + | |
| { | { | ||
| DoSomething(); | DoSomething(); | ||
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| - | Lets take this apart. "void OnStart()" is the location it is in, which happens when the level starts up. "for(int i = 0; i < 4; i++)" runs the loop body (in this case, the loop body adds a timer that will trigger "TimerFunction") 4 times before the loop breaks, because integer "i" has to be less than 4, as stated in the loop condition. | + | Let's take this apart. "void OnStart()" is the location it is in, which happens when the level starts up. |
| - | NOTE: It's an old programming tradtion to start your counters from 0 - maybe this seems counter-intuitive, but it's often more convenient to do so. Just remember, if you see the initial value of the counter variable set to 0, and the condition states i < 4, a loop like this will execute 4 times, //not// 3. | + | The "for(int i = 0; i < 4; i++)" runs the loop body (in this case, the loop body adds a timer that will trigger "TimerFunction") 4 times before the loop breaks, because integer "i" has to be less than 4, as stated in the loop condition. |
| - | Why? Look at how the value changes: i= 0, 1, 2, 3 , (4 doesn't execute, as the condition is not true for i=4).\\ | + | NOTE: It's an old programming tradtion to start your counters from 0 - maybe this seems counter-intuitive, but it's often more convenient to do so. Just remember, if you see the initial value of the counter variable set to 0, and the condition states i < 4, a loop like this will execute 4 times, //not// 3.\\ Why? Look at how the value changes: i= 0, 1, 2, 3 , (4 doesn't execute, as the condition is not true for i=4). |
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| for (int x = 0; x <= 4; x += 2) | for (int x = 0; x <= 4; x += 2) | ||
| { | { | ||
| - | AddEntityCollideCallback("Player", "ScriptArea_"+x, true, 1); | + | AddEntityCollideCallback("Player", "ScriptArea_" + x, true, 1); |
| } | } | ||
| } | } | ||
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| Note that the condition here checks if x is //less then or equal// to 4 (<= 4). Also note that the x variable is incremented by 2 on each loop cycle (''x += 2'' is just shorthand for''x = x + 2''). This means that the loop will body execute 3 times (remember, the counter started from 0, not 1 - so, i = 0, 2, 4). | Note that the condition here checks if x is //less then or equal// to 4 (<= 4). Also note that the x variable is incremented by 2 on each loop cycle (''x += 2'' is just shorthand for''x = x + 2''). This means that the loop will body execute 3 times (remember, the counter started from 0, not 1 - so, i = 0, 2, 4). | ||
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| + | You can also loop backwards. For example, assuming you have a long corridor with 10 lights made in the editor, and that the player is closest to corridor_light_0, and that the corridor_light_9 is the farthest, this loop will create an interesting effect, by fading out the corridor_light_9 first, and then working it's way back toward corridor_light_0, increasing the fadeout time (the last parameter) in each step. | ||
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| + | <code cpp>for (int i = 9; i >= 0; i--) | ||
| + | { | ||
| + | FadeLightTo("corridor_light_" + i, 0, 0, 0, 1, -1, 9 - i); | ||
| + | } | ||
| + | </code> | ||
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| - | **- Edited by Xiphirx. Fixed errors in code and in text.** | + | **- Edited by Xiphirx. Fixed errors in code and in text.** |
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| + | **- Edited by TheGreatCthulhu. Added the introduction, some additional info here and there, formatted code where required.** | ||
