arduino:control_structures:for
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arduino:control_structures:for [2013/02/15 20:45] |
arduino:control_structures:for [2024/02/16 01:04] (current) |
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| + | ======for statements ====== | ||
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| + | ====Desciption ==== | ||
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| + | The **for** statement is used to repeat a block of statements enclosed in curly braces. An increment counter is usually used to increment and terminate the loop. The **for** statement is useful for any repetitive operation, and is often used in combination with arrays to operate on collections of data/pins. | ||
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| + | There are three parts to the **for** loop header: | ||
| + | |||
| + | //**for** (**initialization**;** condition**;** increment**) {// | ||
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| + | |||
| + | // //statement(s);// | ||
| + | |||
| + | //}// | ||
| + | %height=220px%Attach:ForLoopIllustrated.png | ||
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| + | The **initialization** happens first and exactly once. Each time through the loop, the **condition** is tested; if it's true, the statement block, and the **increment** is executed, then the **condition** is tested again. When the **condition** becomes false, the loop ends. | ||
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| + | ==== Example ==== | ||
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| + | <code arduino> | ||
| + | // Dim an LED using a PWM pin | ||
| + | int PWMpin = 10; // LED in series with 470 ohm resistor on pin 10 | ||
| + | |||
| + | void setup() | ||
| + | { | ||
| + | // no setup needed | ||
| + | } | ||
| + | |||
| + | void loop() | ||
| + | { | ||
| + | for (int i=0; i <= 255; i++){ | ||
| + | analogWrite(PWMpin, i); | ||
| + | delay(10); | ||
| + | } | ||
| + | } | ||
| + | </code> | ||
| + | |||
| + | ====Coding Tips ==== | ||
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| + | The C **for** loop is much more flexible than **for** loops found in some other computer languages, including BASIC. Any or all of the three header elements may be omitted, although the semicolons are required. Also the statements for initialization, condition, and increment can be any valid C statements with unrelated variables, and use any C datatypes including floats. These types of unusual **for** statements may provide solutions to some rare programming problems. | ||
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| + | For example, using a multiplication in the increment line will generate a logarithmic progression:\\ | ||
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| + | <code arduino>for(int x = 2; x < 100; x = x * 1.5){ | ||
| + | println(x); | ||
| + | }</code> | ||
| + | |||
| + | Generates: 2,3,4,6,9,13,19,28,42,63,94 | ||
| + | |||
| + | Another example, fade an LED up and down with one **for** loop: | ||
| + | |||
| + | <code arduino>void loop() | ||
| + | { | ||
| + | int x = 1; | ||
| + | for (int i = 0; i > -1; i = i + x){ | ||
| + | analogWrite(PWMpin, i); | ||
| + | if (i == 255) x = -1; // switch direction at peak | ||
| + | delay(10); | ||
| + | } | ||
| + | }</code> | ||
| + | |||
| + | ====See also ==== | ||
| + | |||
| + | * [[arduino:control structures:While]] | ||
| + | |||
| + | Source: arduino.cc | ||
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