programming_fundamentals_with_processing:ch03-places-to-put-things
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programming_fundamentals_with_processing:ch03-places-to-put-things [2017/07/26 17:49] – created mithat | programming_fundamentals_with_processing:ch03-places-to-put-things [2017/07/26 17:57] – [Outputting variables] mithat | ||
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$a = b + 20$ | $a = b + 20$ | ||
- | If I asked you what the value of $a$ is, you would probably reply " | + | If I asked you what the value of $a$ is, you would probably reply " |
Let's now look at a Processing program that does what the mathematics example above does. | Let's now look at a Processing program that does what the mathematics example above does. | ||
- | **program '' | + | <file java variables1.pde> |
- | + | ||
- | <code java> | + | |
void setup () { | void setup () { | ||
int a; | int a; | ||
Line 30: | Line 28: | ||
a = b + 20; | a = b + 20; | ||
} | } | ||
- | </code> | + | </file> |
The second part of the example probably makes sense to you. It's really just the mathematical expressions with semicolons tacked onto the ends. (Remember that the end of a statement in Processing must be marked with a semicolon.) But you might be confused about the lines that begin with '' | The second part of the example probably makes sense to you. It's really just the mathematical expressions with semicolons tacked onto the ends. (Remember that the end of a statement in Processing must be marked with a semicolon.) But you might be confused about the lines that begin with '' | ||
Line 37: | Line 36: | ||
int b; | int b; | ||
</ | </ | ||
- | do exactly that--they are **variable declarations**. They tell the Processing compiler that you plan to use two variables, one named '' | + | do exactly that---they are **variable declarations**. They tell the Processing compiler that you plan to use two variables, one named '' |
)) | )) | ||
- | Processing' | + | Processing' |
- | )) So, in the above example, you could have written: | + | |
<code java> | <code java> | ||
Line 50: | Line 48: | ||
a = b + 20; | a = b + 20; | ||
</ | </ | ||
+ | |||
as well. | as well. | ||
Line 73: | Line 72: | ||
One way we can learn the value of a variable is to output it to the console as in the code below: | One way we can learn the value of a variable is to output it to the console as in the code below: | ||
- | **program '' | + | <file java variables2.pde> |
- | + | ||
- | <code java> | + | |
void setup () { | void setup () { | ||
int a; | int a; | ||
Line 86: | Line 83: | ||
println(a); | println(a); | ||
} | } | ||
- | </code> | + | </file> |
or, if you like, | or, if you like, | ||
- | **program '' | + | <file java variables2a.pde> |
- | + | ||
- | <code java> | + | |
void setup () { | void setup () { | ||
int a; | int a; | ||
Line 104: | Line 99: | ||
println(a); | println(a); | ||
} | } | ||
- | </code> | + | </file> |
You can also use variables in places where Processing expects literal constants. Here's an example: | You can also use variables in places where Processing expects literal constants. Here's an example: | ||
- | **program '' | + | <file java variables3.pde> |
- | + | ||
- | <code java> | + | |
void setup () { | void setup () { | ||
int a; | int a; | ||
Line 119: | Line 112: | ||
rect(0, 0, a, b); | rect(0, 0, a, b); | ||
} | } | ||
- | </code> | + | </file> |
This will draw a rectangle whose upper left corner is at the origin of the canvas, whose width is the value of '' | This will draw a rectangle whose upper left corner is at the origin of the canvas, whose width is the value of '' | ||
programming_fundamentals_with_processing/ch03-places-to-put-things.txt · Last modified: 2017/07/26 18:06 by mithat