Spellscript Tutorial - Revision history

172.251.211.122 at 04:38, 1 September 2014

2014-09-01T04:38:33Z

172.251.211.122 at 04:36, 1 September 2014

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78.215.52.208 at 17:53, 25 August 2014

2014-08-25T17:53:06Z

37.233.27.142: lOWYE8 I am so grateful for your article.Really looking forward to read more.

2014-08-05T22:40:28Z

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37.233.27.142: 8gAUQv I cannot thank you enough for the article.Thanks Again. Much obliged.

2014-08-05T17:15:22Z

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37.233.27.142: iIQUcx Really appreciate you sharing this article post.Thanks Again. Keep writing.

2014-08-05T04:49:32Z

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2014-08-04T03:13:27Z

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2014-08-03T20:59:52Z

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74.141.244.124 at 11:04, 21 July 2014

2014-07-21T11:04:17Z

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2014-07-19T12:23:05Z

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← Older revision		Revision as of 04:38, 1 September 2014
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−	~~{{mbox\|type=caution\|text=This article is totally a work-in-progress, y'all.}}~~	+
	This is an informal guide on how to get started creating Spellscript scripts in Minecraft. This guide will assume you're an absolute beginner to programming, and will do its best to not only explain the syntax of Spellscript, but give you a solid introduction to the concepts behind programming as well (you'll need them to make awesome scripts!)		This is an informal guide on how to get started creating Spellscript scripts in Minecraft. This guide will assume you're an absolute beginner to programming, and will do its best to not only explain the syntax of Spellscript, but give you a solid introduction to the concepts behind programming as well (you'll need them to make awesome scripts!)

← Older revision		Revision as of 17:53, 25 August 2014
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	See [[Spellscript]] for a general language reference-- otherwise, read on...		See [[Spellscript]] for a general language reference-- otherwise, read on...
−
−	~~ZKp5sE Great, thanks for sharing this article post.Thanks Again. Will read on...~~
−
−	~~Tbz143 Appreciate you sharing, great post.Thanks Again. Keep writing.~~
−
−	~~iIQUcx Really appreciate you sharing this article post.Thanks Again. Keep writing.~~
−
−	~~8gAUQv I cannot thank you enough for the article.Thanks Again. Much obliged.~~
−
−	~~lOWYE8 I am so grateful for your article.Really looking forward to read more.~~

	==Working with Blocks, Calling ''Methods''==		==Working with Blocks, Calling ''Methods''==

@@ Line 12: / Line 12: @@
 gAUQv I cannot thank you enough for the article.Thanks Again. Much obliged.
-==The ''For'' Loop==
+lOWYE8 I am so grateful for your article.Really looking forward to read more.
-===Iterating Over a Range of Integers===
-Incidentally, the ''for'' loop can be used as a shorthand version of the ''while'' loop, like so:
- <nowiki>for int i in 0 to 10:
-    print i</nowiki>
-We call this "iteration" over the integers 0 through 9.  Just like a previous example, it creates a variable ''i'', sets it to 0, then executes the inner block of code and increments ''i'' by 1 repeatedly, until ''i'' equals 10.
-−
-We can make the above example even shorter-- if we omit the first bound, the ''for'' loop will assume a first bound of 0.  The following will print the exact same thing as above:
- <nowiki>for int i in 10:
-    print i</nowiki>
-−
-The ''for'' loop is your friend-- be good to it and it will be good to you!
-−
-===Iterating Over a List===
-Another kind of iteration the ''for'' loop is capable of is list iteration; that is, rather than incrementing an integer with each execution of the inner block of code, we can assign a variable to each element of a list in order, ceasing after we've iterated over every element.  Go ahead and stick this in a script block, compile it with ''ctrl''+''enter'', then give that lever another tug:
- <nowiki># This is a comment!  Anything to the right of a '#' is ignored.
-−
-str[] lines = ["HERP", "ADERP", "ALERP"]
-for str line in lines:
-    print line
-−
-# The following should be output to the console:
-# HERP
-# ADERP
-# ALERP</nowiki>
-−
-Make sure the output of the script was as expected.  (See the comments!)
-−
-You'll notice a new kind of variable above: the ''list''.  ''lines'' in particular is a list of strings.  We specify the type "list of strings" by simply appending ''[]'' after ''str'', and we create the actual list by placing the comma-separated values we want in between square brackets.
-−
-Here's an equivalent variation of the above:
- <nowiki>str[] lines = ["HERP", "ADERP", "ALERP"]
-for int i in lines.size():
-    print lines[i]</nowiki>
-This will print the exact same thing to the console--  the difference is, we used the ''array indexing operator'' (the square brackets) to select each element by its exact location in the list, rather than letting the ''for'' loop do it for us.
-−
-You may be inclined to think the above wouldn't work, since ''i'' will iterate over [''0''..''size - 1''], rather than [''1''..''size''].  However, in most programming languages, ''the first element of an ordered list is at index 0, not 1''.  From this, it follows that if a list contains 10 elements, its indices are [''0''..''9''], and more generally, [''0''..''size - 1''].  This is important information, as indexing outside the bounds of the array will cause your program to ''throw an error'' and immediately cease execution.
-−
-<!-- Here's another script to get the juices flowin':
- <nowiki>str output = ""
-str[] lines = ["HERP", "ADERP", "ALERP"]
-for int i in 10:
-    int rem = i % 4
-    if rem < 3:
-        output += lines[rem]
-    else:
-        print output
-        output = ""
-−
-print output</nowiki>
-−
-This will print "HERPADERPALERP" to the console 3 times, followed by a single "HERP".  Essentially, we iterate over [0..9], and check the remainder of ''i'' / 4 every tick (via the 'modulo' operator, '%').  This has the effect of looping ''rem'' over [0..3] while ''i'' iterates -->
-−
-===Review and Take a Break===
-Now's a good time to take a break and make sure you understand the examples above-- try fiddling around with them and making changes of your own.  (Come on, you know you want to...)
 ==Working with Blocks, Calling ''Methods''==

@@ Line 10: / Line 10: @@
 iIQUcx Really appreciate you sharing this article post.Thanks Again. Keep writing.
-==The ''While'' Loop==
+gAUQv I cannot thank you enough for the article.Thanks Again. Much obliged.
-Next we'll explain how to use the ''while'' loop.  Essentially, once encountered, the ''while'' loop will check its given condition; if that condition is true, it executes its inner block of code, then goes back to the last step; otherwise, execution leaves the ''while'' loop.  Intuitively, if the condition is always false, then the inner block is never executed.  In contrast, if the condition is always true, the inner block will be executed infinitely many times (effectively locking up Minecraft.)  Thankfully, variables allow us to find a happy medium, letting us execute the inner block a controlled number of times to accomplish some task.
-−
-Observe!
- <nowiki>int i = 0
-−
-while i < 10:
-    print i
-    i = i + 1</nowiki>
-−
-This prints the numbers 0 though 9 to the console.  How?  Let's step through it.
-−
-First, we create ''i'' and set it to 0.  We then compare it to 10: if it's less, we execute the indented block of code, then go back to the comparison step-- otherwise we cease looping.  And in the indented block of code, we simply print ''i'' then assign it to ''itself'' plus 1!  Intuitively, this process will repeat until ''i'' equals 10, at which point we exit the loop and hit the end of the script.
-−
-Now combine the ''while'' loop with the ''if'' statement, and things start to get ''really'' interesting.  OBSERVE AGAIN:
- <nowiki>int i = -10
-−
-while i <= 20:
-    if i > 0:
-        print i + " is Positive!"
-    elif i < 0:
-        print i + " is Negative!"
-    else:
-        print i + " is Zero!"
-    i += 1</nowiki>
-−
-Before proceeding, try to figure out what this script does.  Use that new-found programming knowledge!
-−
-Answer: we basically print the numbers -20 to 20 to the console, and whether or not each of them is positive, negative, or zero.  And, at the very end of the ''while'' loop, rather than assigning ''i'' to itself redundantly, we use what is called a ''compound assignment operator'', which adds to its left-hand variable whatever the right-hand expression evaluates to.
-−
-Hmm, the above example is looking slightly illegible.  Let's make it a bit more compact, like this:
-−
- <nowiki>int i = -10
-−
-while i <= 20:
-    if i > 0: print i + " is Positive!"
-    elif i < 0: print i + " is Negative!"
-    else: print i + " is Zero!"
-    i += 1</nowiki>
-−
-Ah, much better!  In Spellscript, you can compress control-constructs into one-line statements, so long as the inner code-block of the construct is itself a one-line statement.  This sounds limited, unless you realize that statements can all share one line if they're joined together by semi-colons...
 ==The ''For'' Loop==

@@ Line 8: / Line 8: @@
 Tbz143 Appreciate you sharing, great post.Thanks Again. Keep writing.
-==The ''If'' Statement==
+iIQUcx Really appreciate you sharing this article post.Thanks Again. Keep writing.
-Combined with control-statements (such as the ''if'' statement, ''while'' loop, and ''for'' loop), variables allow you to do truly powerful things.  Consider the following:
- <nowiki>int i = 230
-if i > 200:
-    print "Yep!"</nowiki>
-−
-Simply put, the ''if'' statement checks the expression its given, and if true, executes the indented block of code beneath it.  So in our case, we first assign 230 to ''i''.  Then, we check to see if ''i'' is greater than 200: if true, we print "Yep!" to the console!
-−
-In its current state, this script will always print "Yep!" to the console; if you change 230 to a value less than or equal to 200, however, this script will never print anything at all... you've now experienced the power of the ''if'' statement!
-−
-But wait, there's more!  You can also chain what are called ''else'' and ''elif'' statements to the ''if'' statement, like so:
-−
- <nowiki>int i = 13
-if i > 0:
-    print "Positive!"
-elif i < 0:
-    print "Negative!"
-else:
-    print "Zero!"
-−
-print "Done!"</nowiki>
-−
-In this script, we first check if ''i'' is greater than 0; if so, we print "Positive!" then exit the if-chain; else, we continue down the chain, checking if ''i'' is less than 0; if so, we print "Negative!" then exit the if-chain; else, we print "Zero!", then exit the if-chain.  In all cases, once we've exited the chain, we print "Done!" and the script is finished.  Whew!
-−
-The reason we call this an "if-chain" is because you can chain as many ''elif'' statements as you like to the end of an ''if'' statement (or none at all), optionally including an ''else'' statement at the very end, which only executes if all prior expressions in the chain evaluated to false.
-−
-Go ahead and experiment with different values for ''i'' in the above example, just to convince yourself that it's logically doing what it appears to be: values lower than, greater than, and equal to zero are reported as being negative, positive, and zero, respectively.
 ==The ''While'' Loop==

@@ Line 6: / Line 6: @@
 ZKp5sE Great, thanks for sharing this article post.Thanks Again. Will read on...
-==Another Example, Followed by Explanation==
+Tbz143 Appreciate you sharing, great post.Thanks Again. Keep writing.
-Now let's try something a bit more complicated:
- <nowiki>str left = "Hello"
-str right = "world!"
-−
-print left + " " + right</nowiki>
-−
-Now, recompile the script and pull the lever to make sure its still working; it should have printed the exact same thing to the console.  The difference is, we separated the string into three parts using two ''variables'' (''left'' and ''right'') of type ''str'', and one ''str literal'' (" "), then stuck them together with the '+' operator.
-−
-===Order of Execution===
-In many programming languages (Spellscript included), statements are executed from top to bottom-- in programmer jargon, this means that Spellscript is an ''imperative'' programming language.  To elaborate on the above example: first, ''left'' is given the value ''"Hello"'', then ''right'' is given the value ''"world!"'', and then finally, the variables are combined and the result is printed to the console.
-−
-If the top two lines of code were placed ''below'' the print statement, the script would have failed to compile!  This is because variables must be ''declared'' before they are used (which ''left'' and ''right'' wouldn't be.)  Thus, order of statements is extremely important, and is one of the first hurdles for novice programmers to understand.  While in this example the script simply fails to compile, other cases may result in a valid but logically different result.
-−
-===Variables and State===
-Next on the explanation agenda are ''variables'', a very important concept in programming-- they allow your scripts to have "state".  In other words, the value stored in a variable can change (hence the name), which can in turn affect the execution of your script.
-−
-A variable is declared like ''<type> <name>'', and its valued is changed with the assignment operator, ''='', like so:
- <nowiki>str left
-left = "Hello"
-−
-int number
-number = 3</nowiki>
-The two may be combined, as in the original script, to both declare and assign to the variable in one statement:
- <nowiki>int anotherNumber = 200</nowiki>
-Here's a simple example to demonstrate how a variable can change:
- <nowiki>int number = 0
-print number
-−
-number = 7
-print number
-−
-number = 234
-print number</nowiki>
-If put in a Spellscript-block, the above would have printed "0", "7" and then "234" to the console.
-−
-====Undefined Behavior====
-Currently in Spellscript, using a declared variable before anything is assigned to it results in "undefined behavior."  This means nothing is guaranteed about that variable's value; it could be some random value, or something that will crash your script when accessed.  While some day Spellscript will validate this and throw a compilation error, it's currently your responsibility to ''always'' assign to your variables before using them.  Using compound declaration-assignment statements instead of plain ol' declaration statements is a surefire way to avoid this issue.
 ==The ''If'' Statement==

@@ Line 4: / Line 4: @@
 See [[Spellscript]] for a general language reference-- otherwise, read on...
-==Your First Spellscript Script==
+ZKp5sE Great, thanks for sharing this article post.Thanks Again. Will read on...
-Go ahead and start Minecraft ''with the console open'' ([[Viewing Spellscript Output|instructions]]), then create a new single player world in Creative Mode.  Now, place a Spellscript-Block wherever you please and a lever right next to it--you can find both in the Creative inventory.  Once those are placed, open up the Spellscript Editor by right-clicking on the block.  By default, it's name will be "Untitled Spellscript-Block", and it's content will be "pass" (a statement which equates to "Do nothing").  For your first script, we're going to print "Hello world!" to the command line!  Simply replace "pass" with the following:
- <nowiki>print "Hello world!"</nowiki>
-−
-Now press ''ctrl''+''enter'', and verify the script is compiling.  Now press ''escape'', pull the lever, and voila!  Was "Hello world!" printed to your console?  Great, you've created your first Spellscript script!  Easy peasy.  This is called a "print" statement, and simply prints the expression to its right to the terminal.
 ==Another Example, Followed by Explanation==