Manual:Using Variables in Mudlet - Revision history

Zooka: /* Variable Interpolation - the f function */

2024-08-04T11:22:08Z

Variable Interpolation - the f function

Zooka: /* Using Variables in Mudlet */

2024-08-04T11:13:13Z

Using Variables in Mudlet

Eraene: /* Saving via table.save & table.load */

2022-04-23T17:59:23Z

Saving via table.save & table.load

Vadi: Clarify what a "string" is

2021-08-16T09:02:45Z

Clarify what a "string" is

Kebap: /* Saving via table.save & table.load */ mention file name explicitly

2021-05-18T11:34:37Z

Saving via table.save & table.load: mention file name explicitly

Demonnic: /* Using Variables in Mudlet */

2021-03-13T18:32:35Z

Using Variables in Mudlet

Demonnic: /* Using Variables in Mudlet */

2021-03-13T17:44:43Z

Using Variables in Mudlet

Demonnic: /* Using Variables in Mudlet */

2021-03-13T17:02:21Z

Using Variables in Mudlet

Kebap: add description text for page

2021-01-05T10:47:49Z

add description text for page

Kebap: /* Saving via table.save & table.load */ typo fix of 2013 didn't fix all occurrences

2020-11-23T14:38:34Z

Saving via table.save & table.load: typo fix of 2013 didn't fix all occurrences

@@ Line 40: / Line 40: @@
 Note: You can't use a + b to concatenate string values. For this you must use the double-dot: <code>..</code>
-== Variable Interpolation - the <code>f</code> function ==
+== String Interpolation - the <code>f</code> function ==
 However, starting with Mudlet 4.11.0 we have included the f function to perform string interpolation. This is a very fancy way of saying "replacing code in strings with their value". When you run a string through the f function then it replaces anything inside a pair of {} with the value of the variable or outcome of the expression. To expand upon the example above:
@@ Line 83: / Line 83: @@
 end
 </syntaxhighlight>
 == Tables as Lists ==

@@ Line 39: / Line 39: @@
 </syntaxhighlight>
 Note: You can't use a + b to concatenate string values. For this you must use the double-dot: <code>..</code>
 However, starting with Mudlet 4.11.0 we have included the f function to perform string interpolation. This is a very fancy way of saying "replacing code in strings with their value". When you run a string through the f function then it replaces anything inside a pair of {} with the value of the variable or outcome of the expression. To expand upon the example above:
@@ Line 81: / Line 83: @@
 end
 </syntaxhighlight>
 There is another form of variables in Lua called tables which can be used for lists, arrays or dictionaries. This is explained later. For an in-depth coverage of variables in Lua take a look at a Lua tutorial e. g. this one on numbers http://Lua-users.org/wiki/NumbersTutorial and this one on strings http://Lua-users.org/wiki/StringsTutorial or this one on Lua tables http://Lua-users.org/wiki/TablesTutorial
@@ Line 100: / Line 105: @@
 </syntaxhighlight>
 In Lua all undefined variables are initialized to the value nil. The value nil is not the same thing as the number 0 or the empty string "". What it means is that a variable that has the value nil has not been declared yet and does not exist. If a variable does not exist, it cannot be used as its value is undefined at this point. Consequently, increasing the value of nil by one is impossible as the variable doesn’t exist yet and will lead to a Lua error. The above script simply checks if the variable myKills has been defined yet and if it hasn’t, it will declare the variable and set its value to 0.
-=== Tables as Lists ===
 Having variables that hold a single value is the most important usage of variables, but very often you’ll like to define variables that hold a list of values e. g. a list of your enemies, a list the items you are currently carrying etc.. To define a variable to be a list you need to declare it to be a Lua table. Let’s declare the variable myEnemies as a list containing the names of your enemies:
 <syntaxhighlight lang="lua">
@@ Line 127: / Line 132: @@
 To remove an item from the list, you can use the function <code>table.remove( listName, item index )</code>.
-=== Saving variables ===
+== Saving variables ==
 You might notice that Mudlet doesn't save your variables between profiles restarts. The reasons for this are technical, but all it means is that you have flexibility in how to deal with them. There are several ways, so the most common and easiest ones will be explained here.

@@ Line 160: / Line 160: @@
+}
-local location = getMudletHomeDir() .. "/mychar"
+local location = getMudletHomeDir() .. "/mychar.lua"
 table.save(location, mychar)
 -- sample echo to show where the file went:
@@ Line 170: / Line 170: @@
 <syntaxhighlight lang="lua">
 mychar = mychar or {}
-table.load(getMudletHomeDir() .. "/mychar", mychar)
+table.load(getMudletHomeDir() .. "/mychar.lua", mychar)
 display(mychar)
 echo(f"My name is: {tostring(mychar.name)}")

@@ Line 25: / Line 25: @@
 </syntaxhighlight>
-Lua variables can be either a string or a number. They are whatever there were initially initialized with or what data type they can be converted to.
+Lua variables can be either a string of letters (aka <code>string</code>) or a <code>number</code>, among a few others. They are whatever there were initially created with or what data type they can be converted to.
 <syntaxhighlight lang="lua">
 a = "Jim"
@@ Line 38: / Line 38: @@
 e = a .. c -- and e will equal "Jim350"
 </syntaxhighlight>
-Note: You can't use a + b to concatenate string values. For this you must use the double-dot: ..
+Note: You can't use a + b to concatenate string values. For this you must use the double-dot: <code>..</code>
 However, starting with Mudlet 4.11.0 we have included the f function to perform string interpolation. This is a very fancy way of saying "replacing code in strings with their value". When you run a string through the f function then it replaces anything inside a pair of {} with the value of the variable or outcome of the expression. To expand upon the example above:

@@ Line 151: / Line 151: @@
 Next, enter a more proper solution. This'll actually save the variables to a file and load them from it - so if you change the variable values, the current ones will be saved, and will be loaded next time properly. This method works with a table containing your variables though, not individual variables themselves - see [http://lua-users.org/wiki/TablesTutorial Lua tables tutorial] on how to create and use those.
-<code>table.save(where to save, what table to save)</code> takes the location of a file to save variables to, and a table containing your variables to save. Location can be anywhere on your computer, but a good default place is your profile folder, whose location can be obtained with getMudletHomeDir().
+<code>table.save(where to save, what table to save)</code> takes the location and name of a file to save variables to, and a table containing your variables to save. Location can be anywhere on your computer, but a good default place is your profile folder, whose location can be obtained with getMudletHomeDir().
 <syntaxhighlight lang="lua">
@@ Line 166: / Line 166: @@
 </syntaxhighlight>
-<code>table.load(where to load from, what table to use)</code> is similar - it takes the location of the file to load, and a table name to use for the loaded variables.
+<code>table.load(where to load from, what table to use)</code> is similar - it takes the location and name of the file to load, and a table name to use for the loaded variables.
 <syntaxhighlight lang="lua">

@@ Line 117: / Line 117: @@
 <syntaxhighlight lang="lua">
 table.insert( myEnemies, matches[2] )
-echo( "Added a new enemy:" .. matches[2] .. "\n" )
+echo( f"Added a new enemy:{ matches[2] }\n" )
 </syntaxhighlight>
 Save the alias by clicking on "Save Item" and try it out by entering into the Mudlet's command input line. Aliases are explained in further detail below.
@@ Line 163: / Line 163: @@
 table.save(location, mychar)
 -- sample echo to show where the file went:
-echo(string.format("Variables saved in: '%s'", location))
+echo(f"Variables saved in: '{location}'")
 </syntaxhighlight>
@@ Line 172: / Line 172: @@
 table.load(getMudletHomeDir() .. "/mychar", mychar)
 display(mychar)
-echo("My name is: ".. tostring(mychar.name))
+echo(f"My name is: {tostring(mychar.name)}")
 </syntaxhighlight>

← Older revision		Revision as of 17:44, 13 March 2021
Line 61:		Line 61:

	A shrewd observer might notice that I have written the above uses of f without the usual parentheses. In Lua you can omit the () when you are only passing a single string argument to the function. It is usually considered best practice to include the () but in the case of f for interpolation I find it reads a bit better without them. As shown in the example above it works with or without them in place.		A shrewd observer might notice that I have written the above uses of f without the usual parentheses. In Lua you can omit the () when you are only passing a single string argument to the function. It is usually considered best practice to include the () but in the case of f for interpolation I find it reads a bit better without them. As shown in the example above it works with or without them in place.
		+
		+	For a more 'real world' example and comparison of concatenation, f, and string.format consider the following:
		+	<syntaxhighlight lang="lua">
		+	-- For the following, we assume the following variables exist:
		+	-- target which holds the target's name
		+	-- target_health_color which is a cecho color determined elsewhere
		+	-- target_health which is the actual health the target has.
		+
		+	-- this function uses the concatenation operator .. to glue strings together for display
		+	function displayTarget()
		+	local msg = "\n<green>Target:<r> " .. target .. " <green>Health:<r> " .. target_health_color .. target_health
		+	cecho(msg)
		+	end
		+
		+	-- this function does the same thing, but uses f
		+	function displayTarget()
		+	local msg = f"\n<green>Target:<r> {target} <green>Health:<r> {target_health_color}{target_health}"
		+	cecho(msg)
		+	end
		+	</syntaxhighlight>

	There is another form of variables in Lua called tables which can be used for lists, arrays or dictionaries. This is explained later. For an in-depth coverage of variables in Lua take a look at a Lua tutorial e. g. this one on numbers http://Lua-users.org/wiki/NumbersTutorial and this one on strings http://Lua-users.org/wiki/StringsTutorial or this one on Lua tables http://Lua-users.org/wiki/TablesTutorial		There is another form of variables in Lua called tables which can be used for lists, arrays or dictionaries. This is explained later. For an in-depth coverage of variables in Lua take a look at a Lua tutorial e. g. this one on numbers http://Lua-users.org/wiki/NumbersTutorial and this one on strings http://Lua-users.org/wiki/StringsTutorial or this one on Lua tables http://Lua-users.org/wiki/TablesTutorial

@@ Line 34: / Line 34: @@
 --Then you can write:
-e = c + d and e will equal 351
+e = c + d -- and e will equal 351
-e = a .. b and e will equal "JimTom"
+e = a .. b -- and e will equal "JimTom"
-e = a .. c and e will equal "Jim350"
+e = a .. c -- and e will equal "Jim350"
 </syntaxhighlight>
 Note: You can't use a + b to concatenate string values. For this you must use the double-dot: ..
 There is another form of variables in Lua called tables which can be used for lists, arrays or dictionaries. This is explained later. For an in-depth coverage of variables in Lua take a look at a Lua tutorial e. g. this one on numbers http://Lua-users.org/wiki/NumbersTutorial and this one on strings http://Lua-users.org/wiki/StringsTutorial or this one on Lua tables http://Lua-users.org/wiki/TablesTutorial

← Older revision		Revision as of 10:47, 5 January 2021
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	{{TOC right}}		{{TOC right}}
		+	{{#description2:Manual on variables, how to use one, how to use many, how to save them for next session, etc.}}
	=Using Variables in Mudlet=		=Using Variables in Mudlet=