el microScript cheatsheet

microScript cheatsheet

This is a cheatsheet for microScript 2.0

Variables

local

f = function()
  local count = 0
  while count < 100
    (...)
  end
end // visibility of the local variable stops here, when the "block" where it was created ends

Tip:

• use local variables for temporary values in functions
• Avoid mixing local and global variables with the same name

global

score = 0
level = 1

object

Variables, set during the course of an object method call, are made properties of the current object:

player = object
  position_x = 0
  position_y = 0
  setPosition = function(x,y)
    position_x = x // sets player.position_x
    position_y = y // sets player.position_y
  end
end

This is shown above on a plain object, but also applies to class instances

Global variables can still be changed from an object's method by using the prefix global.

player = object
  update = function()
    global.score += 1
  end
end

checking type

myvar.type

myobject.some_property.type

delete properties

delete myobject.some_property
delete this.something
delete some_variable
delete myobject[getPropertyToDelete()]

values

myvar.type == 0	myvar is not defined
myvar.type == "number"	myvar is a number
myvar.type == "string"	myvar is a string
myvar.type == "function"	myvar is a function
myvar.type == "list"	myvar is a list
myvar.type == "object"	myvar is an object

Numbers

formatting

a = 1
b = 1.2
c = -4.5e-5    // = -4.5*10^(-5)

hexadecimal

h = 0x7FFF

conversion

Number.parse( string )	Parses a string and returns a number
num_variable.toString()	Returns the string representation of a number

operations

a + b	a - b	a * b	a / b
a ^ b	a to the exponent of b
a % b	remainder
a & b	binary and
a | b	binary or
a += b	a -= b	a *= b	a /= b
a %= b	a &= b	a |= b

Strings

delimiters

"double-quote delimited string"
'simple-quote delimited string'
"""triple double-quote delimited string"""

escaping

"\""	double quote
"\n"	line feed
"\\"	backslash
"double-quote: "" "	a pair of double-quotes is parsed as a single double-quote

operations

string1 + string2	Concatenates two strings
string.length	Length of the string
string.substring( i1, i2)	Returns a substring of the character string, starting at index i1 and ending at index i2
string.startsWith( s )	Returns whether string starts exactly with s
string.endsWith( s )	Returns whether string ends exactly with s
string.indexOf( s )	Index of the first occurrence of s in string, or -1
string.lastIndexOf(s)	Index of the last occurrence of s in string, or -1
string.replace(s1,s2)	Returns a new string with s1 replaced by s2
string.toUpperCase()	Returns the string converted to upper case
string.toLowerCase()	Returns the string converted to lower case
string.split(s)	Divides the string into a list of substrings, using the separator provided
string.charAt( position )	Returns the character at the given position
string.charCodeAt( position )	Returns the UTF-16 character code at given position
string.concat( str2 )	Returns string + str2
string.trim()	Returns string with leading and trailing space characters removed (space, tabs, LF)
string.trimEnd()	Returns string with trailing space characters removed (space, tabs, LF)
string.trimStart()	Returns string with leading space characters removed (space, tabs, LF)
String.fromCharCode( code )	Returns the character of the given code, as a string

Lists

operations

list = []	Empty list
list.length	Length of the list
list.push( element )	Adds the element to the end of the list
list.pop()	Removes the last element from the list and returns it (or 0 if empty)
list += element	Same
list.insert( element )	Inserts an element at the beginning of the list
list.insertAt( element, index)	Inserts an element at the given index in the list
list.indexOf( element )	Returns the position of the element in the list else -1
list.contains( element )	Returns 1 when element is in the list else 0
list.removeAt( index )	Removes from the list the element at position index
list.removeElement( element )	Removes from the list element, if it can be found in the list
list1.concat( list2 )	Returns a new list obtained by appending list2 to list1
list1 += list2	Same
list3 = list1 + list2	list3 becomes the concatenation of list1 and list2
list.sortList( func )	sorts the list using the comparison function passed

Objects

create

obj = object
  x = 1
  y = 2
end

properties

obj.x = 2
obj["y"] = obj.x + 3

object methods

obj.incrementX = function() x += 1 end
obj.incrementX()

Functions

definition

add = function( x, y )
  return x+y
end

invocation

five = add( 2, 3 )

default args

display = function( text="placeholder text" )
  print(text)
end

display("My text")
display()

implicit returns

square = function(x) x*x end

Loops

for loop

for i=1 to 10
  print(i)
end

for i=10 to 0 by -1
  print("countdown: "+i)
end


// Iterate over elements in a list

list = [1,2,3,4,5]
for element in list
  print(element)
end


// Iterate over properties of an object

obj = object
  x = 1
  y = 2
  z = 3
end

for prop in obj
  print(prop + " = " + obj[prop])
end

while loop

count = 0
while count < 1000
  print(count)
  count += 1
end

Conditional statements

if x == 1 then
  print("one")
elsif x == 2 then
  print("two")
elsif x > 2 then
  print("more")
else
  print("less than one")
end

// conditionals are expressions and also return a value

sign_x = if x >= 0 then "positive" else "negative" end

Random

// random number in the rangle [0 .. 1]
random.next()

// random integer in the range [0 .. 99]
random.nextInt(100)

// reseed the random number generator
random.seed(1234)

// clone the random number generator
r = random.clone()

// reseeded clone of a random number generator
r = random.clone(1234)

// use the clone as the original random object
r.next()

Schedule

after

after 5 seconds do
  backToMainMenu()
end

every

every 200 milliseconds do
  score += 100
end

do

do     // the code enclosed will be executed in a new separate thread
  for i=1 to 100000000
    doHeavyWork(i)
  end
end

sleep

sleep 1 second

sleep 200 milliseconds

sleep 200 // if unspecified, it is milliseconds by default

Threads

after, every and do all return a thread value:

thread = every 1000 do print(counter += 1) end

thread.pause()

thread.resume()

thread.stop()

list secondary threads

for t in system.threads
  t.pause()
end

Predefined

predefined functions

round( x )	sin( x )	sind( x )	sqrt( x )	min( x, y )
floor( x )	cos( x )	cosd( x )	log( x )	max( x, y )
ceil( x )	tan( x )	tand( x )	exp( x )
abs( x )	acos( x )	asind( x )	pow( x, y )
	asin( x )	acosd( x )
	atan( x )	atand( x )
	atan2( y, x )	atan2d( y, x )

predefined constants

constant	value
PI	Number Pi
true	Predefined to 1
false	Predefined to 0

Classes

definition

MyClass = class extends MyParentClass
  constructor = function( x, y, size )
    super( x, y )
    this.size = size
  end

  getSize = function()
    return size
  end
end

use

my_object = new MyClass( 10, 12, 20 )
print( my_object.getSize() )

Comments

// this is a line comment
x = 1 // this is a line end comment

/* This is
  a block
  comment
  */

// below is an inline comment
if /*true*/ false then doSomething() end