Headcannon Game Engine Game Creation - Keywords and Expressions

Keywords and Expressions

Introduction

Variable Type Overrides

Available Keywords

Eval

Else

EndIf

While

Forever

BreakDo

IfFlag

Flag

Array

TableB/TableW/TableD

Combined Example

Introduction

Keywords can be used in place of certain Commands within

Functions

Variable Type Overrides

These "overrides" are not generally necessary, as

Alias Names

When numeric variable IDs are used anywhere within the string instead of Alias Names- The numeric ID provides no other context by which to determine its intended use
When an Alias Name is used to represent the ID of its corresponding variable, instead of obtaining the contents of that variable- The use of an Alias Name otherwise implies that the operation should use the value stored within the variable that it references, not the ID number of the variable itself

Type		Meaning
R		Identifies the variable as a "Game Variable"/"Register"
P		Identifies the variable as a "Player Variable"
O		Identifies the variable as an "Object Variable"
C		Identifies the value as a "Constant Value" (an explicit number value)

Available Keywords

The following is a list of available Keywords and their uses:

Eval

Short for "Evaluate", this Keyword signifies that the following string is a Math Expression. This Keyword can be used for writing expressions containing one, two, or three variables in the following formats (using example

Variable Alias Names and Constant Values

~Eval  _TempReg  = _Player_X_Pos + 160
~Eval  _TempReg  = 32
~Eval  _TempReg += _Object_X_Pos
~Eval  _TempReg++
~Eval -_TempReg

~Eval(RPC) U_TempReg  = A_Player_X_Pos + 160
~Eval(RC)  U_TempReg  = 32
~Eval(RO)  U_TempReg += _Object_X_Pos
~Eval(R)   U_TempReg++

Remember that standard Player Fetching and Object Fetching rules apply when using Player and/or Object Variables.

Operator		Meaning
=		Assignment- The result of the operation on the right will be placed into the variable on the left
+		Addition- The values to the left and right of this operator are added together
-		Subtraction- The value to the right of this operator is subtracted from the value to the left of this operator
*		Multiplication- The values to the left and right of this operator are multiplied together
/		Division- The value to the left of this operator is divided by the value to the right of this operator
<<		Arithmetic Left Shift- The bits of the value to the left of this operator are shifted left the number of times described by the value to the right of this operator. This is a signed operation
>>		Arithmetic Right Shift- The bits of the value to the left of this operator are shifted right the number of times described by the value to the right of this operator. This is a signed operation
&		Logical AND- The value to the left of this operator is ANDed by the value to the right of this operator
\|		Logical OR- The value to the left of this operator is ORed by the value to the right of this operator
^		Logical XOR- The value to the left of this operator is XORed by the value to the right of this operator
%		Modulus- The result of this operation is the remainder of division of the value to the left of this operator by the value to the right of this operator
POW		Raise to Power- The value of the variable to the left of this operator is raised to the power of the value of the variable to the right of this operator
+=		Addition Assignment- The value of the variable to the left of this operator is increased by the value to the right of this operator
-=		Subtraction Assignment- The value of the variable to the left of this operator is increased by the value to the right of this operator
*=		Multiplication Assignment- The value of the variable to the left of this operator is multiplied by the value to the right of this operator
/=		Division Assignment- The value of the variable to the left of this operator is divided by the value to the right of this operator
<<=		Arithmetic Left Shift Assignment- The bits of the value of the variable to the left of this operator are shifted left the number of times described by the value to the right of this operator. This is a signed operation
>>=		Arithmetic Right Shift Assignment- The bits of the value of the variable to the left of this operator are shifted right the number of times described by the value to the right of this operator. This is a signed operation
&=		Logical AND Assignment- The value of the variable to the left of this operator is ANDed by the value to the right of this operator
\|=		Lorical OR Assignment- The value of the variable to the left of this operator is ORed by the value to the right of this operator
^=		Logical XOR Assignment- The value of the variable to the left of this operator is XORed by the value to the right of this operator
%=		Modulus Assignment- The value of the variable to the left of this operator is made equal to the remainder of division of itself by the value to the right of this operator
POW=		Raise to Power Assignment- The value of the variable to the left of this operator is raised to the power of the value of the variable to the right of this operator
++		Increment- The value of the variable to the left of this operator is increased by 1
--		Decrement- The value of the variable to the left of this operator is decreased by 1

Special cases

Absolute Value

~Eval  _TempReg = +_OtherReg ;Find the absolute value of "OtherReg" and store it in "TempReg"
~Eval +_TempReg              ;Convert the value of "TempReg" to its absolute value

Negate

~Eval  _TempReg = -_OtherReg ;Store the negation of the value of "OtherReg" into "TempReg"
~Eval -_TempReg              ;Directly negate the value of "TempReg"

This Keyword signifies that the following expression is an

"If" Conditional

Variable Alias Names and Constant Values

~If _TempReg <= 512

~If(RC) U_TempReg <= 512

Remember that standard Player Fetching and Object Fetching rules apply when using Player and/or Object Variables.

Operator		Meaning
<		Less Than- This condition is considered true if the value to the left of this operator is less than the value to the right of this operator
>		Greater Than- This condition is considered true if the value to the left of this operator is greater than the value to the right of this operator
<=		Less Than or Equal To- This condition is considered true if the value to the left of this operator is either less than or equal to the value to the right of this operator
>=		Greater Than or Equal To- This condition is considered true if the value to the left of this operator is greater less than or equal to the value to the right of this operator
==		Equal To- This condition is considered true if the values to the left and right of this operator are equal
!=		Not Equal To- This condition is considered true if the values to the left and right of this operator are not equal

Else

This Keyword functions the same as the "

_Else

If Block

~Else

EndIf

This Keyword functions the same as the "

_EndIf

If Block

~EndIf

This Keyword functions the same as the "

_Do

~Do

While

This keyword signifies that the following expression is the condition that must be satisfied for the preceding code, back to the corresponding

Variable Alias Names and Constant Values

~While _TempReg <= 512

~While(RC) U_TempReg <= 512

Remember that standard Player Fetching and Object Fetching rules apply when using Player and/or Object Variables.

Operator		Meaning
<		Less Than- This condition is considered true if the value to the left of this operator is less than the value to the right of this operator
>		Greater Than- This condition is considered true if the value to the left of this operator is greater than the value to the right of this operator
<=		Less Than or Equal To- This condition is considered true if the value to the left of this operator is either less than or equal to the value to the right of this operator
>=		Greater Than or Equal To- This condition is considered true if the value to the left of this operator is greater less than or equal to the value to the right of this operator
==		Equal To- This condition is considered true if the values to the left and right of this operator are equal
!=		Not Equal To- This condition is considered true if the values to the left and right of this operator are not equal

Forever

This Keyword functions the same as the "

_Forever

~Forever

BreakDo

This Keyword functions the same as the "

_BreakDo

While

Forever

~BreakDo

IfFlag

This Keyword signifies that the following expression is an

"If" Conditional test

"Flag"

Variable Alias Names and Constant Values

~IfFlag _Bits[0]      == _On
~IfFlag _Bits[_RegID] == _Off

~IfFlag(RC) U_Bits[0]       == _On
~IfFlag(RR) U_Bits[U_RegID] == _Off

Remember that standard Player Fetching and Object Fetching rules apply when using Player and/or Object Variables.

Flag

This Keyword is used to set, unset, and flip

"Flag"

Variable Alias Names and Constant Values

~Flag _Bits[2]      = _On
~Flag _Bits[_RegID] = _Off
~Flag _Bits[1]      = _Flip

~Flag(RC) U_Bits[2]       = _On
~Flag(RR) U_Bits[U_RegID] = _Off
~Flag(RC) U_Bits[1]       = _Flip

Remember that standard Player Fetching and Object Fetching rules apply when using Player and/or Object Variables.

Array

This Keyword is used to set and retrieve values stored within an

"Array"

Variable Alias Names and Constant Values

~Array _ArrayStart[_IndexCtr] = 5
~Array _ArrayStart[_IndexCtr] = _TempReg

~Array _TempReg = _ArrayStart[_IndexCtr]

~Array(RRC) U_ArrayStart[U_IndexCtr] = 5
~Array(RRR) U_ArrayStart[U_IndexCtr] = U_TempReg

~Array(RRR) U_TempReg = U_ArrayStart[U_IndexCtr]

Remember that standard Player Fetching and Object Fetching rules apply when using Player and/or Object Variables.

TableB/TableW/TableD

These Keywords are used to retrieve values loaded into a

"Table"

Variable Alias Names and Constant Values

~Table _TempReg =        5[_IndexCtr]
~Table _TempReg =       Z1[_IndexCtr]
~Table _TempReg = _TableID[_IndexCtr]

~Table(RCR) U_TempReg =         5[U_IndexCtr]
~Table(RCR) U_TempReg =        Z1[U_IndexCtr]
~Table(RRR) U_TempReg = U_TableID[U_IndexCtr]

Remember that standard Player Fetching and Object Fetching rules apply when using Player and/or Object Variables.

Combined Example


;===================================================================================
;=====================
;Function 0 - Example=
;=====================

	;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
	;The code within this Function does nothing particularly useful, and only serves
	;to illustrate proper formatting for usage of each of the available Keywords.
	;
	;Assume that the following Alias Names have already been defined globally:
	;
	; Bits      (Game Register, Player Variable, or Object Variable)
	; Flop      (Constant ID value representing an index from 0-31 within a bitfield)
	; That      (Game Register, Player Variable, or Object Variable)
	; Values    (Game Register, Player Variable, or Object Variable, which marks the
	;            beginning of a series of variables to be used as an array)
	; SomeTable (Constant ID value representing one of several loaded "Tables"
	;
	;The following Alias names are HCGE Standard (although their file must be loaded):
	;
	; On        (1)
	; Flip      (2)
	;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

	.Alias Counter						;Create a local Alias Name "Counter" and auto-associate it with a reserved-space Register variable
								;Will be used as a loop counter
	.Alias Temp						;Create a local Alias Name "Temp" and auto-associate it with a reserved-space Register variable
								;Will be used as a temporary value holder
	.Alias ID						;Create a local Alias Name "ID" and auto-associate it with a reserved-space Register variable
								;Will be used as an Array/Table entry index number

	~IfFlag _Bits[_Flop] == _On				;If the bit at position "Flop" within the bitfield "Bits" is "On" (1), process the code between this Keyword and its corresponding "EndIf"

		~Eval _Counter = 0				;Ensure that the value stored in "Counter" starts at 0

		~Do						;This code will be processed at least once. The next "While" will loop back to here if its condition is satisfied

			~Eval _ID           = _That & $FC	;Perform a logical AND operation on the value of "That", and store the result in "ID"

			~Array _Temp        = _Values[_ID]	;From within the array "Values", take the value of the element at position "ID" and place it into "Temp"
			~Eval  _Temp       -= 4			;Subtract 4 from the value stored in "Temp"
			~Array _Values[_ID] = _Temp		;Place the current value of "Temp" into the array "Values" at the position of element "ID"

			~If _Temp == 0				;If the value stored in "Temp" is 0, process the code between this Keyword and the following "Else"

				~BreakDo			;The value stored in "Temp" is 0. "Break" (exit) this "Do" loop and immediately jump to the code imediately following "While _Counter < 8"

			~Else					;If the value stored in "Temp is not 0, process the code between this Keyword and the following "EndIf"

				~TableB _That = _SomeTable[_ID]	;Retrieve the value of the element at BYTE position "ID" within the table "SomeTable", and place it into "That"

			~EndIf					;This is the end of the "If _Temp == 0" condition

			~Eval _Counter++			;Increase the value stored in "Counter" by 1

		~While _Counter < 8				;Repeat the enclosed code if the value of "Counter" is less than 8

		;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
		;Function Processing continues here if the "While" condition becomes untrue, or if the "BreakDo" is processed
		;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

	~EndIf							;This is the end of the "IfFlag _Bits[_Flop] == _On" condition

	~Flag _Bits[_Flop] = _Flip				;Reverse the value of the bit at position "Flop" within the bitfield "Bits"

#End								;Mark the end of this Function