MultiCharts | PowerLanguage Tutorials | CH4: Branch

Branch

The if-else and switch branch syntax allows the program to decide the direction of execution. If specific conditions are met, specified instructions are executed, otherwise other instructions are executed.

There are two steps here:
The first step: Use and, or, etc. logical operators compose a logical expression for the conditions to be satisfied.
The second step: Combine the logical expression with the if-else and switch syntax to determine the direction to be executed.

Logical Operator

Following is logical operators provided by PowerLanguage to form logical statements.

邏輯運算子意義
andand
oror
notnot
>greater than
<less then
>=greater equal or equal to
<=less then or equal to
=equal to
<>not equal to
cross above/cross overcross above same as cross over, interchangeable
cross below/cross undercross below same as cross under, interchangeable

Except for cross above and cross below, other logical operators have the same meaning as mathematical logic.

A cross above B is defined as follows:

  • At the current bar, the value of A is greater than the value of B and at the previous bar, the value of A is less than the value of B.
  • At the current bar, the value of A is greater than the value of B but at the previous one or more bars, the value of A is equal to the value of B, then before these equals, the value of A is less than the value of B.

A cross below B is defined as follows:

  • At the current bar, the value of A is less than the value of B and at the previous bar, the value of A is greater than the value of B.
  • At the current bar, the value of A is less than the value of B but at the previous one or more bars, the value of A is equal to the value of B, then before these equals, the value of A is greater than the value of B.

Logical Expression

A logical statement is a statement that returns a TrueFalse value.
E.g:
5<3: It is a logical statement, 5 is less than 3, which returns false.
8<>9: It is a logical statement, 8 is not equal to 9, which returns true.
8<>9 and 5<3: It is a logical statement, 8 is not equal to 9 and 5 is less than 3, which returns false.

if-else

if-else allows the program to choose which way to execute based on the result of the logical expression.
If the result of the logical expression is true, execute the True_Instruction, and if it is false, execute False_Instruction.

There are two kinds of if-else syntax: single-line instruction syntax and multi-line instruction syntax.

Single-line instruction syntax

True_Instruction or False_Instruction can only have one line and no need begin/end.
[] indicates the else instructions can be deleted if it is not needed.

if Logical_Expression then True_Instruction 
[else False_Instruction];

Multi-line instruction syntax

True_Instruction or False_Instruction can be one line or multiple lines and they must be wrapped with begin/end.
[] indicates the else instructions can be deleted if it is not needed.
The last end requires a semicolon, and the rest of the end do not need a semicolon.

if Logical_Expression then begin 
  True_Instruction_1;
  True_Instruction_2;
  ...
end
[else begin
  False_Instruction_1;
  False_Instruction_2;
  ...
end];

else if syntax

In addition to the two-way usage, if-else can also be used in combination with else if as multi-way usage to judge multiple logical statements and decide which way to execute.
[] indicates the else instructions can be deleted if it is not needed.
The last end requires a semicolon, and the rest of the end do not need a semicolon.

if Logical_Expression_1 then begin 
  True_Instruction_1;
  ...
end
else if Logical_Expression_2 then begin
  True_Instruction_2;
  ...
end
.
.
.
else if Logical_Expression_N then begin
  True_Instruction_N;
  ...
end
[else begin
  Instruction_For_All_False;
  ...
end];

Example

If UpTrend = False Then Sell Next Bar Market;
If UpTrend = True Then Begin
  Buy Next Bar Market;
End
Else Begin
   SellShort Next Bar Market;
End;
Variables:
	EMA(0);
EMA = XAverage(Close, 20);
if Close > EMA then begin
	Print("Close is above the EMA");
end else if (Close < EMA) then begin
	Print("Close is below the EMA");
end else 
	Print("Close is equal to the EMA");

switch

The switch determines the instruction to be executed by the return value of the Expression which ca be Numerical, String or TrueFalse type.

switch syntax

When the program executes to switch, the following actions are performed:

  1. Compare the returned value of Expression with each Case_Expression, and execute Case_Instructions if the conditions of Case_Expression are met.
  2. If all Case_Expressions do not meet, the program executes the Default_Instructions.
    [] indicates the default instructions can be deleted if it is not needed.

The PowerLanguage, unlike other programming languages, there is no need to add a break to jump to the end;.
The program jumps to the end; of switch after finish execution of the Case_Instructions.

switch ( Expression )
begin
    case Case_Expression:  Case_Instructions;
    [default: Default_Instructions;]
end;

Case_Expression

The type of Case_Expression must be as same as the type of the returned value of the Expression.

Case_Expression can be a single value, the multiple values, a range, or used with logical operators.

Example

The value of var1 is 8, which satisfies Case 4 to 8, so Print("if 4 to 8"); is executed.

var: var1(5+3);
Switch(var1) 
Begin
   Case 1, 2, 3: //the multiple values: 1, 2, 3
	Print("if 1, 2, 3");

   Case 4 to 8: //a range: 4 to 8
	Print("if 4 to 8");

   Case 9 to 15, 20: //9 to 15 or 20
	Print("if 9 to 10, 20");

   Case is > 40: //greater than 40，is is a skip word，can be omitted
	Print("if is > 40");

   Default:
	Print("if default");
End;

The value of str1 is "I", which satisfies Case "H", is >= "I", so print("if H, is >= I"); is executed.

var: str1("I");
Switch(str1) 
Begin
   Case "A", "B", "C": //the multiple values: A, B, C
	Print("if A or B or C");

   Case "D" to "G": //a range: D to G
	Print("if D to G");

   Case "H", is >= "I": //H or greater then I
	Print("if H, is >= I");

   Default:
	Print("if default");
End;

Reference

https://www.multicharts.com/trading-software/index.php?title=Category:Comparisons_and_Loops

https://www.multicharts.com/trading-software/index.php?title=Above

https://www.multicharts.com/trading-software/index.php?title=Below

https://www.multicharts.com/trading-software/index.php?title=If

https://www.multicharts.com/trading-software/index.php?title=Switch

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