Beginner's Guide to MultiCharts Programming

This article highlights some PowerLanguage formatting tips, as discussed in a forum topic <ref>MC Programing - What I’ve learned</ref>.

Layout

Some tips regarding the layout of a coding script.

General layout tips

Some general layout tips are:

• Use tabs and empty lines to make the code better readable - don't forget: if you want to edit your script a half-year from now, you'll still need to be able to comprehend it.
• Make use of comments.
• While it isn't needed in EasyLanguage to use parentheses ( & ) after an 'if' statement, it makes the code better readable and prevents errors.
• Make your code explicit. For example, instead of writing if LastBarOnChart then write if (LastBarOnChart = True) then. While both statements work, the latter makes it easier to debug and makes the implicit assumptions you're making explicit.

Description

It's considered good programming practice to include a description, changelog and dates into your script. This helps with keeping track of changes or reverting any made changes. An example of a good description is the following.

{
   Type - Indicator
   Name - NWT SPI Day Session
   Desc - Plot a ribbon show Green for the Day Session and Red for the Night Session
      Just to enable quicker back viewing of the data
          
   Version    Date          Reason
   1         17/12/2011   Start
}

Script Inputs

By including comments in the section of the script where the inputs and variables are defined the comprehension of the variables will be greater.

An example of poor formatting would be the following.

Inputs : High_MA_Len(10),Low_MA_Len(8),MedLen(8),PointSize(0.0001), StopLossSize(5), BreakEvenSize(7);

A better formatting, both cleaner and easier to understand, would be:

Inputs :    
  High_MA_Len(10), Low_MA_Len(8), // Moving average lengths
  MedLen(8),                      // Median Look back Length
  PointSize(0.0001);              // Actual Point size of the instrument

Other Input formatting suggestions

• Start IntraBarPersist variables with a captial letter (e.g. MyDefinedVariable) and start regular variables with a normal letter (e.g. myDefinedVariable). This helps to keep track of which variables are regular and which ones are IntraBarPersist.

If else statements

When writing If Else statements the use of tabs is highly recommended.

Some examples of poor formatting would be:

If UpTrend Then Begin
Buy Next Bar Market;
End
Else Begin
SellShort Next Bar Market;
End;

If UpTrend Then Buy Next Bar Market
Else SellShort Next Bar Market;

If UpTrend Then Buy Next Bar Market Else SellShort Next Bar Market;

Better formatting would be:

if (UpTrend = True) then begin
   
      Buy Next Bar Market;
      Initial_Stop = Low[1];
   
else begin

      SellShort Next Bar Market;
      Initial_Stop = High[1];

end;

Closing of 'begin'... 'end' statements

A little tip for the closing of begin and end statements would be to include '//: ' after the end statement followed by a description of the if statement. This makes it relatively easy in debugging to see what the code block the 'end;' statement closes.

For example:

if (MarketPosition(0) = 0) then begin

   if (CurrentContracts < posSize) then begin
   
      if (enterLong = True) then
         Buy ("EL Limit") posSize contracts next bar at ELPrice limit;
         
      if (enterShort = True) then
         SellShort ("ES Limit") posSize contracts next bar at ESPrice limit;
         
   end; //: CurrentContracts < PosSize

end; //: No MarketPosition Intrabar

References

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