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Mystic Programming Language

General Notes About Using The MPL

The syntax of the Mystic BBS Programming Language follows closely to that of the Turbo Pascal series of programming compilers. At one time, the language was almost 100% Turbo Pascal compatible (except for the BBS functions) but it has been slightly changed to make it a little more friendly to the programmer.

Two versions of the programming compiler are available in the scripts directory. The first one, MIDE.EXE, is a fully functional IDE for creating and compiling MPE programs. This program looks similar to the Turbo Pascal IDE, including syntax highlighting of all command keywords! The second version of the compiler is MPLC.EXE. This is a command line compiler supplied so you are not forced to use MIDE.EXE to write programs. If you do not find the MIDE interface to be satisfactory, then you can use your favorite text editor and MPLC.EXE to create programs!

The following are some quick notes about the syntax of the language as well as some notes about things that aren't working as they probably should be:

Comments

All text after a two slashes (⁄⁄) is considered a comment. It will be ignored until the next line of code. For example:

WriteLn ('Hello There')  ⁄⁄ This is a comment and will be ignored.

Operation types

The MPL does not follow the order of operations when doing mathmatical equations (ie PEMDAS - parenthesis, exponents, multiplication, division, addition, subtraction). So math functions are done in the order that they appear in the expression.

This doesn't mean its not POSSIBLE to do PEMDAS-ordered expressions, it will just take a little more effort on the programmer's behalf.

The following operation codes are supported for mathematical equations:

− Subtract
+ Addition
* Multiplication
⁄ Division
% Modulus Operator

Bitwise math

MPL fully supports bitwise math and operators! The following are implemented:

AND - Bitwise AND
OR  - Bitwise OR
XOR - Bitwise exclusive OR
SHL - Bitwise shift left
SHR - Bitwise shift right

Example:

Const
  UserDeleted = $00000004;  // Deleted bit from records.pas

Begin
  GetThisUser;

  If UserFlags AND UserDeleted <> 0 Then
    WriteLn('User is deleted');      
End;

Defining Variables

All variables are global to all of the program, including procedures. The syntax for declaring a variable follows:

Var <Variable Name> : <Variable Type>

Examples:

Var Dummy : Byte;
Var Str   : String;

Var
  Dummy1,
  Dummy2  : Byte;

The following variable types are supported:

Type            Format         Range
--------------- -------------- ----------------------------
Boolean         FALSE/TRUE     0..1
Char            Text           1 character
String          Text           Sequence of 1..255 characters
Byte            Numerical      0..255
Integer         Numerical      -32767..32767
Word            Numerical      0..65535
LongInt         Numerical      -2147483648..214748364
Cardinal        Numerical      0..4294967295
Real            Numerical      9.99

All variables except ARRAYs can be initialized when when defined:

Var TotalBases : LongInt = GetMBaseTotal(False)
Var Int        : Integer = 33
Var Str        : String = 'This is a string'

ARRAY multi-dimensional variables are supported. The syntax for declaring an array variable is:

Var <VarName> : ARRAY[<Low>..<High>] of <VarType>
Var <VarName> : ARRAY[<L>..<H>, <L>..<H>] of <VarType>
Var <VarName> : ARRAY[<L>..<H>, <L>..<H>, <L>..<H>] of <VarType>

Examples:

Var Dummy : Array[1..10] of Byte;
Var Str   : Array[5..10] of String;
Var Int   : Array[1..10, 1..10, 1..10] of Integer;

HEXIDECIMAL values are supported. They can be used in numeric variable assignment numerical evaluation, and in numeric constant variables. A hex value must begin with a $ character:

Const
  MyHexValue = $1F;

Value := $10;

If Value = $10 Then
  WriteLn('Value is 16 <in decimal>');

Record Structures

Groups data in to records. This command allows you to create a datatype of multiple different variable types. Defining the record:

Type
  testrec = record
  x : byte;
  y : byte;
  d : array[1..10,1..5] of string[9]
end

Declaring the record:

Var struct : testrec

Using the record:

struct.x:=1
struct.y:=10
struct.d[1,1]:='abc123'
WriteLn(struct.d[1,1]);
WriteLn('struct.x='+Int2Str(struct.x))

Code Blocks

When using multiple lines (more than one line) within a IF/ELSE/WHILE/CASE blocks, the lines need to be grouped into blocks between BEGIN and END statments. If there is only one line following the IF/ELSE/WHILE/CASE blocks, then no blocking statements are needed.

Examples:

If X = 1 Then 
  Begin
    WriteLn('X = '+Int2Str(X))
    X:=X+1
    WriteLn('X = '+Int2Str(X))
  End

The same is true for the ELSE block.

If X = 1 Then 
  Begin
    WriteLn('X = '+Int2Str(X))
    X:=X+1
    WriteLn('X = '+Int2Str(X))
  End 
Else 
  Begin
    WriteLn('X = '+Int2Str(X))
    X:=X-1
    WriteLn('X = '+Int2Str(X))
  End
  

FOR LOOPS

The syntax for a for loop is as follows:

For <variable> := <start number> <TO> or <DOWNTO> <end number> Do.
For A := 1 to 10 Do
  WriteLn (A)

For A := 10 DownTo 1 Do
  Begin
    WriteLn (A)
    WriteLn (A)
  End

REPEAT/UNTIL

The syntax for a repeat until loop is as follows:

Repeat
  <Code here>
Until <Boolean Expression>

IE:

Repeat
  WriteLn ('Blah blah')
Until A > 0 or A = 5

WHILE

The syntax for a while loop is as follows:

While <Boolean Expression> Do
  <Code Here>

IE:

While A > 0 and A = 5 Do
  WriteLn ('Blah')

OR:

While A > 0 and A = 5 Do
  Begin
    WriteLn ('Blah')
    WriteLn ('More Blah')
  End

PROCEDURES

The syntax for defining a procedure is as follows:

Procedure <Proc Name> (<varname vartype>, <varname vartype>)
  <Code here>

IE:

Procedure Hello_World
  WriteLn ('Hello World')

OR:

Procedure SomeProc (Str String, A Byte)
  WriteLn ('Str = ' + Str)
  WriteLn ('A   = ' + A)
End

OR:

Procedure SomeProc (Str String)
  Var
    Str2 : String,
    Str3 : String
  Begin             <--- The keyword "BEGIN" is ignored by the compiler
  WriteLn (Str)        just to maintain a "Pascal-like" feel.
End

IF THEN/ELSE/END

The syntax of an if/else/end statement:

If <boolean statement> Then
  <True code here>
Else If <boolean statement> Then     (optional)
  <True code here>
Else                            (optional)
  <False code here>
If Not fEof(fptr) Then
  WriteLn ('We''re not at the end of the file.')

The above example is the same as the following example, except we've added an else statement:

If fEof(fptr) = False Then
  WriteLn ('We''re not at the end of the file.')
Else
  WriteLn ('This is the end of the file.')
If A = 1 Then
  WriteLn ('A is 1')
Else If A = 2 Then
  WriteLn ('A is 2')
Else If A = 5 Then
  WriteLn ('A is 5')
Else
  WriteLn ('A is not 1, 2, or 5...')

CASE Statements

This has actually been expanded on from the Pascal standard but still follows the same syntax. It has been expanded to allow CASE of more variable types, such as strings. See the included MPLTEST.MPS for examples.

Var I : Integer = 10

Case I Of
  1 : WriteLn('I = 1')
  2 : Begin
       I:=I+1
       WriteLn('I = 3')
      End
  3,4,5,6,7,8,9: 
    WriteLn('Not 1, 2, or 10')
End
Var S : String = 'ABCDEFG'
  Case S[3] Of
    'A': WriteLn('S[3] = '+S[3])
    'B','C','D': WriteLn('S[3] = '+S[3])
  Else
     WriteLn('This is the default choice')
  End

FUNCTIONS

The syntax for defining a function is as follows:

Function <Function Name> (<varname vartype>) : <result type>

IE:

Function AddTen (Num Byte) : Byte
Begin
  AddTen := Num + 10
End

CONST VARIABLES

The syntax for a constant variable is as follows:

String constants:

Const
  SomeStr = 'Hello World!'

Numerical constants:

Const
  SomeNum = 69

Constant variables, like regular variables, can be separated with a comma:

Const
  SomeNum = 69,
  SomeStr = 'Hello World!'

At the moment, constant variables cannot be used in certain places within the MPE engine. If you are assigning a value to a variable, constant values will not be recognized.

mpl.txt · Last modified: 2016/07/13 22:27 by g00r00