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TJ,
functions in AFL, cool! That was
the last missing part!
Thanks!
UM
<BLOCKQUOTE
>
----- Original Message -----
<DIV
>From:
Tomasz Janeczko
To: <A title=amibroker@xxxxxxxxxxxxxxx
href="">amibroker@xxxxxxxxxxxxxxx
Sent: Wednesday, April 30, 2003 1:50
PM
Subject: [amibroker] AmiBroker 4.34.0
BETA released - now with user-definable functions with arguments and local
variables
Hello,
A new beta version (4.34.0) of AmiBroker has just been
released.
It is available for registered users only from the members
area at:
<A
href="">http://www.amibroker.com/members/bin/ab4340beta.exe
If you forgot your user name / password to the members
area
you can use automatic reminder service at: <A
href="">http://www.amibroker.com/login.html
The highlight of this release are user definable functions /
procedures
allowing passing parameters and supporting local variables.
Please read "HELP ON NEW FEATURES" section below for the
details.
The description of remaining additions is included in the CHANGE
LOG
later in this document.
Best regards,Tomasz
Janeczkoamibroker.com
AmiBroker 4.34.0 Beta Read Me
April 30, 2003 13:42
THIS IS AN EARLY BETA VERSION OF THE SOFTWARE. EXPECT BUGS
!!!
AGAIN: THIS IS AN EARLY BETA VERSION OF THE SOFTWARE. EXPECT BUGS
!!!
Backup your data files and entire AmiBroker folder
first!
INSTALLATION INSTRUCTIONS
IMPORTANT: This archive is update-only. You have to install full
version 4.30 first.
Just run the installer and follow the instructions.
Then run AmiBroker. You should see "AmiBroker 4.34.0 beta" written in the
About box.
HELP ON NEW FEATURES
USER-DEFINABLE FUNCTIONS, PROCEDURES, LOCAL/GLOBAL VARIABLES (4.34 or
higher)
Here is a sample code showing user-defined function:
// the following function is 2nd order smoother
function IIR2( input, f0, f1, f2 ){ result[ 0 ] =
input[ 0 ]; result[ 1 ] = input[ 1 ];
for( i = 2; i < BarCount; i++
) { result[ i ] = f0 * input[ i ] +
f1 * result[ i - 1 ] +
f2 * result[ i - 2 ]; }
return result;}
Plot( Close, "Price", colorBlack, styleCandle );Plot( IIR2(
Close, 0.2, 1.4, -0.6 ), "function example", colorRed );
In this code IIR2 is a user-defined function. input, f0, f1,
f2 are formal parameters of the functions.At the time of function call
the values of arguments are passed in these variables. Formal parameters
behave like local variables.Later we have result and i which
are local variables. Local variables are visible inside function only. If any
other function uses the same variable name they won't interfere between each
other.
Due to the fact that AFL does not require to declare variables the decision
whenever given variable is treated as local or global is taken depending on
where it is FIRST USED.
If given identifier appears first INSIDE function definition - then it is
treated as LOCAL variable.If given identifier appears first OUTSIDE
function definition - then it is treated as GLOBAL variable.
Example (commentary):
k = 4; // this is GLOBAL variable
function f( x ){ z = 3; // this is LOCAL
variable return z * x * k; // 'k' here references
global variable k (first used above outside
function)}
z = 5; // this is GLOBAL variable with the same name as local
variable in function f
"The value of z before function call :" + WriteVal( z );
// Now even if we call function // the value of our global
variable z // is not affected by function call because// global
variable z and local variable z are separate and // arguments are passed
by value (not by reference)
"The result of f( z ) = " + WriteVal( f( z ) );
"The value of z after function call is unchanged : " + WriteVal( z
);
At the end of the function we can see 'return' statement that is used to
return the result to the caller. Note that currently return statement must be
placed at the very end of the function.
It is also possible to write a procedure (a function that returns nothing
(void))
procedure SinePlotter( Freq, ColorIndex ){ pname =
"Line"+WriteVal(ColorIndex,1.0); array = sin( Cum( Freq * 0.01
) ); Plot( array, pname , colorRed + ColorIndex, styleThick
);}
for( n = 1; n < 10; n++ ){ SinePlotter(
n/2+Cum(0.01), n );}
Note that although there are two separate keywords 'function' and
'procedure' AmiBroker currently treats them the same (they both accept return
values but not require them), but in the future the rules maight get enforced
to usereturn statement ONLY in conjunction with function keyword. So it is
advised to use function keyword in case when your function returns any value
and procedure keyword otherwise.
Note also that recursion (having a function call itself from within itself)
is NOT supported as for now.
FLOW CONTROL AND
LOOPING (4.31 or higher)
while Statement
The while statement lets you repeat a statement until a specified
expression becomes false.
Syntax
while ( expression ) statement
The expression must have arithmetic (numeric/boolean) type.
Execution proceeds as follows:
The expression is evaluated.
If expression is initially false, the body of the while
statement is never executed, and control passes from the while
statement to the next statement in the program.
If expression is true (nonzero), the body of the
statement is executed and the process is repeated beginning at step
1.
This is an example of the while statement: i = 10;while( i < 20 ){ Plot( MA( Close, i ), "MA" + WriteVal( i, 0 ), colorBlack + i ); i = i + 1;}
The example plots 10, 11, 12, 13, 14, 15, 16, 17, 18, 19
- bar moving averages.
for Statement
The for statement lets you repeat a statement or compound statement
a specified number of times. The body of a for statement is executed
zero or more times until an optional condition becomes false.
Syntax
for ( init-expression ;
cond-expression ; loop-expression )
statement
Execution of a for statement proceeds as follows:
The init-expression, is evaluated. This specifies the
initialization for the loop. There is no restriction on the type of
init-expression.
The cond-expression, is evaluated. This expression must
have arithmetic type. It is evaluated before each iteration. Three results
are possible:
If cond-expression is true (nonzero), statement is
executed; then loop-expression, if any, is evaluated. The
loop-expression is evaluated after each iteration. There is no
restriction on its type. Side effects will execute in order. The process
then begins again with the evaluation of cond-expression.
If cond-expression is false (0), execution of the for
statement terminates and control passes to the next statement in the
program.
This example illustrates the for statement: myema[ 0 ] = Close[ 0 ];for( i = 1; i < BarCount; i++ ){ myema[ i ] = 0.1 * Close[ i ] + 0.9 * myema[ i - 1 ];}This example iterates all bars of close array to calculate exponential moving average
if, else Statements
if( expression )statement1 [else
statement2]
The if keyword executes statement1 if expression is
true (nonzero); if else is present and expression is false
(zero), it executes statement2. After executing statement1 or
statement2, control passes to the next statement.
Example 1if ( i > 0 )
y = x / i;
else
{
x = i;
y = abs( x );
}
In this example, the statement y = x/i; is executed if
i is greater than 0. If i is less than or equal to
0, i is assigned to x and <FONT
face="Courier New">abs( x ) is assigned to y.
Note that the statement forming the if clause ends with a
semicolon.
When nesting if statements and else clauses, use braces to
group the statements and clauses into compound statements that clarify your
intent. If no braces are present, the compiler resolves ambiguities by
associating each else with the closest if that lacks an
else.
Example 2if ( i > 0 ) /* Without braces */
if ( j > i )
x = j;
else
x = i;
The else clause is associated with the inner if statement in
this example. If i is less than or equal to 0, no value is
assigned to x.
Example 3if ( i > 0 )
{ /* With braces */
if ( j > i )
x = j;
}
else
x = i;
The braces surrounding the inner if statement in this example make
the else clause part of the outer if statement. If
i is less than or equal to 0, i is assigned to
x.
CHANGE LOG
CHANGES FOR VERSION
4.34.0 (as compared to 4.33.0)
user-definable
functions and procedures with parameters and local variables
'A' is NO LONGER
predefined symbol. I decided to remove it because people tend to use A as
user-variable forgetting the fact that it was build-in array holding typical
price (H+L+C)/3. Use 'Avg' instead.
indicator list column width increased in Indicator Builder
DayOfYear - returns the calendar day number counting from beginning of
the year January 1st is 1. Maximum number returned is 366
CHANGES FOR VERSION
4.33.0 (as compared to 4.32.2)
Database purify tool implemented (available via Tools->Database
Purify)allows to detect missing/extra quotes, possible splits, invalid
OHLC relationshipApply to/range settings similar to AA window. You
can also right click over result list to add symbols to watch list and copy
the list to the clipboard (and paste it later to any other program for
futher use)
further improvements to AFL garbage collector, now looping regardless of
loop count requires the same amount of memory as just single pass of the
code (no growing allocated memory during loops).This enormously lowered
memory consumption for some formulas and increased the speed of some loops
3..4 times.
added variable period support to the following
functions:LinRegSlope,LinearReg,LinRegIntercept,StdErr,TSF
Sample code:
Plot( Close, "Test", colorBlack );
range = 15 * MA( ATR( 15 ), 50 ) / ATR( 15 );
//Plot( range, "range", colorBlue, styleOwnScale );Plot( LinearReg(
Close, range ), "Test", colorRed );
fixed sometimes incorrect output of variable-period version of
LLV/HHV
fixed crash occuring when bad arguments were passed to the function (bug
introduced in 4.32.x).
CHANGES FOR VERSION
4.32.2 (as compared to 4.32.1)
second bug in experimental garbage collector fixed.
CHANGES FOR VERSION
4.32.1 (as compared to 4.32.0)
garbage collector was releasing memory too soon in some cases, now
fixed.
CHANGES FOR VERSION
4.32.0 (as compared to 4.31.1)
added type check in IF/ELSE statements
added type check in array element assignment
error messages now numbered and display changed slightly
you can break running loop by pressing Shift+BREAK (Pause) key
combination
calling COM objects works again (was broken in 4.31.x)
changed slightly the way TAB works in editor, if TAB is pressed any
selection is deselected to avoid accidential deletion of text
experimental: added 'agressive garbage collector' that extremely
decreases the amountof memory required to run AFL formula by releasing
the memoryused for temporary variables as soon as possible
(previouslytemporary memory was released at the end of formula
execution).A side-effect of new garbage collector is some speed up in
formula execution.
new tab in preferences for AFL engine settings
experimental feature, NOT for beginners, may be removed/modified in
future releases: new _TRACE( "string" ) AFL function addedthat
allows to write debug messages from AFL code to system debug viewer.(it
calls internally OutputDebugString Win API function).To view debug
messages you have to run DebugView freeware program from
http://www.sysinternals.com/
CHANGES FOR VERSION
4.31.1 (as compared to 4.31.0)
fixed bug introduced in 4.31.0 causing no text output in
commentary/interpretation
CHANGES FOR VERSION
4.31.0 (as compared to 4.30.0)
Workspace window uses "icon font" set in the Windows settings instead of
hard coded Tahoma 8
for better readability and ClearType(tm) compatibility on WinXP, all
dialog windows use now 'MS Shell Dlg' face name that maps to standard MS
Sans Serif on Win 9x/Me/NT and Tahoma on Win 2K and XP.
rewritten AFL parser, now formula is parsed and coverted to syntax tree
and then interpreted. This would allow further improvements including
compilation. This allowed also to add loops/if-else statements.
implemented IF/ELSE statement, WHILE and FOR loops:The same basic
'for' loop in AFL is 2..3 times faster than in JScriptSyntax follows
C++/JScript style:
while( conditional_expression ) statement;
for( initializer_part; conditional_expression; iterator_part )
statement;
if( conditional_expression ) statement;
if( conditional_expression )
statement;elsestatement;
implemented compound statements: these are blocks of statements
enclosedin opening and closing curly brace
{statement1;statement2;...statementN;}
compound statement can appear anywhere when simple statement can.
For example:
i = 10;while( i < 20 ){Plot( MA( Close, i ), "MA" +
WriteVal( i, 0 ), colorBlack + i );i = i + 1;}
implemented C-style postfix and prefix increment/decrement operators
i = 10;WriteIf( i++ );WriteIf( ++i );WriteIf( i
);
implemented array element access (subscript) operator []:
WriteVal( Close[ 0 ] ); // prints the first bar of close
array
/* a sample low-level implementation of exponential moving average
in AFL */
myema[ 0 ] = Close[ 0 ];
for( i = 1; i < BarCount; i++ ){myema[ i ] = 0.1 *
Close[ i ] + 0.9 * myema[ i - 1 ];}
added built-in constant 'BarCount' that returns number of bars available
in arrays (the number of elements of array)When QuickAFL is turned on it
may be less than true number of bars because QuickAFL feature attempts to
use only visible bars (and few before). You can control how many bars the
formula requires using SetBarsRequired() function
implemented infinite-loop protection. Nice if you forgot to increment
counter variable in 'for' loop :-)
tab key now works without need to press ALT/CTRL in AFL editors
added C-like synonyms for logical ADD/OR/NOT: &&, ||, !
/* a sample low-level implementation of Profit-target stop in
AFL: */
Buy = Cross( MACD(), Signal() );
priceatbuy=0;
for( i = 0; i < BarCount; i++
){ if( priceatbuy == 0 && Buy[
i ] ) priceatbuy = BuyPrice[ i
];
if( priceatbuy > 0 &&
SellPrice[ i ] > 1.1 * priceatbuy
) { Sell[
i ] = 1; SellPrice[ i ] = 1.1 *
priceatbuy; priceatbuy =
0; } else Sell[
i ] = 0;}
/* sample EMA rainbow */
Plot( Close, "Price", colorBlack, styleCandle );for( Range =
15; Range < 100; Range++ ) Plot( EMA( Close, Range
), "MA"+WriteVal(Range,0), colorRose + Range % 8, styleNoLabel );
HOW TO REPORT BUGS
If you experience any problem with this beta version please send detailed
description of the problem (especially the steps needed to reproduce it) to <A
href="">bugs@xxxxxxxxxxxxx Send
BUG REPORTS to bugs@xxxxxxxxxxxxxSend SUGGESTIONS to
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