|
PureBytes Links
Trading Reference Links
|
Title: Message
very
professional. thanks jose..
Some poor MetaStock coding practices
worth avoiding:
1) MetaStock's PREV function slows down processing
dramatically - its
use should be avoided wherever possible. Placing
unnecessary PREV
functions in a formula generally reflects poor
programming skills;
2) Rather than create a zillion formulae with
different hard-coded
parameters scattered inside the formula, assign these
values to
parameters so they may be easily changed as required;
3)
Always use meaningful names for variables. The code may need to be
followed and understood by others, or worse still, Alzheimer's may
just be around the corner;
4) Use {comments} wherever possible, for
the same reasons as #3.
Here is a recent example of code that
ignores the above four points:
========================
3% envelope
14 MA Expert
========================
---8<--------------
Long
A:=C>1.03*Mov(C,14,S);
B:=C<.97*Mov(C,14,S);
D:=If(A,1,If(B,0,PREV));
D=1
Short
A:=C>1.03*Mov(C,14,S);
B:=C<.97*Mov(C,14,S);
D:=If(A,1,If(B,0,PREV));
D=0
Symbol tab
Long
A:=C>1.03*Mov(C,14,S);
B:=C<.97*Mov(C,14,S);
D:=If(A,1,If(B,0,PREV));
D=1 AND Ref(D,-1)=0
short
A:=C>1.03*Mov(C,14,S);
B:=C<.97*Mov(C,14,S);
D:=If(A,1,If(B,0,PREV));
D=0 AND
Ref(D,-1)=1
---8<--------------
The code above is an example of
poor coding in MetaStock, because:
1) Four (unnecessary) PREV function
slows down the plotting of the
Expert signals, and would dramatically slow
down an exploration based
on this code;
2) No parameters assigned
to global variables - it would take some
effort to change the 16 values,
and there is always the risk of
introducing errors;
3) No
meaningful names assigned to variables. Try following the code
of
some of the longer formulae, and the problem becomes apparent;
4) No
{comments} used. The author may not need them, but others could
do
with some.
The code below plots the same signals, and:
1)
Avoids PREV functions;
2) Assigns global variables to variables at the
easy-to-get head of
the formula;
3) Uses names for variables that
reflect their intended use;
4 {Comments}, {Comments},
{Comments}.
===========================
14 SMA / 3% envelope
Expert
===========================
Highlights tab:
Long
---8<----------
{ Variables
}
SMAperiods:=14;
EnvPercent:=3;
{ Envelope signals
}
Env:=EnvPercent/100;
upper:=C>(1+Env)*Mov(C,SMAperiods,S);
lower:=C<(1-Env)*Mov(C,SMAperiods,S);
{ Trade binary flag
}
binary:=ValueWhen(1,upper-lower<>0,upper-lower);
{ Long
trade flag }
binary=1
---8<----------
Short
---8<----------
{ Variables
}
SMAperiods:=14;
EnvPercent:=3;
{ Envelope signals
}
Env:=EnvPercent/100;
upper:=C>(1+Env)*Mov(C,SMAperiods,S);
lower:=C<(1-Env)*Mov(C,SMAperiods,S);
{ Trade binary flag
}
binary:=ValueWhen(1,upper-lower<>0,upper-lower);
{ Short
trade flag }
binary=0
---8<----------
Symbols
tab:
Long
---8<----------
{ Variables
}
SMAperiods:=14;
EnvPercent:=3;
{ Envelope signals
}
Env:=EnvPercent/100;
upper:=C>(1+Env)*Mov(C,SMAperiods,S);
lower:=C<(1-Env)*Mov(C,SMAperiods,S);
{ Trade binary flag
}
binary:=ValueWhen(1,upper-lower<>0,upper-lower);
{ Long
trade - first signal }
long:=binary=1 AND
Alert(binary<1,2);
long
---8<----------
Short
---8<----------
{ Variables
}
SMAperiods:=14;
EnvPercent:=3;
{ Envelope signals
}
Env:=EnvPercent/100;
upper:=C>(1+Env)*Mov(C,SMAperiods,S);
lower:=C<(1-Env)*Mov(C,SMAperiods,S);
{ Trade binary flag
}
binary:=ValueWhen(1,upper-lower<>0,upper-lower);
{ Short
trade - first signal }
short:=binary<1 AND
Alert(binary>0,2);
short
---8<----------
Life is so
much easier with clean, annotated code... ;)
jose '-)
http://www.metastocktools.com
Yahoo! Groups Links
|