What does -1e10 mean

[suresh]

I see this in many plot statements. what does -1e10 represent?

[fxshrat]

Please use forum search before posting!

How do i determine if a variable exist?

Keep in mind that in C/C++ NULL is just a 0 (number zero). It is defined in the header files as: #define NULL 0 C/C++ NULL does not have special meaning as Null (aka. Empty) in AFL1 . So the check you are doing is highly unreliable as you are just checking if variable is equal zero. Your code only "appears" to work. If this variable happens to be zero your code would think it does not exist, while it really exists. To really find out that variable does not exist there is documented way (see …

-> Quote from there:

Null in AFL is a special "magic" value, different than zero (currently -1e10, but don't hardcode that), and it has special meaning. It means "unknown" or "empty". It is used to mark bars where data are not available / not known, for example for the very first 19 bars of 20-bar simple moving average.

-1e10 itself is very large (negative) number -> -10000000000.
See here also.

In order to check for NULL (-1e10) you should use IsNull() function.

[Tomasz]

I see this in many plot statements.

This means that these statements are incorrectly written. You should never ever use hard coded -1e10 value. You should always use Null constant instead.

[bluesinvestor]

is this still valid in ADK (Plugin.h):

// useful macros for empty values
#define EMPTY_VAL (-1e10f)

[Tomasz]

Yes it is but you should not hard code any numeric values. Use Null in AFL, or EMPTY_VAL in DLL.