AviSynth Syntax - Boolean functions

Boolean functions return true or false, if the condition that they test holds or not, respectively.

IsBool

IsBool(var)

Tests if var is of the bool type. var can be any expression allowed by the AviSynth Syntax.

Examples:

b = false
IsBool(b) = true
IsBool(1 < 2 && 0 == 1) = true
IsBool(123) = false

IsClip

IsClip(var)

Tests if var is of the clip type. var can be any expression allowed by the AviSynth Syntax.

Examples:

c = AviSource(...)
IsClip(c) = true
IsClip("c") = false

IsFloat

IsFloat(var)

Tests if var is of the float type. var can be any expression allowed by the AviSynth Syntax.

Examples:

f = Sqrt(2)
IsFloat(f) = true
IsFloat(true) = false
IsFloat("42.") = false
IsFloat(2) = true   # ints are considered to be floats by this function
IsReallyFloat(2) = false # see below

As a workaround for the issue noted above, you may use the following user function:

## return true for floats only
function IsReallyFloat(val v)
{
    return (IsInt(v)==false) && IsFloat(v)
}

IsInt

IsInt(var)

Tests if var is of the int type. var can be any expression allowed by the AviSynth Syntax.

Examples:

IsInt(2) = true
IsInt(2.1) = false
IsInt(true) = false

IsString

IsString(var)

Tests if var is of the string type. var can be any expression allowed by the AviSynth Syntax.

Examples:

IsString("test") = true
IsString(2.3) = false
IsString(String(2.3)) = true

IsFunction

IsFunction(var)

Tests if var is of the function type. var can be any expression allowed by the AviSynth Syntax.

Examples:

function MyFunc(clip c) {
  return c.Invert()
}

IsFunction("MyFunc") = true

Defined

Defined(var)

Tests if var is defined. Can be used inside Script functions to test if an optional argument has been given an explicit value. More formally, the function returns false if its argument (normally a function argument or variable) has the void ('undefined') type, otherwise it returns true.

Examples:

b_arg_supplied = Defined(arg)
myvar = b_arg_supplied ? ... : ...

Exist

Exist(string filename)

Tests if the file specified by filename exists.

Examples:

filename = ...
clp = Exist(filename) ? AviSource(filename) : Assert(false,
\ "file: " + filename + " does not exist")

FunctionExists

FunctionExists(string name)

Tests if the function or filter or clip property name is defined in the script.

Examples:

## using a filter only if it exists (AVS+ only)
ColorBars
return FunctionExists("MyFilter")
\ ? Apply("MyFilter", Last, "TEST")
\ : Last

InternalFunctionExists

InternalFunctionExists(string name)

Tests if the function, filter or property name is defined natively within AviSynth+.

Unlike FunctionExists, returns false for external plugins and user-defined functions.

VarExist

VarExist(string name)

Tests if the "name" variable exists or not.

Note: if variable exists, it returns true regardless of the "defined" state of the variable.

Changelog

Version	Changes
Avisynth+	Added "IsFunction" Added "FunctionExists" Added "InternalFunctionExists" Added "VarExist"

Back to Internal functions.

$Date: 2024/01/05 10:54:00 $