Operators
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Revision as of 19:11, 5 December 2015
As in all programming and scripting languages, operators in AviSynth script language allow the performance of actions (operations) onto variables. Operators form the basis for building up expressions, the building blocks of AviSynth scripts.
AviSynth operators follow loosely the same rules as C operators, regarding meaning, precedence and associativity. By loosely we mean that there are some exceptions, indicated in the text below.
Note that when a binary operator is applied to an int and a float, the int is first converted to float, as in C.
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For All Variable Types
For all types of operands (clip, int, float, string, bool) you can use the following operators:
| == | is equal |
| != | not equal |
| <> | not equal (alternative to !=, v2.07) |
String comparisons are not case-sensitive, so "abc" == "ABC" returns true.
For Numbers
For numeric types (int, float) you can use the following int/float-specific operators:
| + | add |
| - | subtract |
| * | multiply |
| / | divide |
| % | mod |
| >= | greater or equal than |
| <= | less or equal than |
| < | less than |
| > | greater than |
AviSynth in former versions parsed expressions from right to left, which gave unexpected results. For example:
- a = 10 - 5 - 5 resulted in 10 - (5 - 5) = 10 instead of (10 - 5) - 5 = 0 !
- b = 100. / 2. / 4. resulted in 100. / (2. / 4.) = 200 instead of (100. / 2.) / 4. = 12.5 !
These "bugs" have been corrected in v2.53!
For Strings
For string type you can use the following string-specific operators:
| + | concatenate |
| >= | greater or equal than (v2.07) |
| <= | less or equal than (v2.07) |
| < | less than (v2.07) |
| > | greater than (v2.07) |
Like the equality operator, these string comparisons are case-insensitive.
For Clips
For clip type you can use the following clip-specific operators:
| + | the same as the function UnalignedSplice |
| ++ | the same as the function AlignedSplice |
For Booleans
For bool type (true/false) you can use the following bool-specific operators:
| || | or |
| && | and |
| ?: | execute code conditionally |
| ! | not |
The conditional execution operator is used as in the following example:
b = (a==true) ? 1 : 2
This means in pseudo-basic:
if (a=true) then b=1 else b=2
From version v2.07, AviSynth provides a NOP() function which can be used inside a conditional execution block in cases where "else" may not otherwise be desirable (such as a conditional Import or LoadPlugin).
Operator Precedence
The precedence of AviSynth operators is presented at the table below. Operators higher to the top of the table have higher precedence. Operators inside the same row have the same order of precedence.
| * | / | % | ||||
| + | ++ | - | ||||
| < | > | <= | >= | != | <> | == |
| && | ||||||
| || | ||||||
| ?: | ||||||
The dot symbol (.), used in the "OOP notation" for a function call, is not strictly an operator, but effectively has a higher precedence than any operator symbol.
So for example, a + b.f(args) means a + f(b, args) and not f(a+b, args) (which could be written as (a+b).f(args))
Back to AviSynth Syntax.
