Editing NVSE Expressions

NVSE allows for complex expressions in the context of NVSE aware functions, such as [[Let]], [[Eval]] and [[TestExpr]], and when using the [[Script Compiler Override]]. The following table details the permitted operators

{| class="wikitable" style="width:100%; text-align:left"  align="center" 
!align="left"|Symbol
!align="left"|Precedence
!align="left"|Function
!align="left"|Number of Operands
!align="left"|Description
|-
|style="width:10%;"| := ||style="width:10%;"| 0 ||style="width:20%;"| Assignment ||style="width:10%;"| 2 ||style="width:50%;"| Assigns the value of an expression on the right to the variable or array element on the left. Right-associative. The value of the assignment is the right-most operand. Supports multiple assignment i.e. a := b := c := 0 sets all 3 variables to zero. Assignment of strings creates a copy of the string, whereas assignment of arrays creates a reference to the array. ||
|-
|| {{!}} {{!}} ||1 ||Logical Or ||2 ||True if either expression is true.
|-
|| && ||2 ||Logical And ||2 ||True if both expressions are true.
|-
|| += ||2 ||Add and Assign ||2 ||Adds the expression on the right to the variable or array element on the left.
|-
|| -= ||2 ||Subtract and Assign ||2 ||Subtracts the expression on the right from the variable or array element on the left.
|-
|| *= ||2 ||Multiply and Assign ||2 ||Multiplies the variable or array element on the left by the expression on the right.
|-
|| /= ||2 ||Divide and Assign ||2 ||Divides the variable or array element on the left by the expression on the right.
|-
|| ^= ||2 ||Exponent and Assign ||2 ||Raises the variable or array element on the left to the power of the expression on the right.
|-
|| : ||3 ||Slice/Range ||2 ||Specifies a range of elements in a string or array. For strings, creates a substring. Forarrays, creates a copy of the elements within the range. Range includes the upper element. For strings, negative indices start at the last element and count backwards.
|-
|| :: ||3 ||Make Pair ||2 ||Specifies a key-value pair. The lefthand operand defines the key as a numeric or string value, and the righthand operand defines the value (of any type).
|-
|| == ||4 ||Equality ||2 ||True if the operands are equal. Operands must be comparable to each other.
|-
|| != ||4 ||Inequality ||2 ||True if the operands are not equal.
|-
|| > ||5 ||Greater Than ||2 ||Operands must be comparable and ordered. For strings, comparison is case-insensitive.
|-
|| < ||5 ||Less Than ||2 ||For strings, case-insensitive.
|-
|| >= ||5 ||Greater or Equal ||2 ||For strings, case-insensitive.
|-
|| <= ||5 ||Less than or Equal ||2 ||For strings, case-insensitive.
|-
|| | ||6 ||Bitwise Or ||2 ||Performs a bitwise or, demoting the operands to integers.
|-
|| & ||7 ||Bitwise And ||2 ||Performs a bitwise and, demoting the operands to integers.
|-
|| << ||8 ||Binary Left Shift ||2 ||Shifts left operand left by specified number of bits, demoting both operands to integers.
|-
|| >> ||8 ||Binary Right Shift ||2 ||Shifts left operand right by specified number of bits, demoting both operands to integers.
|-
|| + ||9 ||Addition/Concatentation ||2 ||Adds two numbers or joins two strings.
|-
|| - ||9 ||Subtraction ||2 ||Self-explanatory.
|-
|| * ||10 ||Multiplication ||2 ||Self-explanatory.
|-
|| / ||10 ||Division ||2 ||Self-explanatory.
|-
|| % ||10 ||Modulo ||2 ||Returns the remainder of integer division.
|-
|| ^ ||11 ||Exponentiation ||2 ||Raises left operand to the power of the right operand.
|-
|| - ||12 ||Negation ||1 ||Returns the opposite of an expression.
|-
|| $ ||12 ||Stringize ||1 ||Returns a string representation of an expression. (Shorthand for ToString).
|-
|| # ||12 ||Numericize ||1 ||Returns the numeric value of a string. (Shorthand for ToNumber).
|-
|| * ||12 ||Dereference/Unbox ||1 ||Dereferences an array. If the array is a StringMap with a "value" key, returns thevalue associated with that key. Otherwise returns the value of the first element.
|-
|| & ||12 ||Box ||1 ||"Boxes" a value of any type, returning an Array containing that value as its only element. The value can be retrieved with the unary * (unbox) operator.
|-
|| ! ||13 ||Logical Not ||1 ||Returns the opposite of a boolean expression. i.e. !(true) evaluates to false.
|-
|| ( ) ||14 ||Parentheses ||0 ||Enclose expressions within parentheses to override default precedence rules.
|-
|| [ ] ||15 ||Subscript ||2 ||For arrays, accesses the element having the specified key. For strings, returns a stringcontaining the single character at the specified position. The expression within the brackets is treated as if it were parenthesized (overrides precedence rules).
|-
|| -> ||15 ||Member Access ||2 ||The lefthand operand is a StringMap having a key specified by the righthand operand. Returns the value associated with that key. Example: 'dict->key' is equivalent to 'dict["key"]'
|-
|-
|}

==A Few Examples==
<pre>
; assign a variable
let MyInt := 5

; reference a single entry from an array, or character from a string
my_array[4] ; * element at index 4

; reference a substring of a string_var (or sub array)
let my_string := "this is my full string"
my_string[0:3] == "this"
my_string[-6:-1] == "string" ; * you can use negative indices to reference via the end

; * concatanate strings, use the stringize operator, and nested functions:
Print "this is sunny's name: " + $SunnyREF + " and a nested function too: " + $(GetNVSEVersion)

; 'this is sunny's name: Sunny Smiles and a nested function too: 4'

while (x += 1) < 5 ; increment x, then loop if less then 5
    ...

if TestExpr MyArray[x] ; see if my array has element x
   ...

if eval !(SunnyREF.GetDead) ; if sunny is not dead
   ...
</pre>

==See Also==
*[[Let]]
*[[Eval]]
*[[TestExpr]]
*[[While]]
*[[ForEach]]
*[[Print]] / [[PrintDebug]]
*[[Script Compiler Override]]

==External Links==
*[http://obse.silverlock.org/obse_command_doc.html#OBSE_Expressions This page is adapted from a section in the official OBSE docs]
*[http://fallout.bethsoft.com/eng/links/privacyredirect.php?site=http://www.loverslab.com/topic/26749-tutorial-nvse4-part-1-syntax-and-expressions/ A tutorial on syntax and expressions in NVSE 4]

[[Category:NVSE]]
[[Category:Expressions]]
[[Category:Scripting]]
@@ Line 102: / Line 102: @@
      ...
-if TestExpr MyRef := MyArray[x] ; assign MyRef to array element x, if this index exists
+if TestExpr MyArray[x] ; see if my array has element x
     ...
 if eval !(SunnyREF.GetDead) ; if sunny is not dead
     ...
-foreach entry <- SomeArray
-   let MyRef := *entry     ; 'Unbox' is equivalent to using entry["value"]
-   ...
-; boxing a ref into a single entry array allows passage as an argument of this type:
-call MyUDF &MyRef
 </pre>