Operators and Keywords · codingseb/ExpressionEvaluator Wiki ·

ExpressionEvaluator manage a large set of C# operators (See C# Operators)

ExpressionEvaluator respect the C# precedence rules of operators

Here is a list of which operators are supported in ExpressionEvaluator or not

Type	Operator	Description	Support
Primary	x.y	Member access	Supported
Primary	x?.y	Null-conditional Member access	Supported
Primary	x?[y]	Null-conditional index	Supported
Primary	f(x)	Invocation	Supported
Primary	a[x]	Index	Supported
Primary	x++	Postfix increment	Supported Warning change the state of the postfixed element
Primary	x--	Postfix decrement	Supported Warning change the state of the postfixed element
Primary	new	Instanciate	Supported you can also use new() function
Primary	typeof	Get the System.Type instance for a type	Supported
Primary	checked	Enable overflow checking	Not Supported
Primary	unchecked	Disable overflow checking	Not Supported
Primary	default(T)	Default value of a type	Supported
Primary	delegate	Anonymous method	Not Supported
Primary	sizeof	Number of bytes used by a variable or a type	Supported
Primary	->	Dereference	Not Supported
Unary	+x	Positive value	Supported
Unary	-x	Negative value	Supported
Unary	!x	Logical Negation	Supported
Unary	~x	Bitwise complement	Supported
Unary	++x	Prefix increment	Supported Warning change the state of the prefixed element
Unary	--x	Prefix decrement	Supported Warning change the state of the prefixed element
Unary	(T)x	Explicit cast	Supported
Unary	await	Await (for async methods)	Not Supported
Unary	&x	Adress of	Not Supported
Unary	*x	Pointer indirection	Not Supported
Multiplicative	x * y	Multiplication	Supported
Multiplicative	x / y	Division	Supported
Multiplicative	x % y	Modulus (Integer remainder)	Supported
Additive	x + y	Addition	Supported
Additive	x - y	Substraction	Supported
Shift	x << y	Left shift (bits)	Supported
Shift	x >> y	Right shift (bits)	Supported
Relational	x < y	Less than	Supported
Relational	x > y	Greater than	Supported
Relational	x <= y	Less than or equal	Supported
Relational	x >= y	Greater than or equal	Supported
Type-testing	is	Type testing	Supported
Type-testing	as	Type conversion	Not Supported
Equality	x == y	Equality comparison	Supported
Equality	x != y	Not equal	Supported
Logical AND	x & y	Logical and (bits)	Supported
Logical XOR	x ^ y	Logical XOR (bits)	Supported
Logical OR	x \| y	Logical OR (bits)	Supported
Conditional AND	x && y	Conditional and (booleans)	Supported
Conditional OR	x \|\| y	Conditional or (booleans)	Supported
Null-coalescing	x ?? y	Null coalescing (if null take that)	Supported
Conditional	t ? x : y	Ternary conditional operator	Supported
Lambda	=>	Lambda (Expressions and bodied)	Supported

If you are not totally happy with these operators. There are also advanced ways to add, remove or redefine operators

Warning all of the following operators change the value of their left element.

Assignation operators (and also postfix operators (++ and --)) are usable on :

Elements	What is changing	Options
Custom variables	The variable in the Variables dictionary is changed and if the variable doesn't exists, it automatically created with the = operator	Can be disabled with `evaluator.OptionVariableAssignationActive = false;`
Properties or fields on objects	If the property/field is not readonly it is changed	Can be disabled with `evaluator.OptionPropertyOrFieldSetActive = false;`
Indexed object like arrays, list or dictionaries	The value at the specified index is changed	Can be disabled with `evaluator.OptionIndexingAssignationActive = false;`

Here is the list of available assignation operator

Operator	Support
=	Supported (Can be use to declare a new variable that will be injected in the Variables dictionary)
+=	Supported
-=	Supported
*=	Supported
/=	Supported
%=	Supported
&=	Supported
\|=	Supported
^=	Supported
<<=	Supported
>>=	Supported
??=	Supported (From version 1.4.17.0)

An assignation of a variable that do not exists create it from the script. See Declare and init variables in scripts

In addition to simple expression evaluation you can also evaluate small scripts with the method :

//object ScriptEvaluate(string script)
evaluator.ScriptEvaluate(script);

Scripts are just a serie of expressions to evaluate separated with a ; character and leaded by severals additionals keywords.

Currently the following scripts keywords are supported

Type	Keyword	Support
Selection	if	Supported
Selection	else if	Supported
Selection	else	Supported
Selection	switch case	Not yet supported
Iteration	do ... while	Supported
Iteration	for	Supported
Iteration	foreach, in	Supported
Iteration	while	Supported
Jump	break	Supported in do, for and while blocks
Jump	continue	Supported in do, for and while blocks
Jump	goto	Not supported (But if you looked after it -> Booo !!! Bad code)
Jump	return	Supported
Jump/Exception	throw	Supported
Exception Handling	try-catch	Supported
Exception Handling	try-finally	Supported
Exception Handling	try-catch-finally	Supported

Remark : The way ScriptEvaluate works is to evaluate expressions one by one. There is no syntax check before the evaluation. So be aware that syntax or naming bugs only appears in execution and some code can already be evaluated at this time. Futhermore a syntaxic/naming bug in an if-else block for example can simply be ignored until the corresponding condition is met to evaluate the specific line of code.

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