Simulation expressions

This reference lists the expression language used throughout simulation properties — the input modes, data types, operators, and every built-in function. An expression is an arithmetic or logical statement that computes a value while the simulation runs; it can use variables, custom functions, and the built-in functions below.

How you enter an expression

Every expression box has a mode, switched with the dropdown at its right edge:

Mode	Use for
Constant	A plain value — a number or true/false. The fastest way to say a task takes exactly 1 minute.
Expression	The full language: variables, functions, operators. Typing opens autocomplete with the variables in your model and the built-in functions; hovering a suggestion shows what it does, and entering a function's parentheses shows the name and order of its parameters.
Between (Uniform)	Two bounds; each evaluation returns a uniformly distributed value between them.
Between (Normal)	Two bounds; each evaluation returns a normally distributed value between them — most results near the middle, few at the edges.
Fit Data	Derives a distribution from data you supply: pick a column, and a distribution (Uniform, Normal, LogNormal, Exponential, or Weibull) is auto-selected by the lowest AD Score, with the alternatives listed for you to confirm or override.
Convert to Scenario Variable	Replaces the constant with a new Scenario variable, so the value can vary per scenario and with Run all scenarios.

Expressions are checked when you leave the box. A Warning means the expression can still evaluate but may do something unexpected; an Error means it cannot run, and the simulation won't start until you fix it.

Data types

Type	Values
Number	With or without decimals: 5, 10.25.
Text	Anything in quotation marks: "High priority".
True/false	true or false.
Table	A table variable; read one cell as Variable[Row, Column].

Operators

Operations are evaluated in the order of this table; use parentheses to override it.

Operation	Description
-x	Negates x.
x ^ y	x raised to the power y.
x * y	Multiplication.
x / y	Division.
x % y	Remainder of x divided by y.
x + y	Addition.
x - y	Subtraction.
x <= y, x < y, x >= y, x > y	Numeric comparison; true or false.
x != y	True when x and y differ.
x = y, x == y	True when x and y are equal.
!x	Turns true into false and false into true.
x and y	True when both are true.
x or y	True unless both are false.
if x then y else z	y when x is true, otherwise z.
x ? y : z	The same conditional, written compactly.

Time functions

Function	Description	Syntax
ElapsedTime	Returns the time elapsed since the start of the simulation, in seconds. After four simulated hours, ElapsedTime() = 14400.	ElapsedTime()
TotalTime	Returns the total time the simulation will run, in seconds. For a four-hour run, TotalTime() = 14400. Throws an error when the run has no set time (for example, it ends by cases completed).	TotalTime()

Logical functions

Function	Description	Syntax
If	Returns a value based on a test. When Test is true, returns the Then value; otherwise the Else value. A numeric Test counts as true when nonzero; a text Test counts as true when not empty. Extra parameter pairs act as ElseIf branches: when the first test is false, the next test is evaluated, and so on.	If(Test,Then,Else) · If(Test,Then,ElseIfTest,Then,…,Else)
IsEmpty	Returns 1 when String is "", else 0.	IsEmpty(String)
IsNum	Returns 1 when Value is numeric, else 0.	IsNum(Value)
Select	Returns a value by integer index: 0 returns Case0, 1 returns Case1, and so on. Out of bounds returns Default.	Select(CaseNum,Default,Case0,…CaseN)
Switch	Compares SwitchValue against each Value and returns the paired Result of the first match, or Default when none match.	Switch(SwitchValue,Default,Value1,Result1,…ValueN,ResultN)

Numeric functions

Function	Description	Syntax
Abs	The absolute value: Abs(-4) = 4.	Abs(Num)
Ceiling	Rounds up to a whole number: Ceiling(2.5) = 3, Ceiling(-4.37) = -4.	Ceiling(Num)
Exp	e (2.71828…) raised to the power Num: Exp(1) = 2.71828.	Exp(Num)
Floor	Rounds down to a whole number: Floor(4.3) = 4, Floor(-5.4) = -6.	Floor(Num)
Ln	The natural logarithm (inverse of Exp); Num must be positive. Ln(Exp(4)) = 4.	Ln(Num)
Log10	The base-10 logarithm; Num must be positive.	Log10(Num)
Max	The larger of the two arguments: Max(4,9) = 9.	Max(Num1, Num2)
Min	The smaller of the two arguments: Min(4,9) = 4.	Min(Num1, Num2)
Round	Rounds to NumDigits decimal places; 0 rounds to an integer, negative rounds left of the decimal: Round(3.45, 1) = 3.5, Round(11.5,-1) = 10.	Round(Num, NumDigits)
Sqrt	The positive square root; Num must be positive.	Sqrt(Num)
Trunc	Rounds toward zero to NumDigits decimal places: Trunc(9.765,2) = 9.76, Trunc(-9.765,2) = -9.76.	Trunc(Num, NumDigits)

Statistical functions

These return random values from distributions — the heart of realistic durations and decisions.

Function	Description	Syntax
BernoulliDist	Returns 1 or 0; the argument is how often 1 comes back. BernoulliDist(0.7) returns 1 about 70% of the time.	BernoulliDist(Probability)
BetaDist	The cumulative Beta probability density between Min and Max; commonly used to study variation in a percentage across samples.	BetaDist(A,B,Min,Max)
Between	A uniformly distributed number between Min and Max, both inclusive — every value equally likely.	Between(Min,Max)
BetweenNorm	A normally distributed value between Min and Max — mean and deviation are derived from the bounds, and the result always stays inside them. BetweenNorm(10,20) is usually near 15, seldom 10 or 20.	BetweenNorm(Min,Max)
BinomDist	Models drawing from a pool of N items, each drawn successfully with the given probability.	BinomDist(N,Probability)
CustomDist	A custom distribution over intervals between 0 and 100. The first parameter is the value of the last interval; the rest are pairs of interval upper bound and value. CustomDist(5, 25, 20, 75, 10): 0–25 → 20, 25–75 → 10, 75–100 → 5.	CustomDist(LastValue, Bound1, Value1, …BoundN, ValueN)
ErlangDist	Random values where N is the mean and B the variance; both must be greater than zero and N is an integer. A subset of the Gamma distribution.	ErlangDist(N,B)
ExponDist	A value from the Exponential distribution with the given Rate — values cluster near the rate, with occasional large spikes. Computed as -ln(1-x) / Rate for a uniform random x.	ExponDist(Rate)
GammaDist	Random values from the Gamma distribution with shape parameters A and B.	GammaDist(A,B)
LogNormDist	The logarithmic normal distribution; parameters are the mean and the variance (deviation squared).	LogNormDist(Mean,Variance)
NormDist	A normal random variable with the given mean and standard deviation.	NormDist(Mean,Deviation)
NormSDist	A standard normal random variable — mean 0, standard deviation 1. Takes no arguments.	NormSDist()
PercentTrue	Returns true Num% of the time: PercentTrue(95) is true 95% of the time.	PercentTrue(Num)
PercentFalse	Returns false Num% of the time: PercentFalse(95) is false 95% of the time.	PercentFalse(Num)
PoissonDist	The limiting form of the Binomial distribution; exponential interarrival times are the same as Poisson arrivals.	PoissonDist(Mean)
ProportionalDist	Returns the index i with probability Num(i) divided by the sum of all arguments (up to 12 arguments, all ≥ 0); returns -1 when the sum is 0.	ProportionalDist(Num0,Num1,…)
Random	A uniform random real number between 0 and 1.	Random()
TriangleDist	A triangle-shaped distribution: Min and Max bound the result, Mode is the most likely value.	TriangleDist(Min,Max,Mode)
WeibullDist	The Weibull distribution with parameters A and B (both greater than 0); typically used for reliability analysis.	WeibullDist(A,B)

String functions

Function	Description	Syntax
Compare	CaseCase A single instance of a process — for example, one customer order, invoice, or support ticket. An event log groups events by case ID.-sensitive comparison: -1 when String1 is less than String2, 0 when equal, 1 when greater.	Compare(String1, String2)
CompareNoCase	The case-insensitive version of Compare.	CompareNoCase(String1, String2)
Concat	Joins two strings: Concat("Hello", "World") = "HelloWorld".	Concat(String1, String2)
CropLeft	Searches left to right for the single character CropString and deletes everything up to and including it; returns String unchanged when not found.	CropLeft(String, CropString)
CropRight	Searches right to left for the single character CropString and deletes from it to the end; returns String unchanged when not found.	CropRight(String, CropString)
Delete	Deletes at most Count characters starting at Index.	Delete(String, Index[, Count = 1])
Find	CaseCase A single instance of a process — for example, one customer order, invoice, or support ticket. An event log groups events by case ID.-sensitive search for SearchString starting at Index; returns the index found, or -1.	Find(String, SearchString[, Index = 0])
FindNoCase	The case-insensitive version of Find.	FindNoCase(String, SearchString[, Index = 0])
FindOneOf	Returns the index of the first character of String that also appears in FindString, or -1.	FindOneOf(String, FindString)
GetLength	The length of String.	GetLength(String)
Insert	Inserts InsertionString into String at Index.	Insert(String, Index, InsertionString)
LeftCount	The leftmost Count characters; the whole string when Count exceeds its length.	LeftCount(String, Count)
LeftIndexString	The characters left of the first occurrence of IndexString; String unchanged when not found.	LeftIndexString(String, IndexString)
MakeLower	Converts to lowercase.	MakeLower(String)
MakeUpper	Converts to uppercase.	MakeUpper(String)
MakeReverse	Reverses the character order.	MakeReverse(String)
MidIndex	At most Count characters starting at Index.	MidIndex(String, Index[, Count])
MidIndexString	At most Count characters starting at the first occurrence of IndexString; the null string when not found.	MidIndexString(String, IndexString[, Count])
Replace	CaseCase A single instance of a process — for example, one customer order, invoice, or support ticket. An event log groups events by case ID.-sensitive replacement of every OldString with NewString.	Replace(String, OldString, NewString)
ReplaceNoCase	The case-insensitive version of Replace.	ReplaceNoCase(String, OldString, NewString)
ReverseFind	Searches right to left for the single character SearchString; returns its index, or -1.	ReverseFind(String, SearchString)
RightCount	The rightmost Count characters.	RightCount(String, Count)
RightIndexString	The characters right of the first occurrence of IndexString; the null string when not found.	RightIndexString(String, IndexString)
SetAt	Overwrites String with SetString starting at Index; the result can be longer than String.	SetAt(String, Index, SetString)
SpanExcluding	The leading characters of String up to (but excluding) the first character found in SpanString; String unchanged when none is found.	SpanExcluding(String, SpanString)
SpanIncluding	The leading characters of String that appear in SpanString, stopping at the first that doesn't; the null string when the first character already doesn't.	SpanIncluding(String, SpanString)
ToNumber	Converts a string to a number; leading and trailing spaces are ignored and the null string becomes 0. Numbers pass through unchanged.	ToNumber(Value)
TrimLeft	Removes leading spaces.	TrimLeft(String)
TrimRight	Removes trailing spaces.	TrimRight(String)
ValueToString	Converts a value to a string; strings pass through unchanged.	ValueToString(Value)

Notes / constraints

• The autocomplete list is the authoritative function catalog for your release: anything it offers is available, its tooltips match the descriptions above, and typing inside a function's parentheses shows each parameter's name and position.
• Scoring function expressions evaluate after the run ends, so they can additionally read the run's statistics through the Statistics scope.

Related

• Simulation properties — variables, custom functions, scenarios
• Simulation shape properties — where expressions are used
• Use table variables