Operators, literals and structures

Values

Decimal

double

A decimal number. Written with a point, never a comma, whatever the display locale.

Returns double: The number as written.

Examples

2.5 → 2.5
1.5e3 → 1500.0

False

false

The boolean a comparison yields when it does not hold. Written bare and lower case, never quoted.

Returns boolean: False.

Examples

false → false
PUMP_ON == false → false

Null

null

The absence of a value. Use it as the fallback of a lookup, and read it back with nvl.

Returns any: Nothing - null itself.

Examples

null → null
nvl(null, 0) → 0

Number

integer

A whole number written straight into the script. It is a 32-bit integer: one above 2147483647 does not compile, so write a larger value with a decimal point.

Returns int: The number as written.

Examples

42 → 42
COUNT + 1 → 4.0
2147483647 → 2147483647

Text

string

A fixed piece of text, in double quotes. Quotes and backslashes inside it are escaped with a backslash.

Returns string: The text as written.

Examples

"P-101" → "P-101"
"Pump \"A\" stopped" → "Pump \"A\" stopped"
"Tank " + TAG → "Tank P-101"

True

true

The boolean a comparison yields when it holds. Written bare and lower case, never quoted.

Returns boolean: True.

Examples

true → true
not(true) → false

Operators

Add

+ · left: any + right: any...

Adds numbers. When the left value is text it joins the others on as text instead: "a" + 1 gives "a1", while 1 + "a" fails.

Parameters

Name	Type	Description
left	any	The value on the left of the operator.
right	any (1 or more)	A further value to add. The operator chains, so a + b + c is one expression.

Returns any: The sum, or the joined text.

Examples

LEVEL + 7.5 → 50.0
COUNT + 1 → 4.0
"Tank " + TAG → "Tank P-101"
TAG + 1 → "P-1011"
1 + "a" → error

And (short-circuit)

&& · left: boolean && right: boolean...

True only when both sides are true. The right side is only evaluated if the left one holds, so it can guard a condition that is only valid once the left one holds.

Parameters

Name	Type	Description
left	boolean	The condition on the left of the operator.
right	boolean (1 or more)	A further condition. The operator chains, so a && b && c is one expression.

Returns boolean: True when both sides are true.

Examples

PUMP_ON && LEVEL > 40 → true
false && NEVER_WRITTEN > 0 → false

Divide

/ · left: double / right: double...

Divides the left value by the right one. Dividing by zero yields an infinite value rather than failing - guard it with ivl. When the left value is text it joins the others on as text instead, as + does.

Parameters

Name	Type	Description
left	double	The value to divide.
right	double (1 or more)	A further value to divide by. Chains left to right, so a / b / c divides twice.

Returns double: The quotient.

Examples

LEVEL / 2 → 21.25
1 / 0 → Infinity

Multiply

* · left: double * right: double...

Multiplies numbers. When the left value is text it joins the others on as text instead, as + does: "ab" * 3 gives "ab3".

Parameters

Name	Type	Description
left	double	The value on the left of the operator.
right	double (1 or more)	A further factor. The operator chains, so a * b * c is one expression.

Returns double: The product.

Examples

COUNT * 2 → 6.0
LEVEL * 1.8 + 32 → 108.5

Negate

- · -value: double

Flips the sign of a number and keeps its kind: a whole number stays whole and a decimal stays decimal. Anything that is not a number gives null. This is the unary minus, distinct from the subtraction operator that takes two values.

Parameters

Name	Type	Description
value	double	The number whose sign is flipped.

Returns double: The value with the opposite sign, of the same kind.

Examples

-LEVEL → -42.5
-COUNT → -3
-(LEVEL - 50) → 7.5

Or (short-circuit)

|| · left: boolean || right: boolean...

True when either side is true. The right side is only evaluated if the left one is false.

Parameters

Name	Type	Description
left	boolean	The condition on the left of the operator.
right	boolean (1 or more)	A further condition. The operator chains, so a || b || c is one expression.

Returns boolean: True when either side is true.

Examples

PUMP_ON || LEVEL > 90 → true
true || NEVER_WRITTEN > 0 → true

Power

^ · left: double ^ right: double...

Raises the left value to the power of the right one.

Parameters

Name	Type	Description
left	double	The base.
right	double (1 or more)	A further exponent. Chains in the order written, so a ^ b ^ c raises twice.

Returns double: The power.

Examples

2 ^ 3 → 8.0
2 ^ 3 ^ 2 → 64.0
COUNT ^ 2 → 9.0

Subtract

- · left: double - right: double...

Subtracts the right value from the left one. Distinct from the unary minus, which takes a single value.

Parameters

Name	Type	Description
left	double	The value to subtract from.
right	double (1 or more)	A further value to subtract. Chains left to right, so a - b - c subtracts both.

Returns double: The difference.

Examples

LEVEL - 2.5 → 40.0
100 - LEVEL - 7.5 → 50.0

Comparisons

Equals

== · left: any == right: any

True when both values match. Always written doubled: a single = is not a comparison. Comparing a number with text is an error.

Parameters

Name	Type	Description
left	any	The value on the left of the comparison.
right	any	The value on the right of the comparison.

Returns boolean: True when the comparison holds.

Examples

COUNT == 3 → true
TAG == "P-101" → true
1.0 == 1 → true

Greater than

> · left: any > right: any

True when the left value sorts after the right one. Comparing a number with text is an error.

Parameters

Name	Type	Description
left	any	The value on the left of the comparison.
right	any	The value on the right of the comparison.

Returns boolean: True when the comparison holds.

Examples

LEVEL > 40 → true
TAG > "P-100" → true

Greater than or equal

>= · left: any >= right: any

True when the left value sorts after the right one, or matches it. Comparing a number with text is an error.

Parameters

Name	Type	Description
left	any	The value on the left of the comparison.
right	any	The value on the right of the comparison.

Returns boolean: True when the comparison holds.

Examples

COUNT >= 3 → true

Less than

< · left: any < right: any

True when the left value sorts before the right one. Comparing a number with text is an error.

Parameters

Name	Type	Description
left	any	The value on the left of the comparison.
right	any	The value on the right of the comparison.

Returns boolean: True when the comparison holds.

Examples

LEVEL < SETPOINTS.low → false
SETPOINTS.low < LEVEL < SETPOINTS.high → true

Less than or equal

<= · left: any <= right: any

True when the left value sorts before the right one, or matches it. Comparing a number with text is an error.

Parameters

Name	Type	Description
left	any	The value on the left of the comparison.
right	any	The value on the right of the comparison.

Returns boolean: True when the comparison holds.

Examples

LEVEL <= 42.5 → true

Not equal

<> · left: any <> right: any

True when the two values differ. The spelling to prefer in new scripts. Comparing a number with text is an error.

Parameters

Name	Type	Description
left	any	The value on the left of the comparison.
right	any	The value on the right of the comparison.

Returns boolean: True when the comparison holds.

Examples

TAG <> "P-102" → true

Not equal (C style)

!= · left: any != right: any

True when the two values differ. Accepted as a synonym of <> so scripts written in C style keep working. Comparing a number with text is an error.

Parameters

Name	Type	Description
left	any	The value on the left of the comparison.
right	any	The value on the right of the comparison.

Returns boolean: True when the comparison holds.

Examples

COUNT != 3 → false

Structures

Field

. · record: object.field: name

Reads one named field out of a record - a control function's state, a database row, an inline object. The name is written bare, never in quotes, and a field the record does not hold is an error rather than a null.

Parameters

Name	Type	Description
record	object	The record the field is read from.
field	name	The name of the field to read.

Returns any: Whatever that field holds.

Examples

SETPOINTS.high → 90
{level: LEVEL, alarm: false}.level → 42.5

Item at

[] · list: [][position: int]

Reads one item out of a list by its position, counting from zero. Ask length how many there are before reaching past the end.

Parameters

Name	Type	Description
list	[]	The list the item is read from.
position	int	Which item to read, counting from zero.

Returns any: The item at that position.

Examples

REGISTERS[2] → 65535
[10, 20, 30][0] → 10
REGISTERS[4] → error

List

array

An ordered list written inline, [a, b, c]. Read an item back by index, and count them with length.

Returns []: The list, holding its items in order.

Examples

[LEVEL, COUNT, TAG] → [42.5, 3, "P-101"]
[] → []
[1, [2, 3]] → [1, [2, 3]]

Object

object

A record of named fields written inline, {key: value}. This is how a control function's settings and state are built.

Returns object: The record, holding its named fields.

Examples

{level: LEVEL, alarm: LEVEL > 90} → {alarm: false, level: 42.5}
{} → {}
{low = 10, high = 90} → {high: 90, low: 10}

This page describes Amtiri Script 5.4.1 as shipped with Data Orchester engine 6.12.1 and Site 1.22.7.