Expressions

An expression can contain literals, operators and function calls.

Literal

A single value of one of the types.

null
21
"valid"

Path Expression

Access a value by its name/path. For example, a given variable from the input/context.

x + y

If the value is a context (or data object/POJO) then the inner values can be accessed by context.key.

x.y
// return 1 if x is {y: 1}

Also, directly on a context.

{x: 2}.x
// 2

{x: {y: "valid"}}.x
// {y: "valid"}

{x: {y: "valid"}}.x.y
// "valid"

Inside a context, the previous values can be accessed.

{
  a: 1,
  b: 2,
  c: a + b
}

If the name or path contains any special character (e.g. whitespace, dash, etc.) then the name needs to be wrapped into single backquotes/backtick `foo bar`.

`name with whitespace`.`name+operator`

Addition

• supported types: number, string, day-time-duration, year-month-duration

2 + 3
// 5

"foo" + "bar"
// "foobar"

duration("P1D") + duration("PT6H")
// duration("P1DT6H")

Subtraction

• supported types: number, time, date-time, day-time-duration, year-month-duration

5 - 3
// 2

time("10:30:00") - time("09:00:00")
// duration("PT1H30M")

time("10:30:00") - duration("PT1H")
// time("09:30:00")

Multiplication

• supported types: number, day-time-duration, year-month-duration

5 * 3
// 15

3 * duration("P2Y")
// duration("P6Y")

Division

• supported types: number, day-time-duration, year-month-duration

6 / 2
// 3

duration("P1Y") / 2
// duration("P6M")

duration("P1Y") / duration("P1M")
// 12

Exponentiation

• supported types: number

2 ** 3
// 8

Comparison

operator	symbol	example
equal to	=	x = "valid"
not equal to	!=	x != "valid"
less than	<	< 10
less than or equal	<=	<= 10
greater than	>	> 10
greater than or equal	>=	>= 10
between	between _ and _	x between 3 and 9

The operators less than, greater than, and between are only supported for:

• number
• date
• time
• date-time
• year-month-duration
• day-time-duration

Any value can be compared with null to check if it is equal to null, or if it exists. Comparing null to a value different from null results in false. It returns true if the value, or the context entry (e.g. the property of a variable) is null or doesn't exist. The built-in function is defined() can be used to differentiate between a value that is null and a value that doesn't exist.

null = null
// true

"foo" = null
// false

x = null
// true - if "x" is null or doesn't exist

x.y = null
// true - if "x" is null, "x" doesn't exist,
//           "y" is null, or "x" has no property "y"

Disjunction and Conjunction

Combine two boolean values.

true and true
// true

true and false
// false

true and null
// null

false and null
// false

true or false
// true

false or false
// false

true or null
// true

false or null
// null

If Expression

if (x < 5) then "low" else "high"

For Expressions

Iterate over a list and apply an expression (i.e. aka map). The result is again a list.

for x in [1,2] return x * 2
// [2,4]

Iterate over multiple lists.

for x in [1,2], y in [3,4] return x * y
// [3,4,6,8]

Iterate over a range - forward or backward.

for x in 1..3 return x * 2
// [2,4,6]

for x in 3..1 return x * 2
// [6,4,2]

The previous results of the iterator can be accessed by the variable partial.

for x in 1..5 return x + sum(partial)
// [1,3,7,15,31]

Some/Every Expression

Test if at least one element of the list satisfies the expression.

some x in [1,2,3] satisfies x > 2
// true

some x in [1,2,3] satisfies x > 3
// false

some x in [1,2], y in [2,3] satisfies x < y
// true

Test if all elements of the list satisfies the expression.

every x in [1,2,3] satisfies x >= 1
// true

every x in [1,2,3] satisfies x >= 2
// false

every x in [1,2], y in [2,3] satisfies x < y
// false

Filter Expression

Filter a list of elements by an expression. The expression can access the current element by item. The result is a list again.

[1,2,3,4][item > 2]
// [3,4]

An element of a list can be accessed by its index. The index starts at 1. A negative index starts at the end by -1.

[1,2,3,4][1]
// 1

[1,2,3,4][4]
// 4

[1,2,3,4][-1]
// 4

[1,2,3,4][-2]
// 3

[1,2,3,4][5]
// null

If the elements are contextes then the nested value of the current element can be accessed directly by its name.

[ {a: "foo", b: 5},  {a: "bar", b: 10} ][b > 7]
// {a : "bar", b: 10}

The nested values of a specific key can be extracted by .key.

[ {a : "foo", b: 5 }, {a: "bar", b: 10} ].a
// ["foo", "bar"]

Evaluate a Unary Tests

Evaluates a unary-tests expression with the given value.

x in (2..4)

x in < 3

Instance-Of Expression

Checks the type of the value.

"foo" instance of number
// false

"bar" instance of string
// true

Functions

Invoke a user-defined or built-in function by its name. The arguments can be passed positional or named.

add(1,2)
// or
add(x:1, y:2)

A function (body) can be defined using function(arguments) expression. For example, inside a context.

{
    add : function(x,y) x + y
}

Special Properties

Values of type date, time, date-time and duration have special properties to access their individual parts.

date("2017-03-10").year
date("2017-03-10").month
date("2017-03-10").day
date("2017-03-10").weekday

time("11:45:30+02:00").hour
time("11:45:30+02:00").minute
time("11:45:30+02:00").second
time("11:45:30+02:00").time offset

date and time("2017-03-10T11:45:30+02:00").year
date and time("2017-03-10T11:45:30+02:00").month
date and time("2017-03-10T11:45:30+02:00").day
date and time("2017-03-10T11:45:30+02:00").weekday
date and time("2017-03-10T11:45:30+02:00").hour
date and time("2017-03-10T11:45:30+02:00").minute
date and time("2017-03-10T11:45:30+02:00").second
date and time("2017-03-10T11:45:30+02:00").time offset
date and time("2017-03-10T11:45:30+02:00").timezone

duration("P2Y3M").years
duration("P2Y3M").months

duration("P1DT2H10M30S").days
duration("P1DT2H10M30S").hours
duration("P1DT2H10M30S").minutes
duration("P1DT2H10M30S").seconds