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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#

operatorsymbolexample
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
betweenbetween _ 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
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