= Stream Evaluator Reference
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Stream evaluators are different the stream sources or stream decorators. Both
streaming sources and stream decorators return streams of tuples.

Stream evaluators are more like traditional functions that evaluates its parameters and
returns an result. That result can be a single value, array, map or other structure.

Stream evaluators can be nested to so that the output of evaluator becomes the input
for another evaluatore.

Stream evaluators can be called in different contexts. For example a stream evaluator
can be called on its own or it can be called within the context of a streaming expression.


== analyze

The `analyze` function analyzes text using a Lucene/Solr analyzer and returns a list of tokens
emitted by the analyzer. The `analyze` function can be called on its own or within the
`select` and `cartasianProduct` Streaming Expressions.

=== analyze Parameters

* `Field Name` | `Raw Text`: Either the field in a tuple or the raw text to be analyzed.
* `Analyzer field name`: The field name of the analyzer to use to analyze the text.

=== analyze Syntax

The expressions below show the various ways in which you can use the `analyze` evaluator.

[source,text]
----
analyze("hello world", analyzerField) // Analyze the raw text
select(expr, analyze(textField, analyzerField) as outField) // Analyze a text field within a select expression. This will annotate the tuples with output of the analyzer
cartesianProduct(expr, analyze(textField, analyzer) as outField) // Analyze a text field with a cartesianProduct expression. This will stream each token emitted by the analyzer in its own tuple.
----


== abs

The `abs` function will return the absolute value of the provided single parameter. The `abs` function will fail to execute if the value is non-numeric. If a null value is found then null will be returned as the result.

=== abs Parameters

* `Field Name | Raw Number | Number Evaluator`

=== abs Syntax

The expressions below show the various ways in which you can use the `abs` evaluator. Only one parameter is accepted. Returns a numeric value.

[source,text]
----
abs(1) // 1, not really a good use case for it
abs(-1) // 1, not really a good use case for it
abs(add(fieldA,fieldB)) // absolute value of fieldA + fieldB
abs(fieldA) // absolute value of fieldA
----

== add

The `add` function will take 2 or more numeric values and add them together. The `add` function will fail to execute if any of the values are non-numeric. If a null value is found then null will be returned as the result.

=== add Parameters

* `Field Name | Raw Number | Number Evaluator`
* `Field Name | Raw Number | Number Evaluator`
* `......`
* `Field Name | Raw Number | Number Evaluator`

=== add Syntax

The expressions below show the various ways in which you can use the `add` evaluator. The number and order of these parameters do not matter and is not limited except that at least two parameters are required. Returns a numeric value.

[source,text]
----
add(1,2,3,4) // 1 + 2 + 3 + 4 == 10
add(1,fieldA) // 1 + value of fieldA
add(fieldA,1.4) // value of fieldA + 1.4
add(fieldA,fieldB,fieldC) // value of fieldA + value of fieldB + value of fieldC
add(fieldA,div(fieldA,fieldB)) // value of fieldA + (value of fieldA / value of fieldB)
add(fieldA,if(gt(fieldA,fieldB),fieldA,fieldB)) // if fieldA > fieldB then fieldA + fieldA, else fieldA + fieldB
----

== div

The `div` function will take two numeric values and divide them. The function will fail to execute if any of the values are non-numeric or null, or the 2nd value is 0. Returns a numeric value.

=== div Parameters

* `Field Name | Raw Number | Number Evaluator`
* `Field Name | Raw Number | Number Evaluator`

=== div Syntax

The expressions below show the various ways in which you can use the `div` evaluator. The first value will be divided by the second and as such the second cannot be 0.

[source,text]
----
div(1,2) // 1 / 2
div(1,fieldA) // 1 / fieldA
div(fieldA,1.4) // fieldA / 1.4
div(fieldA,add(fieldA,fieldB)) // fieldA / (fieldA + fieldB)
----

== log

The `log` function will return the natural log of the provided single parameter. The `log` function will fail to execute if the value is non-numeric. If a null value is found, then null will be returned as the result.

=== log Parameters

* `Field Name | Raw Number | Number Evaluator`

=== log Syntax

The expressions below show the various ways in which you can use the `log` evaluator. Only one parameter is accepted. Returns a numeric value.

[source,text]
----
log(100)
log(add(fieldA,fieldB))
log(fieldA)
----

== mult

The `mult` function will take two or more numeric values and multiply them together. The `mult` function will fail to execute if any of the values are non-numeric. If a null value is found then null will be returned as the result.

=== mult Parameters

* `Field Name | Raw Number | Number Evaluator`
* `Field Name | Raw Number | Number Evaluator`
* `......`
* `Field Name | Raw Number | Number Evaluator`

=== mult Syntax

The expressions below show the various ways in which you can use the `mult` evaluator. The number and order of these parameters do not matter and is not limited except that at least two parameters are required. Returns a numeric value.

[source,text]
----
mult(1,2,3,4) // 1 * 2 * 3 * 4
mult(1,fieldA) // 1 * value of fieldA
mult(fieldA,1.4) // value of fieldA * 1.4
mult(fieldA,fieldB,fieldC) // value of fieldA * value of fieldB * value of fieldC
mult(fieldA,div(fieldA,fieldB)) // value of fieldA * (value of fieldA / value of fieldB)
mult(fieldA,if(gt(fieldA,fieldB),fieldA,fieldB)) // if fieldA > fieldB then fieldA * fieldA, else fieldA * fieldB
----

== sub

The `sub` function will take 2 or more numeric values and subtract them, from left to right. The sub function will fail to execute if any of the values are non-numeric. If a null value is found then null will be returned as the result.

=== sub Parameters

* `Field Name | Raw Number | Number Evaluator`
* `Field Name | Raw Number | Number Evaluator`
* `......`
* `Field Name | Raw Number | Number Evaluator`

=== sub Syntax

The expressions below show the various ways in which you can use the `sub` evaluator. The number of these parameters does not matter and is not limited except that at least two parameters are required. Returns a numeric value.

[source,text]
----
sub(1,2,3,4) // 1 - 2 - 3 - 4
sub(1,fieldA) // 1 - value of fieldA
sub(fieldA,1.4) // value of fieldA - 1.4
sub(fieldA,fieldB,fieldC) // value of fieldA - value of fieldB - value of fieldC
sub(fieldA,div(fieldA,fieldB)) // value of fieldA - (value of fieldA / value of fieldB)
if(gt(fieldA,fieldB),sub(fieldA,fieldB),sub(fieldB,fieldA)) // if fieldA > fieldB then fieldA - fieldB, else fieldB - field
----

== pow
//TODO

== mod
//TODO

=== ceil
//TODO

== floor
//TODO

== sin
//TODO

== asin
//TODO

== sinh
//TODO

== cos
//TODO

== acos
//TODO

== atan
//TODO

== round
//TODO

== sqrt
//TODO

== cbrt

== and

The `and` function will return the logical AND of at least 2 boolean parameters. The function will fail to execute if any parameters are non-boolean or null. Returns a boolean value.

=== and Parameters

* `Field Name | Raw Boolean | Boolean Evaluator`
* `Field Name | Raw Boolean | Boolean Evaluator`
* `......`
* `Field Name | Raw Boolean | Boolean Evaluator`

=== and Syntax

The expressions below show the various ways in which you can use the `and` evaluator. At least two parameters are required, but there is no limit to how many you can use.

[source,text]
----
and(true,fieldA) // true && fieldA
and(fieldA,fieldB) // fieldA && fieldB
and(or(fieldA,fieldB),fieldC) // (fieldA || fieldB) && fieldC
and(fieldA,fieldB,fieldC,or(fieldD,fieldE),fieldF)
----

== eq

The `eq` function will return whether all the parameters are equal, as per Java's standard `equals(...)` function. The function accepts parameters of any type, but will fail to execute if all the parameters are not of the same type. That is, all are Boolean, all are String, all are Numeric. If any any parameters are null and there is at least one parameter that is not null then false will be returned. Returns a boolean value.

=== eq Parameters

* `Field Name | Raw Value | Evaluator`
* `Field Name | Raw Value | Evaluator`
* `......`
* `Field Name | Raw Value | Evaluator`

=== eq Syntax

The expressions below show the various ways in which you can use the `eq` evaluator.

[source,text]
----
eq(1,2) // 1 == 2
eq(1,fieldA) // 1 == fieldA
eq(fieldA,val(foo)) fieldA == "foo"
eq(add(fieldA,fieldB),6) // fieldA + fieldB == 6
----

== eor

The `eor` function will return the logical exclusive or of at least two boolean parameters. The function will fail to execute if any parameters are non-boolean or null. Returns a boolean value.

=== eor Parameters

* `Field Name | Raw Boolean | Boolean Evaluator`
* `Field Name | Raw Boolean | Boolean Evaluator`
* `......`
* `Field Name | Raw Boolean | Boolean Evaluator`

=== eor Syntax

The expressions below show the various ways in which you can use the `eor` evaluator. At least two parameters are required, but there is no limit to how many you can use.

[source,text]
----
eor(true,fieldA) // true iff fieldA is false
eor(fieldA,fieldB) // true iff either fieldA or fieldB is true but not both
eor(eq(fieldA,fieldB),eq(fieldC,fieldD)) // true iff either fieldA == fieldB or fieldC == fieldD but not both
----

== gteq

The `gteq` function will return whether the first parameter is greater than or equal to the second parameter. The function accepts numeric and string parameters, but will fail to execute if all the parameters are not of the same type. That is, all are String or all are Numeric. If any any parameters are null then an error will be raised. Returns a boolean value.

=== gteq Parameters

* `Field Name | Raw Value | Evaluator`
* `Field Name | Raw Value | Evaluator`

=== gteq Syntax

The expressions below show the various ways in which you can use the `gteq` evaluator.

[source,text]
----
gteq(1,2) // 1 >= 2
gteq(1,fieldA) // 1 >= fieldA
gteq(fieldA,val(foo)) fieldA >= "foo"
gteq(add(fieldA,fieldB),6) // fieldA + fieldB >= 6
----

== gt

The `gt` function will return whether the first parameter is greater than the second parameter. The function accepts numeric or string parameters, but will fail to execute if all the parameters are not of the same type. That is, all are String or all are Numeric. If any any parameters are null then an error will be raised. Returns a boolean value.

=== gt Parameters

* `Field Name | Raw Value | Evaluator`
* `Field Name | Raw Value | Evaluator`

=== gt Syntax

The expressions below show the various ways in which you can use the `gt` evaluator.

[source,text]
----
gt(1,2) // 1 > 2
gt(1,fieldA) // 1 > fieldA
gt(fieldA,val(foo)) fieldA > "foo"
gt(add(fieldA,fieldB),6) // fieldA + fieldB > 6
----

== if

The `if` function works like a standard conditional if/then statement. If the first parameter is true, then the second parameter will be returned, else the third parameter will be returned. The function accepts a boolean as the first parameter and anything as the second and third parameters. An error will occur if the first parameter is not a boolean or is null.

=== if Parameters

* `Field Name | Raw Value | Boolean Evaluator`
* `Field Name | Raw Value | Evaluator`
* `Field Name | Raw Value | Evaluator`

=== if Syntax

The expressions below show the various ways in which you can use the `if` evaluator.

[source,text]
----
if(fieldA,fieldB,fieldC) // if fieldA is true then fieldB else fieldC
if(gt(fieldA,5), fieldA, 5) // if fieldA > 5 then fieldA else 5
if(eq(fieldB,null), null, div(fieldA,fieldB)) // if fieldB is null then null else fieldA / fieldB
----

== lteq

The `lteq` function will return whether the first parameter is less than or equal to the second parameter. The function accepts numeric and string parameters, but will fail to execute if all the parameters are not of the same type. That is, all are String or all are Numeric. If any any parameters are null then an error will be raised. Returns a boolean value.

=== lteq Parameters

* `Field Name | Raw Value | Evaluator`
* `Field Name | Raw Value | Evaluator`

=== lteq Syntax

The expressions below show the various ways in which you can use the `lteq` evaluator.

[source,text]
----
lteq(1,2) // 1 <= 2
lteq(1,fieldA) // 1 <= fieldA
lteq(fieldA,val(foo)) fieldA <= "foo"
lteq(add(fieldA,fieldB),6) // fieldA + fieldB <= 6
----

== lt

The `lt` function will return whether the first parameter is less than the second parameter. The function accepts numeric or string parameters, but will fail to execute if all the parameters are not of the same type. That is, all are String or all are Numeric. If any any parameters are null then an error will be raised. Returns a boolean value.

=== lt Parameters

* `Field Name | Raw Value | Evaluator`
* `Field Name | Raw Value | Evaluator`

=== lt Syntax

The expressions below show the various ways in which you can use the `lt` evaluator.

[source,text]
----
lt(1,2) // 1 < 2
lt(1,fieldA) // 1 < fieldA
lt(fieldA,val(foo)) fieldA < "foo"
lt(add(fieldA,fieldB),6) // fieldA + fieldB < 6
----

== not

The `not` function will return the logical NOT of a single boolean parameter. The function will fail to execute if the parameter is non-boolean or null. Returns a boolean value.

=== not Parameters

* `Field Name | Raw Boolean | Boolean Evaluator`

=== not Syntax

The expressions below show the various ways in which you can use the `not` evaluator. Only one parameter is allowed.

[source,text]
----
not(true) // false
not(fieldA) // true if fieldA is false else false
not(eq(fieldA,fieldB)) // true if fieldA != fieldB
----

== or

The `or` function will return the logical OR of at least 2 boolean parameters. The function will fail to execute if any parameters are non-boolean or null. Returns a boolean value.

=== or Parameters

* `Field Name | Raw Boolean | Boolean Evaluator`
* `Field Name | Raw Boolean | Boolean Evaluator`
* `......`
* `Field Name | Raw Boolean | Boolean Evaluator`

=== or Syntax

The expressions below show the various ways in which you can use the `or` evaluator. At least two parameters are required, but there is no limit to how many you can use.

[source,text]
----
or(true,fieldA) // true || fieldA
or(fieldA,fieldB) // fieldA || fieldB
or(and(fieldA,fieldB),fieldC) // (fieldA && fieldB) || fieldC
or(fieldA,fieldB,fieldC,and(fieldD,fieldE),fieldF)
----

== raw

The `raw` function will return whatever raw value is the parameter. This is useful for cases where you want to use a string as part of another evaluator.

=== raw Parameters

* `Raw Value`

=== raw Syntax

The expressions below show the various ways in which you can use the `raw` evaluator. Whatever is inside will be returned as-is. Internal evaluators are considered strings and are not evaluated.

[source,text]
----
raw(foo) // "foo"
raw(count(*)) // "count(*)"
raw(45) // 45
raw(true) // "true" (note: this returns the string "true" and not the boolean true)
eq(raw(fieldA), fieldA) // true if the value of fieldA equals the string "fieldA"
----

