Expr is a handy expression parser.
It supports writing logical expressions as strings and evaluating them against data records (for example, rows from a CSV file or database query).
Measures for Justice developed Expr to provide a simple format for data researchers and developers to collaborate on data matching logic without needing to tie it to the language of a specific target engine (such as R or Java).
Expr is released under the Apache License 2.0.
Expr is deployed to Maven Central with GAV io.mfj:expr.
Expr requires Java 11+.
* Expression : Term ( Conjunction Term )*
* Term : Statement | Not | Parens
* Parens : '(' Expression ')'
* Not : 'not' Whitespace* '(' Expression ')'
* Statement : Value Operator Value ( Operator Value )?
* Value : MathStatement | VariableName | LiteralValue | List
* MathStatement : Value MathOperator Value
* Conjunction : Whitespace+ ( 'and' | 'or' ) Whitespace+
* Operator : '!=' | '<>' | '>=' | '<=' | '>' | '<' | '=~' | '=' | 'in' | '!in' | 'contains' | '!contains'
* MathOperator : '+' | '-'
* Whitespace : ' ' | '\t' | '\n'
* LiteralValue : Null | Integer | Decimal | String | Regex | Boolean | Date | Time | DateTime
* Null : 'null'
* String : '"' TextOrEmpty{" escaped by \} '"'
* Regex : '/' TextOrEmpty{/ escaped by \} '/'
* Number : '-'? Digit+ ( '.' Digit+ )?
* Boolean : 'true' | 'false'
* Date : "d'" ISO_8601_Date "'"
* Time : "t'" ISO_8601_Time "'"
* DateTime : "dt'" ISO_8601_DateTime "'"
* VariableName : /[a-zA-Z_][a-zA-Z0-9_]*/
* List: '[' ( Value ( ',' Value )* ','? )? ']'
1 < myVar <= 6 is valid. It means 1 < myVar and myVar <= 6.
It is awesome.
- String -
kotlin.String - Regex -
kotlin.text.Regex - Number -
java.math.BigDecimal - Date -
java.time.LocalDate - Time -
java.time.LocalTime - DateTime -
java.time.LocalDateTime - Boolean -
kotlin.Boolean - List -
java.util.List
Expr's version is of the format major.minor.build.
The major number is incremented for breaking changes or major new features.
The minor number is incremented for minor new features.
The build number is generated by Measures for Justice's private CI tool. It is incremented for each build, regardless of the major and minor numbers (it does not reset to zero when minor or major numbers are increased).