bool-parser-go

An Expression Parser for Go

The library can help parse complex and nested boolean and arithmetic expressions. The expressions are in SQL-like syntax, where you can use boolean operators and parentheses to combine individual expressions.

An expression can be as simple as name = 'Sidhant'. A Complex expression is formed by combining these small expressions by logical operators and giving precedence using parenthesis

Examples

Textual Equality

Format: ${attributeName} = ${value}

Example: name = john

Numeric Comparisons

Format: ${attributeName} ${operator} ${value}

Example: price > 12.99

The ${value} must be numeric. Supported operators are <, <=, =, !=, >= and >, with the same semantics as in virtually all programming languages.

Numeric Range

Format: ${attributeName} ${lowerBound} TO ${upperBound}

Example: price 5.99 TO 100

${lowerBound} and ${upperBound} must be numeric. Both are inclusive.

Boolean operators

Example:

price < 10 AND (category:Book OR NOT category:Ebook)

Individual filters can be combined via boolean operators. The following operators are supported:

• OR: must match any of the combined conditions (disjunction)
• AND: must match all of the combined conditions (conjunction)
• NOT: negate a filter

Parentheses, ( and ), can be used for grouping.

Usage Notes

• String must be enclosed either in single or double quotes.
• Variables substitution is supported by passing the name of the variable without the quotes.
• Phrases that includes quotes, like content = "It's a wonderful day"
• Phrases that includes quotes, like attribute = 'She said "Hello World"'
• For nested keys in data map you can use the dot notation, like person.age

Usage

go get github.com/sidhant92/bool-parser-go

Code

package main

import (
	"fmt"
	"github.com/sidhant92/bool-parser-go/pkg/application"
	"github.com/sidhant92/bool-parser-go/pkg/parser"
)

func main() {
	antlrParser := parser.New()
	evaluator := application.NewBooleanExpressionEvaluator(antlrParser)
	data := map[string]interface{}{
		"age": 25,
	}
	res, err := evaluator.Evaluate("age > 20", data)

	if err == nil {
		// true
		fmt.Println(res)
	}
}

Applications

Boolean Expression Evaluator

The library can be used to evaluate a boolean expression.

The following Data Types are supported:

1. String
2. Integer
3. Long
4. Decimal
5. Boolean
6. Semantic Version

Usage examples:

Simple Numerical Comparison

data := map[string]interface{}{
	"age": 26,
}
res, err := evaluator.Evaluate("age >= 27", data)
assert.Nil(t, err)
assert.False(t, res)

Boolean Comparison

data := map[string]interface{}{
	"age":  25,
	"name": "sid",
}
res, err := evaluator.Evaluate("name = 'sid' AND age = 25", data)
assert.Nil(t, err)
assert.True(t, res)

Nested Boolean Comparison

data := map[string]interface{}{
	"age":  25,
	"name": "sid",
	"num":  45,
}
res, err := evaluator.Evaluate("name = 'sid' AND (age = 25 OR num = 44)", data)
assert.Nil(t, err)
assert.True(t, res)

Semantic Version Comparison

data := map[string]interface{}{
	"app_version": "1.5.9",
}
res, err := evaluator.Evaluate("app_version < 1.5.10", data)
assert.Nil(t, err)
assert.True(t, res)

The return type is res, err. Failure means that parsing has failed and any fallback can be used.

For a complete list of examples please check out the test file

Arithmetic Expression Evaluator

The library can be used to evaluate a arithmetic expression. It supports both numbers and variables which will be substituted from the passed data. The passed variables can also be passed using the dot notation to access nested fields from the input data.

The following Data Types are supported:

1. String
2. Integer
3. Long
4. Decimal

The following Operators are supported:

1. Addition (+)
2. Subtraction (-)
3. Multiplication (*)
4. Division (/)
5. Modulus (%)
6. Exponent (^)

The following functions are supported:

1. Minimum (min)
2. Maximum (max)
3. Average (avg)
4. Sum (sum)
5. Mean (mean)
6. Mode (mode)
7. Median (median)
8. Integer (int) - converts the input to integer
9. Length (len) - Returns length of the give array

Syntax For using functions Format: ${FunctionIdentifier} (item1, item2...)

Example: min (1,2,3) or with variable substitution min (a,b,c)

Usage examples:

Simple Addition Operation

var evaluator = NewArithmeticExpressionEvaluator(parser.New())
data := map[string]interface{}{
	"a": 10,
}
res, err := evaluator.Evaluate("a + 5", data)
assert.Nil(t, err)
assert.Equal(t, res, 15)

Complex Arithmetic Operation

var evaluator = NewArithmeticExpressionEvaluator(parser.New())
data := map[string]interface{}{
	"a": 10,
}
res, err := evaluator.Evaluate("((5 * 2) + a) * 2 + (1 + 3 * (a / 2))", data)
assert.Nil(t, err)
assert.Equal(t, res, 56)

Function Usage

var evaluator = NewArithmeticExpressionEvaluator(parser.New())
data := map[string]interface{}{
		"a": 10,
	}
res, err := evaluator.Evaluate("min (1,2,3)", data)
assert.Nil(t, err)
assert.Equal(t, res, 1)

For a complete list of examples please check out the test file