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Predicate
=========
Predicate package used to create interpreted mini languages with Go syntax - mostly to define
various predicates for configuration, e.g.
```
Latency() > 40 || ErrorRate() > 0.5.
```
Here's an example of fully functional predicate language to deal with division remainders:
```go
// takes number and returns true or false
type numberPredicate func(v int) bool
// Converts one number to another
type numberMapper func(v int) int
// Function that creates predicate to test if the remainder is 0
func divisibleBy(divisor int) numberPredicate {
return func(v int) bool {
return v%divisor == 0
}
}
// Function - logical operator AND that combines predicates
func numberAND(a, b numberPredicate) numberPredicate {
return func(v int) bool {
return a(v) && b(v)
}
}
func main(){
// Create a new parser and define the supported operators and methods
p, err := NewParser(Def{
Operators: Operators{
AND: numberAND,
},
Functions: map[string]interface{}{
"DivisibleBy": divisibleBy,
},
})
pr, err := p.Parse("DivisibleBy(2) && DivisibleBy(3)")
if err == nil {
fmt.Fatalf("Error: %v", err)
}
pr.(numberPredicate)(2) // false
pr.(numberPredicate)(3) // false
pr.(numberPredicate)(6) // true
}
```
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