README
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Binary Expression Tree
Package exp implements a binary expression tree which can be used to evaluate arbitrary binary expressions. You can use this package to build your own expressions however a few expressions are provided out of the box.
Installation
$ go get github.com/alexkappa/exp
Usage
conjunction := And(True, True, True)
disjunction := Or(True, False)
negation := Not(False)
complex := Or(And(conjunction, disjunction), negation)
fmt.Printf("%t\n", complex.Eval(p)) // true
Documentation
API documentation is available at godoc.
Documentation
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Overview ¶
Package exp implements a binary expression tree which can be used to evaluate arbitrary binary expressions. You can use this package to build your own expressions however a few expressions are provided out of the box.
Example ¶
conjunction := And(True, True, True)
disjunction := Or(True, False)
negation := Not(False)
complex := Or(And(conjunction, disjunction), negation)
fmt.Printf("%t\n", complex.Eval(nil))
Output: true
Example (URL) ¶
writer := httptest.NewRecorder()
request, _ := http.NewRequest("GET", "http://example.com?event=signup&date=2014-10-03&basket_value=199.90&referrer=https://google.com", nil)
handler := func(w http.ResponseWriter, r *http.Request) {
exp := And(
Match("event", "signup"),
Before("date", time.Now()),
GreaterThan("basket_value", 99.99),
Contains("referrer", "google.com"))
if exp.Eval(r.URL.Query()) {
fmt.Fprintf(w, "Expression evaluates")
}
}
handler(writer, request)
fmt.Println(writer.Body.String())
Output: Expression evaluates
Index ¶
- Variables
- func DateFormat(f string) string
- type Bool
- type Exp
- func After(key string, date time.Time) Exp
- func And(t ...Exp) Exp
- func Before(key string, date time.Time) Exp
- func Contains(key, substr string) Exp
- func ContainsAny(key, chars string) Exp
- func ContainsRune(key string, r rune) Exp
- func Count(key, sep string, count int) Exp
- func Day(key string, day int) Exp
- func Eq(k string, v float64) Exp
- func Equal(k string, v float64) Exp
- func EqualFold(key, s string) Exp
- func GreaterOrEqual(k string, v float64) Exp
- func GreaterThan(k string, v float64) Exp
- func Gt(k string, v float64) Exp
- func Gte(k string, v float64) Exp
- func Len(key string, length int) Exp
- func LessOrEqual(k string, v float64) Exp
- func LessThan(k string, v float64) Exp
- func Lt(k string, v float64) Exp
- func Lte(k string, v float64) Exp
- func Match(key, str string) Exp
- func MatchAny(key string, strs ...string) Exp
- func Month(key string, month time.Month) Exp
- func Neq(k string, v float64) Exp
- func Not(t Exp) Exp
- func NotEqual(k string, v float64) Exp
- func On(key string, date time.Time) Exp
- func Or(t ...Exp) Exp
- func Weekday(key string, weekday time.Weekday) Exp
- func Year(key string, year int) Exp
- type Map
- type Params
Examples ¶
Constants ¶
This section is empty.
Variables ¶
var ( // True is an expression that always evaluates to true. True = Bool(true) // False is an expression that always evaluates to false. False = Bool(false) )
Functions ¶
func DateFormat ¶
DateFormat changes the date format used to parse dates and returnes the previous format in case you need to revert back in the future.
Types ¶
type Bool ¶
type Bool bool
Bool is a wrapper for the native bool type which provides an Eval function so that it satisfies the Exp interface.
type Exp ¶
The Exp interface represents a tree node. There are several implementations of the interface in this package, but one may define custom Exp's as long as they implement the Eval function.
func After ¶
After is an expression that evaluates to true if date is a time after the evaluated date. The value is parsed to a time.Time before comparing.
func Before ¶
Before evaluates to true if date is before the date pointed to by key. The value is parsed to a time.Time before comparing. In case of a parse error false is returned.
func Contains ¶
Contains is an expression that evaluates to true if substr is within the value pointed to by key.
func ContainsAny ¶
ContainsAny evaluates to true if any Unicode code points in chars are within the value pointed to by key.
func ContainsRune ¶
ContainsRune evaluates to true if the Unicode code point r is within the value pointed to by key.
func Count ¶
Count evaluates to true if the number of non-overlapping instances of sep in the value pointed to by key is equal to count.
func Day ¶
Day is an expression that evaluates to true if the date pointed to by key is on the specified day.
func Equal ¶
Equal evaluates to true if the value pointed to by key is equal in value to v. The value pointed to by k is parsed into a float64 before comparing. If a parse error occurs false is returned.
func EqualFold ¶
EqualFold evaluates to true if the value pointed to by key and s, interpreted as UTF-8 strings, are equal under Unicode case-folding.
func GreaterOrEqual ¶
GreaterOrEqual is a shorthand for Or(Gt(k, v), Eq(k, v)).
func GreaterThan ¶
GreaterThan evaluates to true if the value pointed to by key is greater in value than v. The value is parsed as float before performing the comparison.
func LessOrEqual ¶
LessOrEqual is a shorthand for Lt(Gt(k, v), Eq(k, v)).
func LessThan ¶
LessThan evaluates to true if the value pointed to by key is less in value than v. The value is parsed as float before performing the comparison.
func Match ¶
Match is an expression that evaluates to true if str is equal to the value pointed to by key.
func MatchAny ¶
MatchAny is an expression that evaluates to true if any of the strs are equal to the value pointed to by key.
func Month ¶
Month is an expression that evaluates to true if the date pointed to by key is on the specified month.
func On ¶
On evaluates to true if date is equal to the date pointed to by key. The value is parsed to a time.Time before comparing. In case of a parse error false is returned.
type Params ¶
Params defines the interface needed by Exp in order to be able to validate conditions. An example implementation of this interface would be https://golang.org/pkg/net/url/#Values.
Source Files