README
¶
Package cloudeng.io/cmdutil/boolexpr
import cloudeng.io/cmdutil/boolexpr
Package boolexpr provides a boolean expression evaluator and parser. The supported operators are &&, || and ! (negation), and grouping via (). The set of operands is defined by clients of the package by implementing the Operand interface. Operands represent simple predicates against which the value supplied to the expression is evaluated, as such, they implicitly contain a value of their own that is assigned when the operand is instantiated. For example, a simple string comparison operand would be represented as "name='foo' || name='bar'" which evaluated to true if the expression is evaluated for "foo" or "bar", but not otherwise.
Types
Type Item
type Item struct {
// contains filtered or unexported fields
}
Item represents an operator or operand in an expression. It is exposed to allow clients packages to create their own parsers.
Functions
func AND() Item
And returns an AND item.
func LeftBracket() Item
LeftBracket returns a left bracket item.
func NOT() Item
NOT returns a NOT item.
func NewOperandItem(op Operand) Item
NewOperandItem returns an item representing an operand.
func OR() Item
OR returns an OR item.
func RightBracket() Item
RightBracket returns a right bracket item.
Methods
func (it Item) String() string
Type Operand
type Operand interface {
// Prepare is used to prepare the operand for evaluation, for example, to
// compile a regular expression. Document and String must be callable before
// Prepare is called. Eval and Needs must only be called after Prepare.
Prepare() (Operand, error)
// Eval must return false for any type that it does not support.
Eval(any) bool
// Needs returns true if the operand needs the specified type.
Needs(reflect.Type) bool
// Document returns a string documenting the operand.
Document() string
// String returns a string representation of the operand and its current value.
String() string
}
Operand represents an operand. It is exposed to allow clients packages to define custom operands.
Type Parser
type Parser struct {
// contains filtered or unexported fields
}
Functions
func NewParser() *Parser
Methods
func (p *Parser) ListOperands() []Operand
ListOperands returns the list of registered operands in alphanumeric order.
func (p *Parser) Parse(input string) (T, error)
Parse parses the supplied input into a boolexpr.T. The supported syntax is a boolean expression with and (&&), or (||) and grouping, via (). Operands are represented as = where the value is interpreted by the operand. The may be quoted using single-quotes or contain escaped runes via . The set of available operands is those registered with the parser before Parse is called.
func (p *Parser) RegisterOperand(name string, factory func(name, value string) Operand)
func (p *Parser) RemoveOperand(name string)
Type T
type T struct {
// contains filtered or unexported fields
}
T represents a boolean expression of regular expressions, file type and mod time comparisons. It is evaluated against a single input value.
Functions
func New(items ...Item) (T, error)
New returns a new matcher.T built from the supplied items.
Methods
func (m T) Eval(v any) bool
Eval evaluates the matcher against the supplied value. An empty, default matcher will always return false.
func (m T) Needs(typ any) bool
HasOperand returns true if the matcher's expression contains an instance of the specified operand.
func (m T) String() string
Documentation
¶
Overview ¶
Package boolexpr provides a boolean expression evaluator and parser. The supported operators are &&, || and ! (negation), and grouping via (). The set of operands is defined by clients of the package by implementing the Operand interface. Operands represent simple predicates against which the value supplied to the expression is evaluated, as such, they implicitly contain a value of their own that is assigned when the operand is instantiated. For example, a simple string comparison operand would be represented as "name='foo' || name='bar'" which evaluated to true if the expression is evaluated for "foo" or "bar", but not otherwise.
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Item ¶
type Item struct {
// contains filtered or unexported fields
}
Item represents an operator or operand in an expression. It is exposed to allow clients packages to create their own parsers.
func NewOperandItem ¶
NewOperandItem returns an item representing an operand.
type Operand ¶
type Operand interface {
// Prepare is used to prepare the operand for evaluation, for example, to
// compile a regular expression. Document and String must be callable before
// Prepare is called. Eval and Needs must only be called after Prepare.
Prepare() (Operand, error)
// Eval must return false for any type that it does not support.
Eval(any) bool
// Needs returns true if the operand needs the specified type.
Needs(reflect.Type) bool
// Document returns a string documenting the operand.
Document() string
// String returns a string representation of the operand and its current value.
String() string
}
Operand represents an operand. It is exposed to allow clients packages to define custom operands.
type Parser ¶
type Parser struct {
// contains filtered or unexported fields
}
func (*Parser) ListOperands ¶
ListOperands returns the list of registered operands in alphanumeric order.
func (*Parser) Parse ¶
Parse parses the supplied input into a boolexpr.T. The supported syntax is a boolean expression with and (&&), or (||) and grouping, via (). Operands are represented as <operand>=<value> where the value is interpreted by the operand. The <value> may be quoted using single-quotes or contain escaped runes via \. The set of available operands is those registered with the parser before Parse is called.
func (*Parser) RegisterOperand ¶
func (*Parser) RemoveOperand ¶
type T ¶
type T struct {
// contains filtered or unexported fields
}
T represents a boolean expression of regular expressions, file type and mod time comparisons. It is evaluated against a single input value.
func (T) Eval ¶
Eval evaluates the matcher against the supplied value. An empty, default matcher will always return false.
Source Files