Documentation
¶
Overview ¶
Package formula implements very simple but fast formula parsing and evaluating. It uses the AST package to parse expressions in the formula which it transforms to executable functions.
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type ErrInsufficientArgs ¶
type ErrInsufficientArgs struct {
// Func is the name of the function.
Func string
// Pos is the character position of Func.
Pos int
// Actual is the number of arguments provided to Func.
Actual int
// Expected is the minimum number of arguments expected by Func.
Expected int
}
ErrInsufficientArgs is returned when a function in a formula requires more arguments than that provided.
func (*ErrInsufficientArgs) Error ¶
func (e *ErrInsufficientArgs) Error() string
Error implements error.
type ErrPanic ¶
type ErrPanic struct {
// Func is the name of the function.
Func string
// Pos is the character position of Func.
Pos int
// Reason for panic.
Reason string
// Filename of where panic occurred.
File string
// Line number of where panic occurred.
Line int
}
ErrPanic is returned when a registered function panics.
type ErrUnknownFunc ¶
type ErrUnknownFunc struct {
// Func is the name of the unknown function encountered.
Func string
// Pos is the character position of the unknown Func.
Pos int
}
ErrUnknownFunc is returned when a formula contains an unrecognized function.
type ErrUnknownVariable ¶
type ErrUnknownVariable struct {
// Var is the name of the unknown variable or constant.
Var string
// Pos is the character position of the unknown variable or constant.
Pos int
}
ErrUnknownVariable is returned when a formula contains an unrecognized variable or constant.
func (*ErrUnknownVariable) Error ¶
func (e *ErrUnknownVariable) Error() string
Error implements error.
type Formula ¶
type Formula struct {
// contains filtered or unexported fields
}
Formula is a parsed formula that is ready to be evaluated. It is safe to use concurrently from multiple goroutines.
func New ¶
New returns a new formula for a given string. The formula is parsed and may be evaluated if parsed successfully. If not successful, an error is returned and the formula is nil.
Most functions from the math package that return a single float64 are supported. The equivalent function name is all lower-cased. Therefore RoundToEven becomes roundtoeven. See https://golang.org/pkg/math/.
func (*Formula) Eval ¶
Eval evaluates a formula using the variables passed. If an unknown variable/constant or function is encountered, ErrUnknownVariable or ErrUnknownFunc is returned respectively. If a known function is passed with too few arguments, ErrInsufficientArgs is returned.
Some special math constants are already included. They are automatically defined unless over-ridden by variables. These are: π, 𝜋, pi, Φ, phi, e, E.
func (*Formula) RegisterFunc ¶
RegisterFunc registers a custom function to be usable by the formula. This function allows an arbitrary number of input floats and one output float. The paramCount passed indicates the number of input floats expected. If less than the required paramCount arguments are passed to the function, Eval will return an ErrInsufficientArgs error. The function does not need to internally check the correct arg length. Functions must be registered with the formula before evaluating.
Example:
// Add sinc function: https://en.wikipedia.org/wiki/Sinc_function
RegisterFunc("sinc", 1, func(args ...float64) float64 {
if args[0] == 0 {
return 1
}
return math.Sin(args[0]) / args[0]
})
type Variable ¶
type Variable struct {
// contains filtered or unexported fields
}
Variable represents a variable with a specific name and value, that may be passed to a formula.
Source Files