tribool - a little golang library

Package tribool implements a tri-state boolean where the extra state is indeterminate.

Getting started

To get the package, execute:

go get gopkg.in/grignaak/tribool.v1

To import this package, add the following line to your code:

import "gopkg.in/grignaak/tribool.v1"

Refer to it as tribool.

For more details, see the API documentation

Maybe

A tri-state boolean has the values False, True, and Maybe. Maybe represents a value that is either true or false but it is inderminate which it is. For example, you don't know if an http POST was successful if the connection is dropped after the request was made but before the response came back. This can be modeled with the indeterminate Maybe value.

Tribool provides tri-state logical operators that act like their boolean counterparts. The logic tables are documented below.

Parsing

The tribool package is especially useful for parsing flags that may need a default value. For example:

var x string // from somehere
var flag bool = tribool.FromString(x).WithMaybeAsFalse()

Parsing is case insensitive. The following table shows what will be parsed to true and false values, anything else (including the empty string) results in the indeterminate value.

case insensitive | result
-----------------+-------
               t | Yes
               y | Yes
               1 | Yes
              on | Yes
             yes | Yes
            true | Yes
               f | No
               n | No
               0 | No
              no | No
             off | No
           false | No
 <anything else> | Maybe

Truth Tables

Tribool supports the following binary operations:

	    |  and      or       nand        nor      xor    iff   implies 
	    | a ∧ b   a ∨ b   ¬(a ∧ b)   ¬(a ∨ b)   a ⊕ b  a ⇔ b  a ⇒ b    
	a b | b ∧ a   b ∨ a   ¬(b ∧ a)   ¬(b ∨ a)   b ⊕ a  b ⇔ a    —      
	----+-----------------------------------------------------------------
	N N |   N       N          Y          Y        N       Y      Y    
	N ? |   N       ?          Y          ?        ?       ?      Y    
	N Y |   N       Y          Y          N        Y       N      Y    
	? N |   N       ?          Y          ?        ?       ?      ?    
	? ? |   ?       ?          ?          ?        ?       ?      ?    
	? Y |   ?       Y          ?          N        ?       ?      Y    
	Y N |   N       Y          Y          N        Y       N      N    
	Y ? |   ?       Y          ?          N        ?       ?      ?    
	Y Y |   Y       Y          N          N        N       Y      Y    

Tribool supports the following unary operations:

	a | not   upgrade    downgrade
	--+----------------------------
	N |  Y       N          N
	? |  ?       Y          N
	Y |  N       Y          Y