2a: Unit Logic

    ++biff

    Unit as argument

    Applies a function b that produces a unit to the unwrapped value of ++unit a (u.a). If a is empty, ~ is produced.

    Accepts

    a is a unit.

    b is a function that accepts a noun and produces a unit.

    Produces

    A unit.

    Source

        ++  biff
          |*  [a](unit) b]$-(* (unit))]
          ?~  a  ~
          (b u.a)
    

    Examples

        > (biff (some 5) |=(a]@ (some (add a 2))))
        [~ u=7]
    
        > (biff ~ |=(a]@ (some (add a 2))))
        ~
    

    ++bind

    Non-unit function to unit, producing unit

    Applies a function b to the value (u.a) of a ++unit a, producing a unit. Used when you want a function that does not accept or produce a unit to both accept and produce a unit.

    Accepts

    a is a unit.

    b is a function.

    Produces

    A unit.

    Source

        ++  bind
          |*  [a=(unit) b=gate]
          ?~  a  ~
          [~ u=(b u.a)]
    

    Examples

        > (bind ((unit @) [~ 97]) ,@t)
        [~ u='a']
    
        > =a |=(a]@ (add a 1))
        > (bind ((unit @) [~ 2]) a)
        [~ u=3]
    

    ++bond

    Replace null

    Replaces an empty ++unit b with the product of a called trap a. If the unit is not empty, then the original unit is produced.

    Accepts

    a is a trap.

    b is a unit.

    Produces

    Either the product of a or the value inside of unit b.

    Source

        ++  bond
          |*  a=(trap)
          |*  b=(unit)
          ?~  b  $:a
          u.b
    

    Examples

        > (bex 10)
        1.024
        > ((bond |.((bex 10))) ~)
        1.024
    
        > ((bond |.((bex 10))) (slaw %ud '123'))
        123
    

    ++both

    Group unit values into pair

    Produces ~ if either a or b are empty. Otherwise, produces a ++unit whose value is a cell of the values of two input units a and b.

    Accepts

    a is a unit.

    b is a unit.

    Produces

    A unit of the two initial values.

    Source

        ++  both
          |*  [a=(unit) b=(unit)]
          ?~  a  ~
          ?~  b  ~
          [~ u=[u.a u.b]]
    

    Examples

        > (both (some 1) (some %b))
        [~ u=[1 %b]]
    
        > (both ~ (some %b))
        ~
    

    ++clap

    Apply function to two units

    Applies a binary function c--which does not usually accept or produce a ++unit-- to the values of two units, a and b, producing a unit.

    Accepts

    a is a unit.

    b is a unit.

    c is a function that performs a binary operation.

    Produces

    A unit.

    Source

        ++  clap                                                ::  combine
          |*  [a](unit) b=(unit) c=_|=(^ +<-)]
          ?~  a  b
          ?~  b  a
          [~ u=(c u.a u.b)]
    

    Examples

        > =u ((unit @t) [~ 'a'])
        > =v ((unit @t) [~ 'b'])
        > (clap u v |=([a=@t b=@t] (welp (trip a) (trip b))))
        [~ u="ab"]
    
        > =a ((unit @u) [~ 1])
        > =b ((unit @u) [~ 2])
        > =c |=([a=@ b=@] (add a b))
    
        > (clap a b c)
        [~ 3]
    

    ++drop

    Unit to list

    Makes a ++list of the unwrapped value (u.a) of a ++unit a.

    Accepts

    a is a unit.

    Produces

    A list.

    Source

        ++  drop                                                ::  enlist
          |*  a=(unit)
          ?~  a  ~
          [i=u.a t=~]
    

    Examples

        > =a ((unit @) [~ 97])
        > (drop a)
        [i=97 t=~]
    
        > =a ((unit @) [~])
        > (drop a)
        ~
    

    ++fall

    Give unit a default value

    Produces a default value b for a ++unit a in cases where a is null.

    Accepts

    a is a unit.

    b is a noun that's used as the default value.

    Produces

    Either a noun b or the unwrapped value of unit a.

    Source

        ++  fall                                                ::  default
          |*  [a=(unit) b=*]
          ?~(a b u.a)
    

    Examples

        > (fall ~ `a`)
        `a`
        > (fall [~ u=0] `a`)
        0
    

    ++lift

    Curried bind

    Accepts a ++gate a and produces a function that accepts ++unit b to which it applies a. Used when you want a function that does not accept or produce a unit to both accept and produce a unit.

    Accepts

    a is a gate.

    b is a unit.

    Produces

    A unit.

    Source

        ++  lift                                                ::  lift gate (fmap)
          |*  a=gate                                            ::  flipped
          |*  b=(unit)                                          ::  curried
          (bind b a)                                            ::  bind
    

    Examples

        > ((lift dec) `(unit @)`~)
        ~
    
        > ((lift dec) `(unit @)`[~ 20])
        [~ 19]
    

    ++mate

    Choose

    Accepts two units a and b whose values are expected to be equivalent. If either is empty, then the value of the other is produced. If neither are empty, it asserts that both values are the same and produces that value. If the assertion fails, ++mate crashes with 'mate' in the stack trace.

    Accepts

    a is a unit.

    b is a unit.

    Produces

    A unit or crash.

    Source

        ++  mate                                                ::  choose
          |*  [a=(unit) b=(unit)]
          ?~  b  a
          ?~  a  b
          ?.(=(u.a u.b) ~|('mate' !!) a)
    

    Examples

        > =a ((unit @) [~ 97])
        > =b ((unit @) [~ 97])
        > (mate a b)
        [~ 97]
    
        > =a ((unit @) [~ 97])
        > =b ((unit @) [~])
        > (mate a b)
        [~ 97]
    
        > =a ((unit @) [~ 97])
        > =b ((unit @) [~ 98])
        > (mate a b)
        ! 'mate'
        ! exit
    

    ++need

    Unwrap unit

    Retrieve the value from a ++unit and crash if the unit is null.

    Accepts

    a is a unit.

    Produces

    Either the unwrapped value of a (u.a), or crash.

    Source

        ++  need                                                ::  demand
          |*  a](unit)
          ?~  a  ~|(%need !!)
          u.a
    

    Examples

        > =a ((unit [@t @t]) [~ ['a' 'b']])
        > (need a)
        ['a' 'b']
    
        > =a ((unit @ud) [~ 17])
        > (need a)
        17
    
        > =a ((unit @) [~])
        > (need a)
        ! exit
    

    ++some

    Wrap value in a unit

    Takes any atom a and produces a ++unit with the value set to a.

    Accepts

    a is a noun.

    Produces

    A unit.

    Source

        ++  some                                                ::  lift (pure)
          |*  a=*
          [~ u=a]
    

    Examples

        > (some [`a` `b`])
        [~ u=[`a` `b`]]
    
        > (some &)
        [~ u=%.y]