urbit/pub/docs/dev/hoon/library/2ed.md
Galen Wolfe-Pauly bb495844be doc -> docs
2015-10-20 10:51:45 -07:00

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section 2eD

++bend

Conditional composer

++  bend                                                ::  conditional comp
  ~/  %bend
  |*  raq=_|*([a=* b=*] [~ u=[a b]])
  ~/  %fun
  |*  [vex=edge sab=_rule]
  ?~  q.vex
    vex
  =+  yit=(sab q.u.q.vex)
  =+  yur=(last p.vex p.yit)
  ?~  q.yit
    [p=yur q=q.vex]
  =+  vux=(raq p.u.q.vex p.u.q.yit)
  ?~  vux
    [p=yur q=q.vex]
  [p=yur q=[~ u=[p=u.vux q=q.u.q.yit]]]
::

Parsing composer: connects the edge vex with the subsequent rule sab as an optional suffix, using the gate raq to compose or reject its result. If there is no suffix, or if the suffix fails to be composed with the current result, the current result is produced. Used to map a group of rules to a specified output.

raq is a gate.

sab is a rule.

vex is an edge.

~zod/try=> (;~((bend |=([a=char b=char] ?.(=(a b) ~ (some +(a))))) prn prn) [1 1] "qs")
[p=[p=1 q=3] q=[~ u=[p=~~q q=[p=[p=1 q=2] q="s"]]]]
~zod/try=> (;~((bend |=([a=char b=char] ?.(=(a b) ~ (some +(a))))) prn prn) [1 1] "qqq")
[p=[p=1 q=3] q=[~ u=[p=~~r q=[p=[p=1 q=3] q="q"]]]]
~zod/try=> (scan "aa" ;~((bend |=([a=char b=char] ?.(=(a b) ~ (some +(a))))) prn prn))
~~b
~zod/try=> (scan "ba" ;~((bend |=([a=char b=char] ?.(=(a b) ~ (some +(a))))) prn prn))
! {1 3}
! exit
~zod/try=> `(unit ,@tas)`(scan "" ;~((bend) (easy ~) sym))
~
~zod/try=> `(unit ,@tas)`(scan "sep" ;~((bend) (easy ~) sym))
[~ %sep]

++comp

Arbitrary compose

++  comp
  ~/  %comp
  |*  raq=_|*([a=* b=*] [a b])                          ::  arbitrary compose
  ~/  %fun
  |*  [vex=edge sab=_rule]
  ?~  q.vex
    vex
  =+  yit=(sab q.u.q.vex)
  =+  yur=(last p.vex p.yit)
  ?~  q.yit
    [p=yur q=q.yit]
  [p=yur q=[~ u=[p=(raq p.u.q.vex p.u.q.yit) q=q.u.q.yit]]]
::

Parsing composer: connects the edge vex with a following rule sab, combining the contents of vex with the result of sab using a binary gate raq. Used to fold over the results of several rules.

raq is a gate that accepts a cell of two nouns, a and b, and produces a cell of two nouns.

sab is a rule.

vex is an edge.

~zod/try=> (scan "123" ;~((comp |=([a=@u b=@u] (add a b))) dit dit dit))
6
~zod/try=> (scan "12" ;~((comp |=([a=@u b=@u] (add a b))) dit dit dit))
! {1 3}
! exit

++glue

Skip delimiter

++  glue                                                ::  add rule
  ~/  %glue
  |*  bus=_rule
  ~/  %fun
  |*  [vex=edge sab=_rule]
  (plug vex ;~(pfix bus sab))
::

Parsing composer: connects an edge vex with a following rule sab by parsing the rule bus (the delimiting symbol) and throwing out the result.

bus is a rule.

sab is a rule.

vex is an edge.

~zod/try=> (scan "200|mal|bon" ;~((glue bar) dem sym sym))
[q=200 7.102.829 7.237.474]
~zod/try=> `[@u @tas @tas]`(scan "200|mal|bon" ;~((glue bar) dem sym sym))
[200 %mal %bon]
~zod/try=>  (scan "200|;|bon" ;~((glue bar) dem sem sym))
[q=200 ~~~3b. 7.237.474]
~zod/try=>  (scan "200.;.bon" ;~((glue dot) dem sem sym))
[q=200 ~~~3b. 7.237.474]

++less

Parse unless

++  less                                                ::  no first and second
  |*  [vex=edge sab=_rule]
  ?~  q.vex
    =+  roq=(sab)
    [p=(last p.vex p.roq) q=q.roq]
  vex(q ~)
::

Parsing composer: if an edge vex reflects a success, fail. Otherwise, connect vex with the following rule.

sab is a rule.

vex is an edge.

~zod/try=> (scan "sas-/lo" (star ;~(less lus bar prn)))
"sas-/lo"
~zod/try=> (scan "sas-/l+o" (star ;~(less lus bar prn)))
! {1 8}
! exit
~zod/try=> (scan "sas|-/lo" (star ;~(less lus bar prn)))
! {1 5}
! exit

++pfix

Discard first rule

++  pfix                                                ::  discard first rule
  ~/  %pfix
  (comp |*([a=* b=*] b))
::

Parsing composer: connects an edge vex with two subsequent rules, ignoring the result of the first and producing the result of the second.

vex is an edge.

~zod/try=> `@t`(scan "%him" ;~(pfix cen sym))
'him'
~zod/try=> (scan "+++10" ;~(pfix (star lus) dem))
q=10

++plug

Parse to tuple

++  plug                                                ::  first then second
  ~/  %plug
  |*  [vex=edge sab=_rule]
  ?~  q.vex
    vex
  =+  yit=(sab q.u.q.vex)
  =+  yur=(last p.vex p.yit)
  ?~  q.yit
    [p=yur q=q.yit]
  [p=yur q=[~ u=[p=[p.u.q.vex p.u.q.yit] q=q.u.q.yit]]]
::

Parsing composer: connects vex with a following rule sab, producing a cell of both the results. See also: the monad applicator ;~ for a more detailed explanation.

sab is a rule.

vex is an edge.

~zod/try=> (scan "1..20" ;~(plug dem dot dot dem))
[q=1 ~~~. ~~~. q=20]
~zod/try=> (scan "moke/~2014.1.1" ;~(plug sym fas nuck:so))
[1.701.539.693 ~~~2f. [% p=[p=~.da q=170.141.184.500.766.106.671.844.917.172.921.958.400]]]
~zod/try=> ;;(,[@tas @t ~ %da @da] (scan "moke/~2014.1.1" ;~(plug sym fas nuck:so)))
[%moke '/' ~ %da ~2014.1.1]

++pose

Parse options

++  pose                                                ::  first or second
  ~/  %pose
  |*  [vex=edge sab=_rule]
  ?~  q.vex
    =+  roq=(sab)
    [p=(last p.vex p.roq) q=q.roq]
  vex

Parsing composer: if vex reflects a failure, connect it with the following rule sab. See also: the monad applicator ;~

sab is a rule.

vex is an edge.

~zod/try=> `@t`(scan "+" ;~(pose lus tar cen))
'+'
~zod/try=> `@t`(scan "*" ;~(pose lus tar cen))
'*'
~zod/try=> `@t`(scan "%" ;~(pose lus tar cen))
'%'
~zod/try=> `@t`(scan "-" ;~(pose lus tar cen))
! {1 1}
! exit

++simu

First and second

++  simu                                                ::  first and second
  |*  [vex=edge sab=_rule]
  ?~  q.vex
    vex
  =+  roq=(sab)
  roq
::

Parsing composer: if an edge vex reflects a failure, fail. Otherwise, connect vex with the following rule.

sab is a rule.

vex is an edge.

~zod/try=> (scan "~zod" scat:vast)
[%dtzy p=%p q=0]
~zod/try=> (scan "%zod" scat:vast)
[%dtzz p=%tas q=6.582.138]
~zod/try=> (scan "%zod" ;~(simu cen scat:vast))
[%dtzz p=%tas q=6.582.138]
~zod/try=> (scan "~zod" ;~(simu cen scat:vast))
! {1 1}
! exit

++sfix

Discard second rule

++  sfix                                                ::  discard second rule
  ~/  %sfix
  (comp |*([a=* b=*] a))

Parsing composer: connects vex with two subsequent rules returning the result of the first and discarding the result of the second.

a is the result of parsing the first rule.

b is the result of of parsing the second rule.

~zod/try=> `@t`(scan "him%" ;~(sfix sym cen))
'him'
~zod/try=> (scan "10+++" ;~(sfix dem (star lus)))
q=10