urbit/base/pub/doc/hoon/library/2ed.md
Anton Dyudin 6cbb6b060d Revert "remove docs for demo", "remove odds and ends", "demo network", "DEMO ONLY: root beak as %demo.", "DEMO ONLY: don't show doznec flapping.", "Prinrtf."
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	urb/zod/base/lib/drum.hoon
2015-06-15 18:10:02 -07:00

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section 2eD
===========
<h3 id="++bend"><code>++bend</code></h3>
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]
------------------------------------------------------------------------
<h3 id="++comp"><code>++comp</code></h3>
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
------------------------------------------------------------------------
<h3 id="++glue"><code>++glue</code></h3>
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]
------------------------------------------------------------------------
<h3 id="++less"><code>++less</code></h3>
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
------------------------------------------------------------------------
<h3 id="++pfix"><code>++pfix</code></h3>
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
------------------------------------------------------------------------
<h3 id="++plug"><code>++plug</code></h3>
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]
------------------------------------------------------------------------
<h3 id="++pose"><code>++pose</code></h3>
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
------------------------------------------------------------------------
<h3 id="++simu"><code>++simu</code></h3>
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
------------------------------------------------------------------------
<h3 id="++sfix"><code>++sfix</code></h3>
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
------------------------------------------------------------------------