4g: Parsing (Outside Caller) • Language • docs.urbit.org

`++rash`

Parse or crash

Parse a cord with a given rule and crash if the cord isn't entirely parsed.

Accepts

naf is an atom.

sab is a rule.

Produces

The value of the parse result, or crash.

Source

++  rash  |*([naf=@ sab=rule] (scan (trip naf) sab))

Examples

> (rash 'I was the world in which I walked, and what I saw' (star (shim 0 200)))
"I was the world in which I walked, and what I saw"

> (rash 'abc' (just 'a'))
! {1 2}
! 'syntax-error'
! exit

> (rash 'abc' (jest 'abc'))
'abc'

> (rash 'abc' (jest 'ab'))
! {1 3}
! 'syntax-error'
! exit

`++rose`

Parse to each

Parse tape los with rule sab, producing an (each @ud (unit *)). If los was not fully consumed, the result is %.n and p contains the column number before failure occurred. If los was fully consumed, the result is %.y and p contains either sab's result in a unit, or a null unit if parsing failed.

Accepts

los is a tape.

sab is a rule.

Produces

(each @ud (unit *)), where the * is whatever type the rule produces.

Source

++  rose  |*  [los=tape sab=rule]
          =+  vex=(sab [[1 1] los])
          =+  len=(lent los)
          ?.  =(+(len) q.p.vex)  [%| p=(dec q.p.vex)]
          ?~  q.vex
            [%& p=~]
          [%& p=[~ u=p.u.q.vex]]

Examples

> (rose "!" zap)
[%.y p=[~ u='!']]

> (rose "?" zap)
[%.n p=0]

> (rose "!?" zap)
[%.n p=1]

> (rose "!" ;~(plug zap fail))
[%.y p=~]

`++rush`

Parse or null

Parse an atom with a given rule and produce null if the cord isn't entirely parsed.

Accepts

naf is an atom.

sab is a rule.

Produces

The value of the parse result, or null.

Source

++  rush  |*([naf=@ sab=rule] (rust (trip naf) sab))

Examples

> (rush 'I was the world in which I walked, and what I saw' (star (shim 0 200)))
[~ "I was the world in which I walked, and what I saw"]

> (rush 'abc' (just 'a'))
~

> (rush 'abc' (jest 'abc'))
[~ 'abc']

> (rush 'abc' (jest 'ac'))
~

> (rush 'abc' (jest 'ab'))
~

`++rust`

Parse tape or null

Parse a tape with a given rule and produce null if the tape isn't entirely parsed.

Accepts

los is a tape.

sab is a rule.

Produces

A (unit *), where * is the type produced by sab.

Source

++  rust  |*  [los=tape sab=rule]
          =+  vex=((full sab) [[1 1] los])
          ?~(q.vex ~ [~ u=p.u.q.vex])

Examples

> (rust "I was the world in which I walked, and what I saw" (star (shim 0 200)))
[~ "I was the world in which I walked, and what I saw"]

> (rust "Or heard or felt came not but from myself;" (star (shim 0 200)))
[~ "Or heard or felt came not but from myself;"]

> (rust "And there I found myself more truly and more strange." (jest 'And there I'))
~

`++scan`

Parse tape or crash

Parse a tape with a given rule and crash if the tape isn't entirely parsed.

Accepts

los is a tape.

sab is a rule.

Produces

Either a tape or a crash.

Source

++  scan  |*  [los=tape sab=rule]
          =+  vex=((full sab) [[1 1] los])
          ?~  q.vex
            ~_  (show [%m '{%d %d}'] p.p.vex q.p.vex ~)
            ~_(leaf+"syntax error" !!)
          p.u.q.vex

Examples

> (scan "I was the world in which I walked, and what I saw" (star (shim 0 200)))
"I was the world in which I walked, and what I saw"

> (scan "Or heard or felt came not but from myself;" (star (shim 0 200)))
"Or heard or felt came not but from myself;"

> (scan "And there I found myself more truly and more strange." (jest 'And there I'))
! {1 12}
! 'syntax-error'
! exit