> For the complete documentation index, see [llms.txt](https://docs.urbit.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.urbit.org/hoon/stdlib/3g.md).
# 3g: Molds and Mold-Builders
Molds for syntax parsing including coin literals, dimes, and format specifiers.
## `$coin`
Noun-literal syntax cases.
Syntax cases for `$noun`s-literal: `$atom`s, jammed `$noun`s, and nestable tuples. Parsed and printed using `+so` and `+co` cores.
#### Source
```hoon
+$ coin $~ [%$ %ud 0]
$% [%$ p=dime]
[%blob p=*]
[%many p=(list coin)]
```
#### Examples
```
> `coin`(need (slay '~s1'))
[%$ p=[p=~.dr q=18.446.744.073.709.551.616]]
```
```
> `coin`(need (slay '0x2b59'))
[%$ p=[p=~.ux q=11.097]]
```
```
> ~(rend co [%many ~[[%$ %ud 1] [%$ %tas 'a'] [%$ %s -2]]])
"._1_a_-2__"
```
```
> ._1_a_-2__
[1 %a -2]
```
```
> `@uv`(jam [3 4])
0v2cd1
```
```
> (slay '~02cd1')
[~ u=[%blob p=[3 4]]]
```
```
> ~02cd1
[3 4]
```
***
## `$dime`
Aura-atom pair.
Used in `+coin`. Convenience methods [`+scot`](/hoon/stdlib/4m.md#scot) and [`+scow`](/hoon/stdlib/4m.md#scow) print dimes as `+cord` and `$tape`, respectively. [`+slat`](/hoon/stdlib/4m.md#slat), [`+slav`](/hoon/stdlib/4m.md#slav), and [`+slaw`](/hoon/stdlib/4m.md#slaw) are used to parse `$atom`s of specific auras.
#### Source
```hoon
+$ dime [p=@ta q=@]
```
#### Examples
```
> +>:(slay '0x123')
p=[p=~.ux q=291]
```
***
## `$edge`
Parsing location metadata. Parsing location input `.p` and optional result `p.q` and parsing continuation `q.q`.
#### Source
```hoon
+$ edge [p=hair q=(unit [p=* q=nail])]
```
#### Examples
```
> *edge
[p=[p=0 q=0] q=~]
```
```
> (tall:vast [1 1] "a b")
[p=[p=1 q=3] q=[~ u=[p=[%wing p=~[%a]] q=[p=[p=1 q=2] q=" b"]]]]
```
#### Discussion
See also: [`$rule`](#rule).
***
## `$hair`
Parsing line and column.
A pair of two `@ud` used in parsing indicating line and column number.
#### Source
```hoon
+$ hair [p=@ud q=@ud]
```
#### Examples
```
> *hair
[p=0 q=0]
```
```
> `hair`[1 1]
[p=1 q=1]
```
```
> ((plus ace) [1 1] " --")
[p=[p=1 q=4] q=[~ u=[p=[~~. " "] q=[p=[p=1 q=4] q="--"]]]]
```
```
> `hair`p:((plus ace) [1 1] " --")
[p=1 q=4]
```
***
## `+like`
Generic edge.
Generates an [`$edge`](#edge) with a parsed result set to a specific type.
#### Source
```hoon
++ like |* a=$-(* *)
|: b=`*`[(hair) ~]
:- p=(hair -.b)
^= q
?@ +.b ~
:- ~
u=[p=(a +>-.b) q=[p=(hair -.b) q=(tape +.b)]]
```
#### Examples
```
> *(like char)
[p=[p=0 q=0] q=~]
```
```
> (ace [1 1] " a")
[p=[p=1 q=2] q=[~ u=[p=' ' q=[p=[p=1 q=2] q="a"]]]]
```
```
> `(like char)`(ace [1 1] " a")
[p=[p=1 q=2] q=[~ [p=~~. q=[p=[p=1 q=2] q="a"]]]]
```
```
> `(like ,@)`(ace [1 1] " a")
[p=[p=1 q=2] q=[~ u=[p=32 q=[p=[p=1 q=2] q="a"]]]]
```
***
## `$nail`
Location, remainder of parsed text.
Indicates parsing position `.p`, and remaining text to be parsed `.q`.
#### Source
```hoon
+$ nail [p=hair q=tape]
```
#### Examples
```
> +<:;~(plug cab cab)
c=[p=[p=0 q=0] q=""]
```
***
## `$pint`
Parsing range.
A `$pint` is a pair of [`$hair`](#hair), indicating from `.p` to `.q`. Mostly used for stack traces.
#### Source
```hoon
+$ pint [p=[p=@ q=@] q=[p=@ q=@]]
```
#### Examples
```
> !:(!!)
/~zod/base/~2014.9.20..01.22.04..52e3/:<[1 4].[1 6]>
```
```
> `pint`[[1 4] [1 6]]
[p=[p=1 q=4] q=[p=1 q=6]]
```
***
## `$rule`
Parsing rule.
An empty parsing rule, but used to check that parsing rules match this with `_`.
#### Source
```hoon
+$ rule _|:($:nail $:edge)
```
#### Examples
```
> ([|=(a=nail [p.a ~ u=['a' a]])]:|6 [1 1] "hi")
[[p=1 q=1] ~ u=['a' p=[p=1 q=1] q="hi"]]
```
***
## `$spot`
Stack trace line.
The stack trace that is printed after crashing.
#### Source
```hoon
++ spot [p=path q=pint]
```
#### Examples
```
> !: !!
/~zod/base/~2018.8.8..21.42.40..7852:<[1 5].[1 7]>
! exit
```
***
## `$tone`
Nock result, error report.
Produces either success (`%0`), a block with list of requests blocked on (`%1`), or failure with an error report (`%2`).
#### Source
```hoon
+$ tone $% [%0 product=*]
[%1 block=*]
[%2 trace=(list [@ta *])]
==
```
#### Examples
```
> (mink [[20 21] 0 3] $~)
[%0 product=21]
```
```
> (mink [[1 2] !=(!:(+(.)))] ,~)
[%2 trace=~[[~.spot [[1.685.027.454 1.702.060.386 20.241.306.789.072.368.304.935.424.358.627.395.315.601.229.215.400.789.787.861.332.606 0] [1 20] 1 24]]]]
```
***
## `$toon`
Nock result, stack trace.
Produces either success (`%0`), a block with list of requests blocked on (`%1`), or failure with a stack trace (`%2`).
#### Source
```hoon
+$ toon $% [%0 p=*] :: success
[%1 p=*] :: block
[%2 p=(list tank)] :: stack trace
== ::
```
#### Examples
```
> (mock [[20 21] 0 3] $~)
[%0 p=21]
```
```
> (mock [[1 2] !=(!:(+(.)))] ,~)
[ %2
p
~[
[ %rose
p=[p=":" q="" r=""]
q=[i=[%rose p=[p="/" q="/" r=""] q=[i=[%leaf p="~zod"] t=[i=[%leaf p="base"] t=[i=[%leaf p="~2021.10.16..10.03.16..59ee"] t=~]]]] t=[i=[%leaf p="<[1 20].[1 24]>"] t=~]]
]
]
]
```
***
## `+wonk`
Product from edge.
Pull result out of a [`$edge`](#edge), or crash if there's no result.
#### Source
```hoon
++ wonk |* veq=_$:edge
?~(q.veq !! p.u.q.veq)
```
#### Examples
```
> (wide:vast [1 1] "(add 2 2)")
[p=[p=1 q=10] q=[~ [p=[%cncl p=[%wing p=~[%add]] q=~[[%sand p=%ud q=2] [%sand p=%ud q=2]]] q=[p=[p=1 q=10] q=""]]]]
```
```
> (wonk (wide:vast [1 1] "(add 2 2)"))
[%cncl p=[%wing p=~[%add]] q=~[[%sand p=%ud q=2] [%sand p=%ud q=2]]]
```
#### Discussion
See also: [`$edge`](#edge)
***
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