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7f673c4poprox6 years ago

tutorials/arvo/parsing.md+13−9

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unifiedsplit

@@ -236,7 +236,7 @@ and returns a `rule`.

236### `+cold`

237

238`+cold` is a `rule` builder that takes in a constant noun we'll call `cus` and a

239−`rule` we'll call `sef` and returns a `rule` identical to the `sef` except it

239+`rule` we'll call `sef`. It returns a `rule` identical to the `sef` except it

240replaces the parsing result with `cus`.

241

242Here we see that `p.q` of the `edge` returned by the `rule` created with `+cold`

@@ -267,8 +267,8 @@ utilizes parsers. That is to say, you'd like the programmer to only worry about

267passing `tape`s to the parser, and not have to dress up the `tape` as a `nail`

268themselves. Thus we have several functions for exactly this purpose.

269

270−These functions take in either a `tape` or an `@` (typically representing a

270+These functions take in either a `tape` or a `cord`,

271−`cord`) with a `rule` and attempts to parse the input with the `rule`. If the

271+alongside a `rule`, and attempt to parse the input with the `rule`. If the

272parse succeeds, it returns the result. There are crashing and unitized versions

273of each caller, corresponding to what happens when a parse fails.

274

@@ -486,8 +486,11 @@ to write the above `rule` is as follows:

486++ pars

487 |-

488 ;~ plug prn

489+ ;~ pose

489− ;~ pose knee *tape

490+ (knee *tape |.(^$))

490− |. ^$ (easy ~)

491+ (easy ~)

492+ ==

493+ ==

491```

494```

492

495

493You may want to utilize the `~+` rune when writing recursive parsers to cache

496You may want to utilize the `~+` rune when writing recursive parsers to cache

@@ -516,12 +519,12 @@ First lets look at the code we're going to use, and then dive into explaining

516it. If you'd like to follow along, save the following as `expr-parse.hoon` in

519it. If you'd like to follow along, save the following as `expr-parse.hoon` in

517your `gen/` folder.

520your `gen/` folder.

518```hoon

521```hoon

519−:: expr-parse: parse arithmetic expressions

522+:: expr-parse: parse arithmetic expressions

520::

523::

521|= xprs=tape

524|= xprs=tape

522|^ (scan xprs tape)

525|^ (scan xprs tape)

523++ factor

526++ factor

524− %+ knee @ud

527+ %+ knee *@ud

525 |. ~+

528 |. ~+

526 ;~ pose

529 ;~ pose

527 dem

530 dem

@@ -554,7 +557,8 @@ for expressions.

554```hoon

557```hoon

555++ factor

558++ factor

556 %+ knee @ud

559 %+ knee @ud

560+ |. ~+

557− |. ~+ ;~ pose

561+ ;~ pose

558 dem

562 dem

559 (ifix [lit rit] expr)

563 (ifix [lit rit] expr)

560 ==

564 ==

@@ -570,7 +574,7 @@ with `+pose`, which says to try each rule in succession until one of them works.

570

574

571Since expressions ultimately reduce to factors, we are actually building a

575Since expressions ultimately reduce to factors, we are actually building a

572recursive rule. Thus we need to make use of `+knee`. The first argument for

576recursive rule. Thus we need to make use of `+knee`. The first argument for

573−`+knee` is `@ud`, since our final answer should be a `@ud`.

577+`+knee` is `*@ud`, since our final answer should be a `@ud`.

574

578

575Then follows the definition of the gate utilized by `+knee`:

579Then follows the definition of the gate utilized by `+knee`:

576```hoon

580```hoon