23e92af · urbit.org · git.iko.soy

git.iko.soy/urbit.org

Merge pull request #932 from urbit/parsing-edits

parsing docs followup

commit23e92af9f588af24b7c4adfc328620250f7eeb57 authorDavid Kerschner <david@tlon.io> dateMon 17 Aug 2020, 13:01 (6 years ago) parentf1c6f98 ccd0c2a

2 files changed+8−4

compare with master

unifiedsplit

tutorials/arvo/cli-tutorial.md+1−2 tutorials/arvo/parsing.md+7−2

tutorials/arvo/cli-tutorial.md+1−2

@@ -336,8 +336,7 @@ Here begins the implementation of the additional arms required by the

336336`+command-parser` is of central importance - it is what is used to parse user

337337input and transform it into `command`s for the app to execute. Writing a proper

338338command parser requires understanding of the Hoon parsing functions found in the

339−standard library. How to do so may be found in the parsing documentation (coming

340−soon). For now, it is sufficient to know that this arm matches the text "demo" and

339+standard library. How to do so may be found in the [parsing tutorial](@/docs/tutorials/arvo/parsing.md). For now, it is sufficient to know that this arm matches the text "demo" and

341340produces a `[? command]`-shaped noun in response. Note how the `&` signifies that the command will be run as soon as it has been entered, without waiting for the user to press return.

342341

343342

tutorials/arvo/parsing.md+7−2

@@ -397,7 +397,7 @@ Understanding the rune `;~` is essential to building parsers with Hoon. Let's

397397take this opportunity to think about it carefully.

398398

399399The `rule` created by `;~(combinator [list rule])` may be understood

400−inductively. To this, let's consider the base case where our `[list rule]` has only a

400+inductively. To do this, let's consider the base case where our `[list rule]` has only a

401401single entry.

402402```

403403> (scan "star" ;~(plug (jest 'star')))

@@ -428,7 +428,7 @@ the gluing operation. And so, swapping `+plug` for `+pose` results in a crash,

428428which clues us into the fact that the combinator now has an effect since there

429429is more than one `rule`.

430430```

431−`> (scan "star" ;~(pose (jest 'st') (jest 'ar')))

431+> (scan "star" ;~(pose (jest 'st') (jest 'ar')))

432432{1 3}

433433syntax error

434434```

@@ -536,6 +536,11 @@ your `gen/` folder.

536536--

537537```

538538

539+Informally, the grammar here is:

540+ - A factor is either an integer or an expression surrounded by parentheses.

541+ - A term is either a factor or a factor times a term.

542+ - An expression is either a term or a term plus an expression.

543+

539544### Factors, terms, and expressions

540545

541546Our grammar consists of three `rule`s: one for factors, one for terms, and one