ac1a31c · urbit.org · git.iko.soy

git.iko.soy/urbit.org

Fixed example in parsing.md

example used `lit` and `rit` where `pal` and `par` are proper now. example previously had a syntax error on line 2: `|^ (scan xprs tape)` corrected to `|^ (scan xprs expr)`

commitac1a31cce3a0c866e4a7938887df6fd9c17fd193 authorrisruc-habteb <58319961+risruc-habteb@users.noreply.github.com> dateTue 19 Jan 2021, 12:22 (6 years ago) parent499160b

1 file changed+8−8

compare with master

unifiedsplit

tutorials/hoon/parsing.md+8−8

tutorials/hoon/parsing.md+8−8

@@ -321,10 +321,10 @@ documented among the [parser builders](@/docs/reference/library/4f.md).

321321surrounded on both sides by text that matches a pair of `rule`s, which is discarded.

322322

323323```

324−> (scan "(42)" (ifix [lit rit] (jest '42')))

324+> (scan "(42)" (ifix [pal par] (jest '42')))

325325'42'

326326```

327−`+lit` and `+rit` are shorthand for `(just '(')` and `(just ')')`, respectively. All

327+`+pal` and `+par` are shorthand for `(just '(')` and `(just ')')`, respectively. All

328328ASCII glyphs have counterparts of this sort, documented

329329[here](@/docs/reference/library/4h.md).

330330

@@ -520,13 +520,13 @@ your `gen/` folder.

520520:: expr-parse: parse arithmetic expressions

521521::

522522|= xprs=tape

523−|^ (scan xprs tape)

523+|^ (scan xprs expr)

524524++ factor

525525 %+ knee *@ud

526526 |. ~+

527527 ;~ pose

528528 dem

529− (ifix [lit rit] expr)

529+ (ifix [pal par] expr)

530530 ==

531531++ turm

532532 %+ knee *@ud

@@ -563,15 +563,15 @@ for expressions.

563563 |. ~+

564564 ;~ pose

565565 dem

566− (ifix [lit rit] expr)

566+ (ifix [pal par] expr)

567567 ==

568568```

569569

570570A _factor_ is either a decimal number or an expression surrounded by parentheses. Put

571571into Hoon terms, a decimal number is parsed by the `rule` `+dem` and an

572572expression is parsed by removing the surrounding parentheses and then passing

573−the result to the expression parser arm `+expr`, given by the `rule` `(ifix [lit

574−rit] expr)`. Since we want to parse our expression with one or the other, we

573+the result to the expression parser arm `+expr`, given by the `rule` `(ifix [pal

574+par] expr)`. Since we want to parse our expression with one or the other, we

575575chain these two `rule`s together using the monadic applicator rune `;~` along

576576with `+pose`, which says to try each rule in succession until one of them works.

577577

@@ -584,7 +584,7 @@ Then follows the definition of the gate utilized by `+knee`:

584584 |. ~+

585585 ;~ pose

586586 dem

587− (ifix [lit rit] expr)

587+ (ifix [pal par] expr)

588588 ==

589589```

590590`~+` is used to cache the parser, so that it does not need to be computed over