feat(parse): add discarding combinators, move discard

- add repeatD, oneOrMoreD, zeroOrMoreD
thi-ng · Apr 20, 2020 · e09a2c4 · e09a2c4
1 parent 822fcba
commit e09a2c4
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Showing 6 changed files with 27 additions and 7 deletions.
diff --git a/packages/parse/src/combinators/alt.ts b/packages/parse/src/combinators/alt.ts
@@ -1,5 +1,5 @@
 import type { Parser } from "../api";
-import { discard } from "./discard";
+import { discard } from "../xform/discard";
 
 export const alt = <T>(parsers: Parser<T>[]): Parser<T> => (ctx) => {
     if (ctx.done) return false;

diff --git a/packages/parse/src/combinators/discard.ts b/packages/parse/src/combinators/discard.ts
diff --git a/packages/parse/src/combinators/repeat.ts b/packages/parse/src/combinators/repeat.ts
@@ -1,4 +1,5 @@
 import type { Parser } from "../api";
+import { discard } from "../xform/discard";
 
 export const repeat = <T>(
     parser: Parser<T>,
@@ -32,3 +33,12 @@ export const oneOrMore = <T>(
     id = "repeat1",
     max = Infinity
 ) => repeat(parser, 1, max, id);
+
+export const repeatD = <T>(parser: Parser<T>, min: number, max: number) =>
+    discard(repeat(parser, min, max));
+
+export const zeroOrMoreD = <T>(parser: Parser<T>, max = Infinity) =>
+    repeatD(parser, 0, max);
+
+export const oneOrMoreD = <T>(parser: Parser<T>, max = Infinity) =>
+    repeatD(parser, 1, max);
diff --git a/packages/parse/src/combinators/seq.ts b/packages/parse/src/combinators/seq.ts
@@ -1,5 +1,5 @@
 import type { Parser } from "../api";
-import { discard } from "./discard";
+import { discard } from "../xform/discard";
 
 export const seq = <T>(parsers: Parser<T>[], id = "seq"): Parser<T> => (
     ctx

diff --git a/packages/parse/src/index.ts b/packages/parse/src/index.ts
@@ -6,7 +6,6 @@ export * from "./grammar";
 export * from "./combinators/alt";
 export * from "./combinators/boundary";
 export * from "./combinators/check";
-export * from "./combinators/discard";
 export * from "./combinators/dynamic";
 export * from "./combinators/expect";
 export * from "./combinators/maybe";
@@ -41,6 +40,7 @@ export * from "./readers/string-reader";
 
 export * from "./xform/collect";
 export * from "./xform/comp";
+export * from "./xform/discard";
 export * from "./xform/hoist";
 export * from "./xform/join";
 export * from "./xform/number";

diff --git a/packages/parse/src/xform/discard.ts b/packages/parse/src/xform/discard.ts
@@ -0,0 +1,14 @@
+import type { Parser } from "../api";
+import { xform } from "../combinators/xform";
+
+/**
+ * Discards AST node and any of its children.
+ */
+export const xfDiscard = () => null;
+
+/**
+ * Syntax sugar for `xform(parser, xfDiscard)`.
+ *
+ * @param parser
+ */
+export const discard = (parser: Parser<any>) => xform(parser, xfDiscard);