Implement the variable sub-list operator v1 PROPOSED

Max Schillinger: 1
 Implement the variable sub-list operator

 4 files changed, 94 insertions(+), 4 deletions(-)

[PATCH] Implement the variable sub-list operator Export this patch

---
 ast/value.ha    | 14 ++++++++++++++
 interp/value.ha | 31 ++++++++++++++++++++++++++++++-
 parse/value.ha  | 29 +++++++++++++++++++++++++++--
 test/access.rc  | 24 +++++++++++++++++++++++-
 4 files changed, 94 insertions(+), 4 deletions(-)

diff --git a/ast/value.ha b/ast/value.ha
index 4f4ddc2..4c2f89f 100644
--- a/ast/value.ha
+++ b/ast/value.ha
@@ -24,6 +24,7 @@ export type access = struct {
 	atype: access_type,
 	target: str,
 	index: nullable *value,
+	end: nullable *value,
 };
 
 // A subscript value, e.g. `{echo hi}.
@@ -46,6 +47,13 @@ export fn value_finish(val: *value) void = {
 			value_finish(val);
 			free(val);
 		};
+		match (val.end) {
+		case null =>
+			yield;
+		case let val: *value =>
+			value_finish(val);
+			free(val);
+		};
 	case let val: string =>
 		free(val);
 	case let val: argument =>
@@ -81,6 +89,12 @@ export fn value_dup(val: *value) value = {
 			case let v: *value =>
 				yield alloc(value_dup(v));
 			},
+			end = match (val.end) {
+			case null =>
+				yield null;
+			case let v: *value =>
+				yield alloc(value_dup(v));
+			},
 		};
 	case let val: string =>
 		return strings::dup(val): string;
diff --git a/interp/value.ha b/interp/value.ha
index 1ac8653..04299d5 100644
--- a/interp/value.ha
+++ b/interp/value.ha
@@ -81,7 +81,36 @@ export fn expand(state: *state, val: *ast::value, glob: bool) (value | error) =
 				return value_dup(&x[ix]);
 			};
 		case access_type::SLICE =>
-			abort(); // TODO
+			const ix = expand(state, val.index as *ast::value, true)?;
+			defer value_finish(&ix);
+			const ix = value_int(&ix)?;
+			if (ix <= 0) {
+				return bounds;
+			};
+			const ix = ix: size - 1;
+
+			const end = expand(state, val.end as *ast::value, true)?;
+			defer value_finish(&end);
+			const end = value_int(&end)?;
+			if (end <= -1) {
+				return bounds;
+			};
+			const end = end: size - 1;
+
+			match (var.value) {
+			case let x: str =>
+				if (ix >= len(x)) {
+					return bounds;
+				};
+				const sub = strings::sub(x, ix, end);
+				return strings::dup(sub);
+			case let x: []value =>
+				if (ix >= len(x)) {
+					return bounds;
+				};
+				let v: value = if (end == -1) x[ix..] else x[ix..end];
+				return value_dup(&v);
+			};
 		};
 	case let val: []*ast::value =>
 		let list: []value = alloc([], len(val));
diff --git a/parse/value.ha b/parse/value.ha
index bff0372..0bc2d83 100644
--- a/parse/value.ha
+++ b/parse/value.ha
@@ -5,6 +5,7 @@ use lex::{ltok};
 use io;
 use strings;
 use strconv;
+use fmt;
 
 // Parses a list of values.
 export fn parse_value_list(p: *parser, lf: bool) ([]*ast::value | error) = {
@@ -133,12 +134,36 @@ fn parse_access(p: *parser) (ast::access | error) = {
 		atype = atype,
 		target = strings::dup(var.1),
 		index = null,
+		end = null,
 	};
 
 	if (atype == access_type::VAR && try(p, ltok::LPAREN)? is lex::token) {
-		access.atype = access_type::INDEX;
 		const (ix, _) = parse_value(p)?;
-		access.index = alloc(ix);
+		let arg: str = match (ix) {
+		case let arg: ast::argument =>
+			yield arg;
+		case =>
+			yield "";  // ix is not a range
+		};
+		if (strings::contains(arg, '-')) {
+			access.atype = access_type::SLICE;
+
+			let tokens = strings::tokenize(arg, "-");
+			let start = strings::next_token(&tokens) as str;
+			if (start == "") {
+				start = "1"; // start with first value
+			};
+			access.index = alloc(strings::dup(start): ast::string: ast::value);
+
+			let end = strings::remaining_tokens(&tokens);
+			if (end == "") {
+				end = "0"; // "open end"
+			};
+			access.end = alloc(strings::dup(end): ast::string: ast::value);
+		} else {
+			access.atype = access_type::INDEX;
+			access.index = alloc(ix);
+		};
 		want(p, ltok::RPAREN)?;
 	};
 
diff --git a/test/access.rc b/test/access.rc
index 5b24cea..1f58110 100644
--- a/test/access.rc
+++ b/test/access.rc
@@ -37,6 +37,28 @@ begin "Quoted access"
 }
 end
 
-# TODO: Test slices
+begin "List slice access"
+@{
+	x=(1 2 3 4 5)
+	y=$x(2-4)
+	test $"y "=" "2 3" || fail 'expected $"x(2-4) to equal "2 3"'

Drew DeVault <sir@cmpwn.com>

a month ago

The upper value should be inclusive, so this should print 2 3 4.

+
+	y=$x(2-)
+	test $"y "=" "2 3 4 5" || fail 'expected $"x(2-) to equal "2 3 4 5"'
+
+	y=$x(-4)
+	test $"y "=" "1 2 3" || fail 'expected $"x(-4) to equal "1 2 3"'
+
+	x="ABCDE"
+	y=$x(2-4)
+	test $y "=" "BC" || fail 'expected $x(2-4) to equal "BC"'
+
+	y=$x(2-)
+	test $y "=" "BCDE" || fail 'expected $x(2-) to equal "BCDE"'
+
+	y=$x(-4)
+	test $y "=" "ABC" || fail 'expected $x(-4) to equal "ABC"'
+}
+end
 
 finish
-- 
2.42.0

Drew DeVault <sir@cmpwn.com>

a month ago

Great work! Just one nit: