Implement grammar parser

This implements the grammar struct together with
some other helpful structures like char-set and character.

The grammar struct parses a grammar file and also generates
the FIRST and FOLLOWS tables.

1 files changed, 90 insertions, 0 deletions

diff --git a/src/char-set.zig b/src/char-set.zig
new file mode 100644
index 0000000..d244540
--- /dev/null
+++ b/src/char-set.zig
@@ -0,0 +1,90 @@
+const std = @import("std");
+
+const Character = @import("character.zig").Character;
+
+const Self = @This();
+
+charset: [256]bool = std.mem.zeroes([256]bool),
+
+pub inline fn is_set(self: *const Self, c: usize) bool {
+	return self.charset[c];
+}
+
+pub inline fn set(self: *Self, c: usize) void {
+	self.charset[c] = true;
+}
+
+pub inline fn reset(self: *Self, c: usize) void {
+	self.charset[c] = false;
+}
+
+pub inline fn set_if(self: *Self, c: usize, flag: bool) void {
+	self.charset[c] = self.charset[c] or flag;
+}
+
+pub fn format(
+	self: *const Self,
+	comptime fmt: []const u8,
+	options: std.fmt.FormatOptions,
+	writer: anytype,
+) !void {
+	_ = fmt;
+	_ = options;
+
+	try writer.print("{{ ", .{});
+
+	for (self.charset, 0..) |is_first, index| {
+		if (is_first) {
+			if (index == Character.EPSILON) {
+				try writer.print("{} ", .{Character { .epsilon = void{} }});
+			} else if (index == Character.END) {
+				try writer.print("$ ", .{});
+			} else {
+				try writer.print("'{c}' ", .{@as(u8, @truncate(index))});
+			}
+		}
+	}
+
+	try writer.print("}}", .{});
+}
+
+pub fn expect(self: *const Self, expected: []const u8) !void {
+	var matrix = std.mem.zeroes([255]bool);
+
+	for (expected) |c| {
+		matrix[c] = true;
+	}
+
+	for (matrix, 0..) |contained, index| {
+		if (self.is_set(index) != contained) {
+			std.debug.print("expected {{ ", .{});
+
+			for (expected) |c| {
+				if (c == Character.EPSILON) {
+					std.debug.print("{} ", .{Character { .epsilon = void{} }});
+				} else if (c == Character.END) {
+					std.debug.print("$ ", .{});
+				} else {
+					std.debug.print("'{c}' ", .{c});
+				}
+			}
+
+			std.debug.print("}} but got {} (", .{self});
+
+			if (index == Character.EPSILON) {
+				std.debug.print("{}", .{Character { .epsilon = void{} }});
+			} else if (index == Character.END) {
+				std.debug.print("$", .{});
+			} else {
+				std.debug.print("'{c}'", .{@as(u8, @truncate(index))});
+			}
+			if (contained) {
+				std.debug.print(" missing)\n", .{});
+			} else {
+				std.debug.print(" not expected)\n", .{});
+			}
+
+			return error.ExpectEqualError;
+		}
+	}
+}