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const std = @import("std");
const Grammar = @import("grammar.zig");
const NonTerminal = @import("non-terminal.zig");
const Character = @import("character.zig").Character;
const Generator = @import("generator.zig").Generator;
const gss = @import("gss.zig");
const State = struct {
const Self = @This();
name: u8,
rule: NonTerminal.Rule,
inner_position: usize,
input_position: usize,
pub fn format(
self: *const Self,
comptime fmt: []const u8,
options: std.fmt.FormatOptions,
writer: anytype,
) !void {
_ = fmt;
_ = options;
try writer.print("[ {c}, {s}, {}, {} ]", .{
self.name,
self.rule,
self.inner_position,
self.input_position,
});
}
};
pub fn check(grammar: *Grammar, input: []const u8, allocator: std.mem.Allocator) !bool {
var stacks = std.ArrayList(std.ArrayList(State)).init(allocator);
defer {
for (stacks.items) |stack| {
stack.deinit();
}
stacks.deinit();
}
const entry = grammar.entry_point();
for (entry.rules()) |rule| {
const state = State {
.name = entry.name,
.rule = rule,
.inner_position = 0,
.input_position = 0,
};
var stack = std.ArrayList(State).init(allocator);
try stack.append(state);
try stacks.append(stack);
}
var remove_queue = std.ArrayList(usize).init(allocator);
defer remove_queue.deinit();
var add_queue = std.ArrayList(std.ArrayList(State)).init(allocator);
defer add_queue.deinit();
while (stacks.items.len > 0) {
for (stacks.items, 0..) |*stack, stack_index| {
var state: *State = &stack.items[stack.items.len - 1];
if (state.inner_position == state.rule.len) {
if (
stack.items.len == 1 and
state.name == entry.name and
state.input_position == input.len
) {
return true;
}
const old_state = stack.pop();
if (stack.items.len > 0) {
state = &stack.items[stack.items.len - 1];
state.inner_position += 1;
state.input_position = old_state.input_position;
} else {
try remove_queue.append(stack_index);
}
continue;
}
const epsilon_only = state.input_position == input.len;
switch (state.rule[state.inner_position]) {
.terminal => |t| {
if (!epsilon_only and input[state.input_position] == t) {
state.inner_position += 1;
state.input_position += 1;
} else {
try remove_queue.append(stack_index);
}
},
.non_terminal => |n| {
const non_terminal = grammar.non_terminal_by_name(n);
const rules = non_terminal.rules();
if (!epsilon_only and non_terminal.first.is_set(input[state.input_position])) {
for (rules) |rule| {
const next_state = State {
.name = non_terminal.name,
.rule = rule,
.inner_position = 0,
.input_position = state.input_position,
};
var new_stack = try stack.clone();
try new_stack.append(next_state);
try add_queue.append(new_stack);
}
}
if (non_terminal.first.is_set(Character.EPSILON)) {
state.inner_position += 1;
} else {
try remove_queue.append(stack_index);
}
},
.epsilon => {
state.inner_position += 1;
},
}
}
for (remove_queue.items, 0..) |index, offset| {
const stack = stacks.orderedRemove(index - offset);
stack.deinit();
}
for (add_queue.items) |stack| {
try stacks.append(stack);
}
remove_queue.clearAndFree();
add_queue.clearAndFree();
}
return false;
}
test "expr" {
const text =
\\S -> B A
\\A -> + B A
\\A -> _
\\B -> D C
\\C -> * D C
\\C -> _
\\D -> ( S )
\\D -> a
\\D -> b
;
const input = "b+a*b";
const allocator = std.testing.allocator;
var grammar = try Grammar.parse(text, allocator);
defer grammar.deinit(allocator);
try std.testing.expect(try check(&grammar, input, allocator));
}
test "simple 0 - success" {
const text =
\\S -> A S d
\\S -> B S
\\S -> _
\\A -> a
\\A -> c
\\B -> a
\\B -> b
;
const input = "aad";
const allocator = std.testing.allocator;
var grammar = try Grammar.parse(text, allocator);
defer grammar.deinit(allocator);
try std.testing.expect(try check(&grammar, input, allocator));
}
test "simple 0 - fail" {
const text =
\\S -> A S d
\\S -> B S
\\S -> _
\\A -> a
\\A -> c
\\B -> a
\\B -> b
;
const input = "accd";
const allocator = std.testing.allocator;
var grammar = try Grammar.parse(text, allocator);
defer grammar.deinit(allocator);
try std.testing.expect(!try check(&grammar, input, allocator));
}
test "simple 0 - fuzzy" {
const text =
\\S -> A S d
\\S -> B S
\\S -> _
\\A -> a
\\A -> c
\\B -> a
\\B -> b
;
const allocator = std.testing.allocator;
var grammar = try Grammar.parse(text, allocator);
defer grammar.deinit(allocator);
var generator = Generator(struct {
const Self = @This();
pub fn next(_: *Self, n: usize) usize {
return std.crypto.random.uintLessThan(usize, n);
}
}){};
for (0..100) |_| {
const input = try generator.sentential_from_grammar(&grammar, 1000, allocator);
defer allocator.free(input);
try std.testing.expect(try check(&grammar, input, allocator));
}
}
|
