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tutorial_test.dart
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tutorial_test.dart
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import 'dart:math' as math;
import 'package:petitparser/debug.dart';
import 'package:petitparser/petitparser.dart';
import 'package:petitparser/reflection.dart';
import 'package:test/test.dart';
class ExpressionDefinition extends GrammarDefinition {
@override
Parser start() => ref0(term).end();
Parser term() => ref0(add) | ref0(prod);
Parser add() => ref0(prod) & char('+').trim() & ref0(term);
Parser prod() => ref0(mul) | ref0(prim);
Parser mul() => ref0(prim) & char('*').trim() & ref0(prod);
Parser prim() => ref0(parens) | ref0(number);
Parser parens() => char('(').trim() & ref0(term) & char(')').trim();
Parser number() => digit().plusString().trim();
}
class EvaluatorDefinition extends ExpressionDefinition {
@override
Parser add() =>
super.add().castList<num>().map((values) => values[0] + values[2]);
@override
Parser mul() =>
super.mul().castList<num>().map((values) => values[0] * values[2]);
@override
Parser parens() => super.parens().castList<num>().pick(1);
@override
Parser number() => super.number().map((value) => int.parse(value as String));
}
void main() {
test('simple grammar (operators)', () {
final id = letter() & (letter() | digit()).star();
final id1 = id.parse('yeah');
final id2 = id.parse('f12');
expect(id1.value, [
'y',
['e', 'a', 'h']
]);
expect(id2.value, [
'f',
['1', '2']
]);
final id3 = id.parse('123');
expect(id3.message, 'letter expected');
expect(id3.position, 0);
expect(id.accept('foo'), isTrue);
expect(id.accept('123'), isFalse);
expect(
switch (id.parse('foo')) {
Success(value: final value) => 'Success: $value',
Failure(message: final message, position: final position) =>
'Failure at $position: $message',
},
'Success: [f, [o, o]]');
expect(
switch (id.parse('123')) {
Success(value: final value) => 'Success: $value',
Failure(message: final message, position: final position) =>
'Failure at $position: $message',
},
'Failure at 0: letter expected');
});
test('simple grammar (chained calls)', () {
final id = letter().seq(letter().or(digit()).star());
final id1 = id.parse('yeah');
final id2 = id.parse('f12');
expect(id1.value, [
'y',
['e', 'a', 'h']
]);
expect(id2.value, [
'f',
['1', '2']
]);
final id3 = id.parse('123');
expect(id3.message, 'letter expected');
expect(id3.position, 0);
expect(id.accept('foo'), isTrue);
expect(id.accept('123'), isFalse);
});
test('simple grammar (lists)', () {
final id = [
letter(),
[letter(), digit()].toChoiceParser().star()
].toSequenceParser();
final id1 = id.parse('yeah');
final id2 = id.parse('f12');
expect(id1.value, [
'y',
['e', 'a', 'h']
]);
expect(id2.value, [
'f',
['1', '2']
]);
final id3 = id.parse('123');
expect(id3.message, 'letter expected');
expect(id3.position, 0);
expect(id.accept('foo'), isTrue);
expect(id.accept('123'), isFalse);
});
test('simple grammar (typed functions)', () {
final id = seq2(letter(), [letter(), digit()].toChoiceParser().star());
final id1 = id.parse('yeah');
final id2 = id.parse('f12');
expect(
id1.value,
isA<(String, List<String>)>()
.having((sequence) => sequence.$1, 'first', 'y')
.having((sequence) => sequence.$2, 'second', ['e', 'a', 'h']));
expect(
id2.value,
isA<(String, List<String>)>()
.having((sequence) => sequence.$1, 'first', 'f')
.having((sequence) => sequence.$2, 'second', ['1', '2']));
final id3 = id.parse('123');
expect(id3.message, 'letter expected');
expect(id3.position, 0);
expect(id.accept('foo'), isTrue);
expect(id.accept('123'), isFalse);
});
test('different parsers (word)', () {
final id1 = letter() & word().star();
final matches = id1.flatten().allMatches('foo 123 bar4');
expect(matches, ['foo', 'bar4']);
});
test('different parsers (pattern)', () {
final id2 = letter() & pattern('a-zA-Z0-9').star();
final matches = id2.flatten().allMatches('foo 123 bar4');
expect(matches, ['foo', 'bar4']);
});
test('complicated grammar', () {
final term = undefined<Object?>();
final prod = undefined<Object?>();
final prim = undefined<Object?>();
final add = (prod & char('+').trim() & term)
.castList<num>()
.map((values) => values[0] + values[2]);
term.set(add | prod);
final mul = (prim & char('*').trim() & prod)
.castList<num>()
.map((values) => values[0] * values[2]);
prod.set(mul | prim);
final parens =
(char('(').trim() & term & char(')').trim()).map((values) => values[1]);
final number = digit().plus().flatten().trim().map(int.parse);
prim.set(parens | number);
final parser = term.end();
expect(parser.parse('1 + 2 + 3').value, 6);
expect(parser.parse('1 + 2 * 3').value, 7);
expect(parser.parse('(1 + 2) * 3').value, 9);
});
test('expression definition', () {
final parser = ExpressionDefinition().build();
expect(parser.parse('1 + 2 + 3').value, [
'1',
'+',
['2', '+', '3']
]);
expect(parser.parse('1 + 2 * 3').value, [
'1',
'+',
['2', '*', '3']
]);
expect(parser.parse('(1 + 2) * 3').value, [
[
'(',
['1', '+', '2'],
')'
],
'*',
'3'
]);
});
test('evaluator definition', () {
final definition = ExpressionDefinition();
final parser = definition.build();
expect(parser.parse('1 + 2 + 3').value, [
'1',
'+',
['2', '+', '3']
]);
expect(parser.parse('1 + 2 * 3').value, [
'1',
'+',
['2', '*', '3']
]);
expect(parser.parse('(1 + 2) * 3').value, [
[
'(',
['1', '+', '2'],
')'
],
'*',
'3'
]);
});
test('number definition', () {
final definition = EvaluatorDefinition();
final parser = definition.build();
expect(parser.parse('1 + 2 + 3').value, 6);
expect(parser.parse('1 + 2 * 3').value, 7);
expect(parser.parse('(1 + 2) * 3').value, 9);
});
test('number definition', () {
final definition = EvaluatorDefinition();
final parser = definition.buildFrom(definition.number());
expect(parser.parse('42').value, 42);
});
test('expression builder', () {
final builder = ExpressionBuilder<num>();
builder.primitive(digit()
.plus()
.seq(char('.').seq(digit().plus()).optional())
.flatten()
.trim()
.map(num.parse));
builder.group().wrapper(
char('(').trim(), char(')').trim(), (left, value, right) => value);
// Negation is a prefix operator.
builder.group().prefix(char('-').trim(), (operator, value) => -value);
// Power is right-associative.
builder.group().right(
char('^').trim(), (left, operator, right) => math.pow(left, right));
// Multiplication and addition are left-associative, multiplication has
// higher priority than addition.
builder.group()
..left(char('*').trim(), (left, operator, right) => left * right)
..left(char('/').trim(), (left, operator, right) => left / right);
builder.group()
..left(char('+').trim(), (left, operator, right) => left + right)
..left(char('-').trim(), (left, operator, right) => left - right);
final parser = builder.build().end();
expect(parser.parse('-8').value, -8);
expect(parser.parse('1+2*3').value, 7);
expect(parser.parse('1*2+3').value, 5);
expect(parser.parse('8/4/2').value, 1);
expect(parser.parse('2^2^3').value, 256);
});
test('number parsing', () {
final definition = EvaluatorDefinition();
final parser = definition.buildFrom(definition.number());
expect(parser.parse('42').value, 42);
});
test('detect common problems', () {
final definition = EvaluatorDefinition();
final parser = definition.build();
expect(linter(parser), isEmpty);
});
test('debugging parser', () {
final output = <TraceEvent>[];
final parser = letter() & word().star();
trace(parser, output: output.add).parse('f1');
expect(output.map((each) => each.toString()), [
'SequenceParser<dynamic>',
' SingleCharacterParser[letter expected]',
' Success[1:2]: f',
' PossessiveRepeatingParser<String>[0..*]',
' SingleCharacterParser[letter or digit expected]',
' Success[1:3]: 1',
' SingleCharacterParser[letter or digit expected]',
' Failure[1:3]: letter or digit expected',
' Success[1:3]: [1]',
'Success[1:3]: [f, [1]]',
]);
});
}