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MDL-60431 qtype_calculated: handle NAN and INF calculation outcomes

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With significant-digits presentation mode, NAN would be formatted as
'NAN' followed by zeroes, which looks silly, and +INF would cause an
execution timeout as Moodle tries to divide +∞ by 10 until it becomes
less than 1, which can happen in a divide-by-zero situation.

Note that the user can't answer NAN or INF to any question, but at this
at least now looks consistent and also doesn't break Moodle in the case
of +INF.
This commit is contained in:
Jonathon Fowler 2021-05-05 16:35:52 +10:00
parent efb3d4e7a7
commit be65ee093d
4 changed files with 31 additions and 1 deletions
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6
question/type/calculated/question.php
View File

@ -335,7 +335,11 @@ class qtype_calculated_variable_substituter {
* @return string formtted number.
*/
public function format_float($x, $length = null, $format = null) {
if (!is_null($length) && !is_null($format)) {
if (is_nan($x)) {
$x = 'NAN';
} else if (is_infinite($x)) {
$x = ($x < 0) ? '-INF' : 'INF';
} else if (!is_null($length) && !is_null($format)) {
if ($format == '1' ) { // Answer is to have $length decimals.
// Decimal places.
$x = sprintf('%.' . $length . 'F', $x);

3
question/type/calculated/questiontype.php
View File

@ -1857,6 +1857,9 @@ function qtype_calculated_calculate_answer($formula, $individualdata,
// Something went wrong, so just return NaN.
$calculated->answer = NAN;
return $calculated;
} else if (is_nan($answer) || is_infinite($answer)) {
$calculated->answer = $answer;
return $calculated;
}
if ('1' == $answerformat) { // Answer is to have $answerlength decimals.
// Decimal places.

15
question/type/calculated/tests/questiontype_test.php
View File

@ -238,4 +238,19 @@ class qtype_calculated_test extends advanced_testcase {
</pre>
'));
}
public function test_calculate_answer_nan_inf() {
$answer = qtype_calculated_calculate_answer('acos(1.1)', [], 0.1, 1, 2, 2);
$this->assertIsObject($answer);
$this->assertNan($answer->answer);
$answer = qtype_calculated_calculate_answer('log(0.0)', [], 0.1, 1, 2, 2);
$this->assertIsObject($answer);
$this->assertInfinite($answer->answer); // Actually -INF.
// Dividing by zero is hard to test, so get +INF another way.
$answer = qtype_calculated_calculate_answer('abs(log(0.0))', [], 0.1, 1, 2, 2);
$this->assertIsObject($answer);
$this->assertInfinite($answer->answer);
}
}

8
question/type/calculated/tests/variablesubstituter_test.php
View File

@ -134,4 +134,12 @@ class qtype_calculated_variable_substituter_test extends advanced_testcase {
$this->assertSame('0,12', $vs->format_float(0.12345, 2, 2));
$this->assertSame('0,0012', $vs->format_float(0.0012345, 4, 1));
}
public function test_format_float_nan_inf() {
$vs = new qtype_calculated_variable_substituter([ ], '.');
$this->assertSame('NAN', $vs->format_float(NAN));
$this->assertSame('INF', $vs->format_float(INF));
$this->assertSame('-INF', $vs->format_float(-INF));
}
}