Convert numeric strings to numbers for output

classes/local/evaluator.php

@@ -163,6 +163,13 @@ public function substitute_variables_in_text(string $text, bool $skiplists = tru
                 if ($skiplists && in_array($result->type, [token::LIST, token::SET])) {
                     continue;
                 }
+                // If the result is a numeric string, we convert it back to a number, in order for
+                // the standard PHP formatting to apply: numbers with an absolute value ≥ 1e14
+                // or < 0.0001 would normally be printed in scientific notation.
+                if ($result->type === token::STRING && is_numeric($result->value)) {
+                    $result->type = token::NUMBER;
+                    $result->value = floatval($result->value);
+                }
                 // If the result is a number, we try to localize it, unless the admin settings do not
                 // allow the decimal comma.
                 if ($result->type === token::NUMBER) {

tests/evaluator_test.php

@@ -1348,6 +1348,33 @@ public function test_substitute_variables_in_text(): void {
         self::assertEquals($expected, $output);
     }
 
+    public function test_substitute_variables_in_text_with_sigfig(): void {
+        $this->resetAfterTest();
+        $this->setAdminUser();
+
+        // Define, parse and evaluate some variables.
+        $vars = 'a=0.3; b=sigfig(a, 2); c=0.000005; d=sigfig(c, 8); e=fact(19); f=sigfig(e, 3)';
+        $parser = new parser($vars);
+        $statements = $parser->get_statements();
+        $evaluator = new evaluator();
+        $evaluator->evaluate($statements);
+
+        // We only test the correct replacement of the numbers; correct interpretation of
+        // placeholders is covered in another test.
+        $text = '{a} -- {b} -- {c} -- {d} -- {e} -- {f}';
+        $output = $evaluator->substitute_variables_in_text($text);
+        $expected = '0.3 -- 0.3 -- 5.0E-6 -- 5.0E-6 -- 1.2164510040883E+17 -- 1.22E+17';
+        self::assertEquals($expected, $output);
+
+        // Setting the localised decimal separator, but disallow the decimal comma in the admin settings.
+        qtype_formulas_test_helper::define_local_decimal_separator();
+        set_config('allowdecimalcomma', 1, 'qtype_formulas');
+        self::assertEquals('1', get_config('qtype_formulas', 'allowdecimalcomma'));
+        $output = $evaluator->substitute_variables_in_text($text);
+        $expected = '0,3 -- 0,3 -- 5,0E-6 -- 5,0E-6 -- 1,2164510040883E+17 -- 1,22E+17';
+        self::assertEquals($expected, $output);
+    }
+
     public function test_substitute_variables_in_algebraic_formula(): void {
         // Define, parse and evaluate some variables.
         $vars = 'a=1; b=[2,3,4]; c={1,2,3}; x={1:10}; y={1:10}; k = [[1,2],[3,4]];';

tests/renderer_test.php

@@ -288,6 +288,33 @@ public function test_substitution_of_local_variables(): void {
         $this->check_output_does_not_contain_stray_placeholders();
     }
 
+    public function test_right_answer_feedback_uses_appropriate_decimal_separator(): void {
+        // Setting the localised decimal separator, but disallow the decimal comma in the admin settings.
+        qtype_formulas_test_helper::define_local_decimal_separator();
+        self::assertEquals('0', get_config('qtype_formulas', 'allowdecimalcomma'));
+
+        $q = $this->get_test_formulas_question('testsinglenum');
+        $q->parts[0]->answer = '3.5';
+
+        $this->start_attempt_at_question($q, 'immediatefeedback', 1);
+        $this->process_submission(['0_0' => '42', '-submit' => 1]);
+        $this->check_output_contains_lang_string('correctansweris', 'qtype_formulas', '3.5');
+
+        // Now allowing the decimal comma to be used.
+        set_config('allowdecimalcomma', 1, 'qtype_formulas');
+        $this->start_attempt_at_question($q, 'immediatefeedback', 1);
+        $this->process_submission(['0_0' => '42', '-submit' => 1]);
+        $this->check_output_contains_lang_string('correctansweris', 'qtype_formulas', '3,5');
+
+        // Make sure the decimal comma is also applied for numbers that are string tokens.
+        // Note that we *should* have 3,50 as the model answer, but as we are converting
+        // the string output from sigfig() back to a number, trailing zeroes will be lost.
+        $q = $this->get_test_formulas_question('testsinglenum');
+        $q->parts[0]->answer = 'sigfig(3.5, 3)';
+        $this->process_submission(['0_0' => '42', '-submit' => 1]);
+        $this->check_output_contains_lang_string('correctansweris', 'qtype_formulas', '3,5');
+    }
+
     public function test_render_question_with_separate_unit_field(): void {
         $q = $this->get_test_formulas_question('testsinglenumunitsep');
         $q->parts[0]->unitpenalty = 0.5;