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[FEATURE] Add generate_series(start,stop,step) expression function

The function creates an array containing a sequence of numbers.
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nirvn committed Aug 20, 2018
1 parent cc5e0e1 commit 3c3cc43010fe919c9821bcfdb1a0b2d94ab9abeb
@@ -0,0 +1,13 @@
{
"name": "generate_series",
"type": "function",
"description": "Creates an array containing a sequence of numbers.",
"arguments": [
{"arg":"start", "description":"first value of the sequence"},
{"arg":"stop", "description":"value that ends the sequence once reached"},
{"arg":"step","optional":true,"default":"1","description":"value used as the increment between values"}
],
"examples": [ { "expression":"generate_series('1,5)", "returns":"array: '1', '2', '3', '4', '5'"},
{ "expression":"generate_series('5,1,-1)", "returns":"array: '5', '4', '3', '2', '1'"}
]
}
@@ -220,6 +220,30 @@ bool QgsExpressionFunction::allParamsStatic( const QgsExpressionNodeFunction *no
return true;
}

static QVariant fcnGenerateSeries( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
double start = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
double stop = QgsExpressionUtils::getDoubleValue( values.at( 1 ), parent );
double step = QgsExpressionUtils::getDoubleValue( values.at( 2 ), parent );

if ( step == 0.0 || ( step > 0.0 && start > stop ) || ( step < 0.0 && start < stop ) )
return QVariant();

QVariantList array;
int length = 1;

array << start;
double current = start + step;
while ( ( ( step > 0.0 && current <= stop ) || ( step < 0.0 && current >= stop ) ) && length <= 1000000 )
{
array << current;
current += step;
length++;
}

return array;
}

static QVariant fcnGetVariable( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction * )
{
if ( !context )
@@ -4724,6 +4748,7 @@ const QList<QgsExpressionFunction *> &QgsExpression::Functions()
<< new QgsStaticExpressionFunction( QStringLiteral( "array_distinct" ), 1, fcnArrayDistinct, QStringLiteral( "Arrays" ) )
<< new QgsStaticExpressionFunction( QStringLiteral( "array_to_string" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "array" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "delimiter" ), true, "," ) << QgsExpressionFunction::Parameter( QStringLiteral( "emptyvalue" ), true, "" ), fcnArrayToString, QStringLiteral( "Arrays" ) )
<< new QgsStaticExpressionFunction( QStringLiteral( "string_to_array" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "string" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "delimiter" ), true, "," ) << QgsExpressionFunction::Parameter( QStringLiteral( "emptyvalue" ), true, "" ), fcnStringToArray, QStringLiteral( "Arrays" ) )
<< new QgsStaticExpressionFunction( QStringLiteral( "generate_series" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "start" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "stop" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "step" ), true, 1.0 ), fcnGenerateSeries, QStringLiteral( "Arrays" ) )

//functions for maps
<< new QgsStaticExpressionFunction( QStringLiteral( "map" ), -1, fcnMap, QStringLiteral( "Maps" ) )
@@ -2607,6 +2607,23 @@ class TestQgsExpression: public QObject
QCOMPARE( v4, QVariant( "test value" ) );
}

void eval_generate_series()
{
QVariantList array;
array << 1 << 2 << 3 << 4;
QCOMPARE( QgsExpression( "generate_series(1,4)" ).evaluate(), QVariant( array ) );
array.clear();
array << 1 << 1.25 << 1.5 << 1.75 << 2;
QCOMPARE( QgsExpression( "generate_series(1,2,0.25)" ).evaluate(), QVariant( array ) );
array.clear();
array << 10 << 9 << 8;
QCOMPARE( QgsExpression( "generate_series(10,8,-1)" ).evaluate(), QVariant( array ) );

QCOMPARE( QgsExpression( "generate_series(10,11,-1)" ).evaluate(), QVariant() );
QCOMPARE( QgsExpression( "generate_series(10,5)" ).evaluate(), QVariant() );
QCOMPARE( QgsExpression( "generate_series(1,2,0)" ).evaluate(), QVariant() );
}

void eval_string_array()
{
QgsFeature f( 100 );

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