@jahed/sparql-engine/dist/operators/sparql-filter.js

SPARQL query engine for servers and web browsers.

import { Pipeline } from "../engine/pipeline/pipeline.js";
import { SPARQLExpression, } from "./expressions/sparql-expression.js";
import { Bindings } from "../rdf/bindings.js";
import { literalIsBoolean, termIsLiteral, termToValue } from "../utils/rdf.js";
/**
 * Evaluate SPARQL Filter clauses
 * @see {@link https://www.w3.org/TR/sparql11-query/#expressions}
 * @param source - Input {@link PipelineStage}
 * @param expression - FILTER expression
 * @param customFunctions - User-defined SPARQL functions (optional)
 * @return A {@link PipelineStage} which evaluate the FILTER operation
 */
export default function sparqlFilter(source, expression, customFunctions) {
    const expr = new SPARQLExpression(expression, customFunctions);
    return Pipeline.getInstance().filterAsync(source, async (bindings) => {
        const result = await expr.evaluate(bindings);
        if (result &&
            "datatype" in result &&
            termIsLiteral(result) &&
            literalIsBoolean(result)) {
            return termToValue(result);
        }
        return false;
    });
}
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