Function parser_validateAndParsePauliStrSum

quest/src/core/parser.cpp:500–531

PauliStrSum parser_validateAndParsePauliStrSum(string lines, bool rightIsLeastSignificant, const char* caller) {
    assertStringIsValidPauliStrSum(lines, caller);

    // allocate space for as many strings as there are lines, though we might collect fewer (we skip empty lines)
    qindex numLines = getNumLines(lines);
    vector<qcomp>    coeffs;   coeffs.reserve(numLines);
    vector<PauliStr> strings; strings.reserve(numLines);
    
    // parse each line in-turn
    stringstream stream(lines);
    for (string line; getline(stream, line); ) {

        // skip empty lines
        if (isOnlyWhiteSpace(line))
            continue;

        qcomp coeff;
        PauliStr string;
        parseWeightedPaulis(line, coeff, string, rightIsLeastSignificant); // validates

        coeffs.push_back(coeff);
        strings.push_back(string);
    }

    // invoke other API function, which will run additional validation (e.g. checking
    // memory allocations succeeded) and may fail, reporting that 'createPauliStrSum()'
    // failed, rather than caller. That's a minor, acceptable evil. Furthermore, this
    // call creates new memory alongside our existing vectors, meaning total memory
    // is temporarily double than that which is strictly necessary; also acceptable.
    PauliStrSum out = createPauliStrSum(strings, coeffs);
    return out;
}