Function getElement

src/compute-engine/library/linear-algebra.ts:1891–1900

* Get element from matrix at 1-based indices

(
  M: Expression,
  i: number,
  j: number,
  ce: ComputeEngine
)

        // Interpret a vector as a 1×n matrix (linear form), as `Kernel` does.
        const rowCount = shape.length === 1 ? 1 : shape[0];
        const columnCount = shape.length === 1 ? shape[0] : shape[1];

        // Exact path: for an exact integer/rational matrix, the rank is the
        // number of pivots in the exact RREF (no tolerance ambiguity).
        const rationalMatrix = tensorToRationalMatrix(
          op,
          rowCount,
          columnCount
        );
        if (rationalMatrix) {
          const { pivotCols } = exactRationalRref(rationalMatrix);
          return ce.number(pivotCols.length);