Real0: TYPE = REAL ← 0;

Catch the signal Real.RealException to detect singular or unstable systems, e.g.,

singular: BOOLEAN ← FALSE;

x ← Matrix.Invert[A!

IF NOT singular THEN ...

InvalidMatrix, InvalidOperation: SIGNAL;

VecSeq: TYPE = RECORD[SEQUENCE ncols: INTEGER OF Real0];

RowN: TYPE = REF VecSeq;

MatrixSeq: TYPE = RECORD[SEQUENCE nrows: INTEGER OF RowN];

MatrixN: TYPE = REF MatrixSeq;

ColumnN: TYPE = REF VecSeq;

Invert: PROCEDURE [a: MatrixN] RETURNS [ai: MatrixN];

Determinant: PROC[a: MatrixN] RETURNS [det: REAL];

Transpose: PROCEDURE [a: MatrixN] RETURNS [transpose: MatrixN];

Multiply: PROCEDURE [a: MatrixN, b: MatrixN] RETURNS [c: MatrixN];

MultiplyVec: PROC[a: MatrixN, v: ColumnN] RETURNS [c: RowN];

Create: PROC [nrows, ncols: INTEGER] RETURNS [a: MatrixN];

END.