Edited sentence: Also Macsyma's matrices were implemented as lists of lists, which cost another factor of perhaps 5-10 in speed for key algorithms.At MIT Macsyma had a link to the IMSL (now Rogue Wave Software) numerical libraries, but this link was severed when Macsyma moved to Symbolics.Double precision arithmetic in Macsyma (on a PC version) was about six times slower than Fortran.Lisp developers at Symbolics generally believed that numerical analysis was an old technology that was not important for Lisp applications, so they declined to invest in it.Macsyma did not have many of the basic algorithms of numerical linear algebra, such as LU decomposition.Mastering symbolic math was a herculean task; but numerical capabilities were critical to get a piece of the much larger engineering and lower-end scientific markets.The greatest product weakness of Macsyma was its numerical analysis