smlnj binary package in Ubuntu Bionic i386

 SML/NJ is an implementation of the Standard ML programming language.
 Standard ML has many features, including type safety, polymorphism,
 algebraic data types with pattern matching, higher-order functions,
 and a sophisticated module system. It is especially well-suited for
 writing compilers and other language processors.
 .
 This package includes the interactive compiler (sml), the compilation
 manager (CM), and some essential libraries. It is a "working"
 version, but believed to be stable.
 .
 Install this package if you want to program in SML.

Source package