Source : Free On-Line Dictionary of Computing

NPL
     
        1. New Programming Language.  IBM's original (temporary) name
        for PL/I, changed due to conflict with England's "National
        Physical Laboratory."  MPL and MPPL were considered before
        settling on PL/I.  Sammet 1969, p.542.
     
        2. A {functional language} with {pattern matching} designed by
        Rod Burstall and John Darlington in 1977.  The language
        allowed certain sets and logic constructs to appear on the
        right hand side of definitions, E.g.
     
        	setofeven(X) <= <:x: x in X & even(x) :>
     
        The NPL {interpreter} evaluates the list of {generator}s from
        left to right so conditions can mention any bound variables
        that occur to their left.  These were known as {set
        comprehension}s.  NPL eventually evolved into {Hope} but lost
        set comprehensions which were called {list comprehension}s in
        later functional languages.
     
        [John Darlington, "Program Transformation and Synthesis:
        Present Capabilities", Research Report No. 77/43, Dept. of
        Computing and Control, Imperial College of Science and
        Technology, London September 1977.]
     
        3. NonProcedural Language.  A {relational database} language
        developed by T.D. Truitt et al in 1980 for {Apple II} and
        {MS-DOS}.
     
        ["An Introduction to Nonprocedural Languages Using NPL",
        T.D. Truitt et al, McGraw-Hill 1983].