Drew Wyborski Programming Languages ML: the metalanguage Drew Wyborski Programming Languages

Introduction Originally conceived to develop proof tactics Automatically infers types Focus on developing programs through a logical approach Used as the basis for several other languages and dialects

Functional Programming Logical analysis is simple and easy No reassignment or modification of types Can prove assertions about a program with ease Difficult to write programs that are illogical Lend themselves well of parallel execution Still retain all the useful components of a traditional language

Functional vs. Imperative Development Cycle Development Language Run-time System FORTRAN, Pascal, C ML, Hope, Lisp

Language Overview Call-by-value evaluation strategy Automatic memory allocation through garbage collection Parametric polymorphism Static typing Exception handling Pattern matching

Development and Creation Developed by Robin Milner in 1973 at Edinburgh University The goal behind ML The perfect language

Standard ML Standard ML ’90 & Standard ML ‘97 Changes from original Edinburgh ML Standard ML-New Jersey Other popular versions Moscow ML ML Kit MLton PolyML

Characteristics Safety through the type-checker Structures and signatures Flexibility of functions Call-by-value evaluation Polymorphism Compile-time type checking Type inference

Characteristics Garbage collection Exemption handling Immutable data types Updating references Abstraction Parametric modules Formal definition Proof of completeness

Data Type/Operators Operators and types similar to C++/Java int, string, bool and real remain the same Operators have slight differences Additional Boolean types are included showing the rational/logical basis andalso & orelse

Syntax Input is placed into user’s implementation Machine responds with result of expression Specified layout for entry and output 3 + 4; val it = 7 : int If an error is made in entry, the machine responds with an appropriate error The unit data type

Definitions Global constants Functions Extensions val PI = 3.4; Help increase readability Functions fun succ n = n+1; val succ = fn : int  int Extensions if…then…else functions Multiple input/output functions