Introduction to Programming 1
... What is programming?
• program: set of instructions
to be carried out by a computer; an
example of software
• program execution: act of
carrying out the instructions
contained in a program
• programming language: systematic set of rules used to
describe computations in a format that is editable by ...
... • We can think of programs, procedures, and
functions in a programming language as all being
represented by the mathematical concept of a
• In mathematics there is no concept of memory
location, or values of variables, so that an
assignment statement such as x = x + 1 makes
no sense in fun ...
... • The youthful Professor Sheard
... – syntax of a real number
– T, meaning true
– F, meaning false
– ϕ, the symbol representing the empty list
Formalizing the Dynamic Semantics of Java
... A PL’s semantics is concerned with the meaning of (wellformed) programs: how a program may be expected to
behave when executed on a computer.
A PL’s pragmatics is concerned with the way in which the
PL is intended to be used in practice. Pragmatics include
the paradigm(s) supported by the PL.
... • Use l-calculus (Church, Curry, etc):
• Or, non-anonymously:
• Currying isomorphism:
... just primitives, are defined as part of the
Other functions can be defined and named by the
Example: (using Scheme, a functional
programming language derived from LISP)
(define (double x)
(* 2 x))
(define (square x)
(* x x))
(define (polynomial x)
(double (square x))
Also calle ...
... o This is the clean part!
• The smaller part:
o Has all the side effects
o Interacts with the user / rest of the world
o This is the dirty part!
... – The notions of variable, assignment and (non
recursive) looping are NOT part of the ‘pure’
functional programming model
• Functional paradigm seen by some as a more reliable
paradigm for software design than the imperative
Functional and Imperative Programming
... This perhaps gets a list of (first name, last name) globalvar between calls as well? Hopefully you can
pairs from a database. But note how we haven’t see that modelling this function as a black box
said how this should be done: the statement is with a single output can’t work. So pure functional lan ...
... o Increased ability to learn new languages
Computer programming is rapidly changing
Programmers must know and understand the vocabulary and
concepts of programming languages to learn new languages as
they are developed.
o Better understanding of the significance of implementation
Allows the pr ...
... problems this way and not notice.
For another reason we need only look at how programming problems are stated in programming courses. We use types not logical formulas. Moreover, as we will stress in this course,
the language of types subsumes logic. Indeed it goes well beyond it. Also, types make i ...
... influences are from Lisp. Lisp has a definite execution order, and has support for
assignable local variables. The design of functional languages has focused on their
correctness in an abstract sense, without a focus on actual programming. This gives them
an often unapproachable reputation as langua ...
Why study programming languages?
... Design specification
• Programming environment - external support for the
Debugger, syntax-directed editor
Supporting function, platforms
Supporting all the software lifecycle phases
... – denoted by /f
– depends on one function with a number of
COP4020 Homework Assignment 2
... 2. Explain the difference between a functional and a special form in Scheme.
3. We can implement a binary tree data structure by using lists with three elements:
(value left-tree right-tree) as shown in class. A leaf is an empty list. Given the
PPT - University of Virginia, Department of Computer Science
... – CLU - first to demo utility of data abstraction
– FP - functional languages come into being.
– CSP - clarified many communication/ synchronization issues in
– Ada - whether of not you like it, it's a significant accomplishment
– Logo - computing for children is possible
– Mesa - sta ...
... state changes during program execution
In computer science, functional programming is a programming paradigm—a style of building the structure and elements of computer programs—that treats computation as the evaluation of mathematical functions and avoids changing-state and mutable data. It is a declarative programming paradigm, which means programming is done with expressions. In functional code, the output value of a function depends only on the arguments that are input to the function, so calling a function f twice with the same value for an argument x will produce the same result f(x) each time. Eliminating side effects, i.e. changes in state that do not depend on the function inputs, can make it much easier to understand and predict the behavior of a program, which is one of the key motivations for the development of functional programming.Functional programming has its roots in lambda calculus, a formal system developed in the 1930s to investigate computability, the Entscheidungsproblem, function definition, function application, and recursion. Many functional programming languages can be viewed as elaborations on the lambda calculus. Another well-known declarative programming paradigm, logic programming, is based on relations.In contrast, imperative programming changes state with commands in the source language, the most simple example being assignment. Imperative programming does have functions—not in the mathematical sense—but in the sense of subroutines. They can have side effects that may change the value of program state. Functions without return values therefore make sense. Because of this, they lack referential transparency, i.e. the same language expression can result in different values at different times depending on the state of the executing program.Functional programming languages, especially purely functional ones such as Hope and Rex, have largely been emphasized in academia rather than in commercial software development. However, prominent functional programming languages such as Common Lisp, Scheme, Clojure, Wolfram Language (also known as Mathematica), Racket, Erlang, OCaml, Haskell, and F# have been used in industrial and commercial applications by a wide variety of organizations. Functional programming is also supported in some domain-specific programming languages like R (statistics), J, K and Q from Kx Systems (financial analysis), XQuery/XSLT (XML), and Opal. Widespread domain-specific declarative languages like SQL and Lex/Yacc use some elements of functional programming, especially in eschewing mutable values.Programming in a functional style can also be accomplished in languages that are not specifically designed for functional programming. For example, the imperative Perl programming language has been the subject of a book describing how to apply functional programming concepts. This is also true of the PHP programming language. C# 3.0 and Java 8 added constructs to facilitate the functional style. The Julia language also offers functional programming abilities. An interesting case is that of Scala – it is frequently written in a functional style, but the presence of side effects and mutable state place it in a grey area between imperative and functional languages.