Transcript Paradigms

Paradigms
• Imperative
• Functional
• Object-Oriented
• Rule-Based
• Logic
• Visual*
• Scripting*
* whether visual and scripting methodologies are
paradigms is debatable.
CSE 341 -- S. Tanimoto
Paradigms
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Paradigm
General style of thinking that underlies a
programming language
Webster’s New World Dictionary: “a pattern,
example, or model”.
Imperative
Rule-based
Functional
Logic
Object-oriented
Visual data-flow
Scripting
CSE 341 -- S. Tanimoto
Paradigms
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The Imperative Paradigm
An imperative program is a sequence of commands
Read a value from a file.
Evaluate an arithmetic expression.
Assign a value to a variable.
Test a condition and branch if it is true.
Iterate a loop body until a condition is false.
Print a value onto the screen.
CSE 341 -- S. Tanimoto
Paradigms
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The Functional Paradigm
An functional program is a collection of function definitions
and function applications.
Define SQR(x): {
Apply the * function to x and x}
Apply SQR to 7;
CSE 341 -- S. Tanimoto
Paradigms
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The Object-Oriented Paradigm
An object-oriented program is a collection of object class
definitions, in which both data members and methods are
specified.
Class Student extends Person {
int student_number;
int get_student_number() { return student_number; }
int set_student_number (int num) {
student_number = num;
}
CSE 341 -- S. Tanimoto
Paradigms
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The Rule-Based Paradigm
A rule-based program is a collection of if-then rules.
if name = "" then input name;
if name starts with "A" then print "Early in the
alphabet";
CSE 341 -- S. Tanimoto
Paradigms
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The Logic-Programming
Paradigm
A logic program is a collection of logical propositions and
questions.
If x is a bird or an airplane, then x has wings.
Tweety is a bird.
Does Tweety have wings?
CSE 341 -- S. Tanimoto
Paradigms
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The Visual Data-Flow Paradigm
A visual data-flow program is a diagram in which boxes
represent operations and arrows indicate the flow of data
from outputs of operations to inputs of other operations.
3x2 + 5x + 8
3
*
*
input
x
+
*
+
5
8
CSE 341 -- S. Tanimoto
Paradigms
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The Scripting Paradigm*
A script is a relatively small program that serves to direct
activities of a system, typically by calling upon system
services and programs written in other languages.
Fetch input parameters from the environment.
Authenticate the user against a username/password
database.
Issue a database query.
Format the results as a web page.
Print the web page to the standard output stream.
CSE 341 -- S. Tanimoto
Paradigms
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Comparing Paradigms
Imperative : actions can be broken down into sequences of
commands. State of the computation may be very important in
thinking about the program.
Functional: the program can be specified in terms of a
collection of input-output relationships.
Rule-based: the computation is best described in terms of
matching patterns in the data, and then taking appropriate
actions for each pattern.
Logic: the problem and solution can be described using
mathematical logic.
CSE 341 -- S. Tanimoto
Paradigms
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Comparing Paradigms (Cont)
Object-oriented: the components of a system can be
organized as objects -- really “agents” than encapsulate data
and know how to perform methods on that data.
Visual data-flow: the computation can be laid out as a
network of processing stations with paths that carry data from
one to another.
Scripting: the problem is to control a collection of higher-level
capabilities already written, possibly in other languages.
Scripting is like glueing various services together to create new
ones or automate a sequence of program invocations that
would otherwise be done manually.
CSE 341 -- S. Tanimoto
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Rapid Prototyping vs Product
Development
Rapid prototyping: full product specifications typically
unavailable. Minor bugs may not be a problem. Programmer
time is of the essence. Early semantic feedback emphasized
above thorough error checking. High-level features (e.g.,
garbage collection, infinite-precision integers) that remove
burdens from the programmer are prominent, even if they slow
performance.
Product development: product specification is complete or
almost complete. Bugs will be highly embarrassing or worse.
Compilers with strict type checking and the use of test
protocols are prominent. Correct adherence to spec is very
important, as is maintainability of code. Code optimization for
performance is often an issue.
CSE 341 -- S. Tanimoto
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