#Programming_paradigms : #Functional programming
Seeks to use pure functions.
Pure functions:
• have no side effects
• return a value that depends only on their arguments. e.g.
• are easier to reason about and test.
• are more efficient. Once the function has been evaluated for an input, the result can be stored and referred to the next time the function of that input is needed, reducing the number of times the function is called. This is called #memoization.
• are less confusing to run in parallel (See #concurrent programming).
Using only pure functions complicates the otherwise simple task of IO since this appears to inherently require side effects.
Seeks to use pure functions.
Pure functions:
• have no side effects
• return a value that depends only on their arguments. e.g.
sin(x) will, for the same value of x, always return the same result.• are easier to reason about and test.
• are more efficient. Once the function has been evaluated for an input, the result can be stored and referred to the next time the function of that input is needed, reducing the number of times the function is called. This is called #memoization.
• are less confusing to run in parallel (See #concurrent programming).
Using only pure functions complicates the otherwise simple task of IO since this appears to inherently require side effects.
ComputerScientist
#Programming_paradigms : Declarative versus Imperative #Declarative All about relations. Does not state the order in which operations execute. Focuses on what the program should accomplish without specifying how the program should achieve the result. Expresses…
#Programming_paradigms
Expression versus Statement
An expression is a unit of #declarative programming.
A statement is a unit of #imperative programming.
An expression is evaluated whereas a statement is executed.
Expressions
A combination of values, variables and functions that return a value and have no side effects.
Expressions can contain functions and functions may have side effects. A side effect is a change to the abstract state of the running program that does not depend on the function input.
Functional programs do not have assignment statements therefore the value of a variable never changes once defined. An expression is said to be referentially transparent if it can be replaced with its corresponding value without changing the program's behavior. Evaluating a referentially transparent function gives the same value for same arguments. Such functions are called pure functions. Referentially transparent expressions allow #memoization.
Statements
Do not return results and are executed solely for their side effects.
Simple statements:
• assertion
• assignment
• goto
• return
• call
Compound statements: (may contain statements as components)
• block
• choice
• iteration
Expression versus Statement
An expression is a unit of #declarative programming.
A statement is a unit of #imperative programming.
An expression is evaluated whereas a statement is executed.
Expressions
A combination of values, variables and functions that return a value and have no side effects.
Expressions can contain functions and functions may have side effects. A side effect is a change to the abstract state of the running program that does not depend on the function input.
Functional programs do not have assignment statements therefore the value of a variable never changes once defined. An expression is said to be referentially transparent if it can be replaced with its corresponding value without changing the program's behavior. Evaluating a referentially transparent function gives the same value for same arguments. Such functions are called pure functions. Referentially transparent expressions allow #memoization.
Statements
Do not return results and are executed solely for their side effects.
Simple statements:
• assertion
• assignment
• goto
• return
• call
Compound statements: (may contain statements as components)
• block
• choice
• iteration