This preview shows page 1-2-3-4-5-6-7-51-52-53-54-55-56-57-58-102-103-104-105-106-107-108 out of 108 pages.
61A Lecture 30Wednesday, November 9Wednesday, November 9, 2011Functional Programming2Wednesday, November 9, 2011Functional ProgrammingAll functions are pure functions2Wednesday, November 9, 2011Functional ProgrammingAll functions are pure functionsNo assignment and no mutable data types2Wednesday, November 9, 2011Functional ProgrammingAll functions are pure functionsNo assignment and no mutable data typesName-value bindings are permanent2Wednesday, November 9, 2011Functional ProgrammingAll functions are pure functionsNo assignment and no mutable data typesName-value bindings are permanentAdvantages of functional programming:2Wednesday, November 9, 2011Functional ProgrammingAll functions are pure functionsNo assignment and no mutable data typesName-value bindings are permanentAdvantages of functional programming:•The value of an expression is independent of the order in which sub-expressions are evaluated2Wednesday, November 9, 2011Functional ProgrammingAll functions are pure functionsNo assignment and no mutable data typesName-value bindings are permanentAdvantages of functional programming:•The value of an expression is independent of the order in which sub-expressions are evaluated•Sub-expressions can safely be evaluated in parallel or lazily2Wednesday, November 9, 2011Functional ProgrammingAll functions are pure functionsNo assignment and no mutable data typesName-value bindings are permanentAdvantages of functional programming:•The value of an expression is independent of the order in which sub-expressions are evaluated•Sub-expressions can safely be evaluated in parallel or lazily•Referential transparency: The value of an expression does not change when we substitute one of its subexpression with the value of that subexpression.2Wednesday, November 9, 2011Functional ProgrammingAll functions are pure functionsNo assignment and no mutable data typesName-value bindings are permanentAdvantages of functional programming:•The value of an expression is independent of the order in which sub-expressions are evaluated•Sub-expressions can safely be evaluated in parallel or lazily•Referential transparency: The value of an expression does not change when we substitute one of its subexpression with the value of that subexpression.The subset of Logo we have considered so far is functional(except for print/show)2Wednesday, November 9, 2011The Logo Assignment Procedure3Wednesday, November 9, 2011The Logo Assignment ProcedureLogo binds variable names to values, as in Python3Wednesday, November 9, 2011The Logo Assignment ProcedureLogo binds variable names to values, as in PythonAn environment stores name bindings in a sequence of frames3Wednesday, November 9, 2011The Logo Assignment ProcedureLogo binds variable names to values, as in PythonAn environment stores name bindings in a sequence of framesEach frame can have at most one value bound to a given name 3Wednesday, November 9, 2011The Logo Assignment ProcedureLogo binds variable names to values, as in PythonAn environment stores name bindings in a sequence of framesEach frame can have at most one value bound to a given name The make procedure adds or changes variable bindings3Wednesday, November 9, 2011The Logo Assignment ProcedureLogo binds variable names to values, as in PythonAn environment stores name bindings in a sequence of framesEach frame can have at most one value bound to a given name The make procedure adds or changes variable bindings3? make "x 2Wednesday, November 9, 2011The Logo Assignment ProcedureLogo binds variable names to values, as in PythonAn environment stores name bindings in a sequence of framesEach frame can have at most one value bound to a given name The make procedure adds or changes variable bindings3? make "x 2Values bound to names are looked up using variable expressionsWednesday, November 9, 2011The Logo Assignment ProcedureLogo binds variable names to values, as in PythonAn environment stores name bindings in a sequence of framesEach frame can have at most one value bound to a given name The make procedure adds or changes variable bindings3? make "x 2Values bound to names are looked up using variable expressions? print :x2Wednesday, November 9, 2011The Logo Assignment ProcedureLogo binds variable names to values, as in PythonAn environment stores name bindings in a sequence of framesEach frame can have at most one value bound to a given name The make procedure adds or changes variable bindings3? make "x 2Values bound to names are looked up using variable expressions? print :x2DemoWednesday, November 9, 2011Namespaces for Variables and Procedures4Wednesday, November 9, 2011Namespaces for Variables and Procedures4FRAMESWednesday, November 9, 2011Namespaces for Variables and Procedures4FRAMES PROCEDURESWednesday, November 9, 2011Namespaces for Variables and Procedures4x: 2FRAMES PROCEDURESWednesday, November 9, 2011Namespaces for Variables and Procedures4x: 2FRAMES PROCEDURESsum :x :y<built-in>first :x<built-in>sum:first:make :n :v<built-in>make:...Wednesday, November 9, 2011Namespaces for Variables and Procedures4x: 2FRAMES PROCEDURESsum :x :y<built-in>first :x<built-in>sum:first:make :n :v<built-in>make:...? make "sum 3Wednesday, November 9, 2011Namespaces for Variables and Procedures4x: 2FRAMES PROCEDURESsum :x :y<built-in>first :x<built-in>sum:first:make :n :v<built-in>make:...? make "sum 3sum: 3Wednesday, November 9, 2011Namespaces for Variables and Procedures4x: 2FRAMES PROCEDURESsum :x :y<built-in>first :x<built-in>sum:first:make :n :v<built-in>make:...? make "sum 3sum: 3DemoWednesday, November 9, 2011Assignment Rules5Wednesday, November 9, 2011Assignment RulesLogo assignment has different rules from Python assignment:5Wednesday, November 9, 2011Assignment RulesLogo assignment has different rules from Python assignment:5? make <name> <value>Wednesday, November 9, 2011Assignment RulesLogo assignment has different rules from Python assignment:5•If the name is already bound, make re-binds that name in the first frame in which the name is bound.? make <name> <value>Wednesday, November 9, 2011Assignment RulesLogo assignment has different rules from Python assignment:5•If the name is already bound, make re-binds that name in the first frame in which the name is bound.? make <name> <value>Like non-local Python assignmentWednesday, November 9, 2011Assignment RulesLogo assignment has different rules from Python assignment:5•If the name is already bound, make re-binds that name
View Full Document
Unlocking...