Download Programming Languages

Programming Languages
Meeting 9
October 28/29, 2014
More Lists
From last time, continuing with the formal
approach to functional programming
• Objects
– Atoms
– Lists of objects
– The symbol called bottom, signifying “undefined”
• Functions on the set of objects, the only
operation on objects
– Partial
– Entire
Atoms
• Forms of atoms
– sequence of characters, a string, an identifier
– sequence of digits, an integer [perhaps with sign]
– syntax of a real number
– T, meaning true
– F, meaning false
– ϕ, the symbol representing the empty list
Notation
• One line function specification with choices,
developed by John Backus
• Symbols
: apply the function to the argument
is defined as
−> if – then
; else
Functional Programming Language
Four components
1. Objects
2. Primitive functions
3. Functional forms
4. Function definition mechanism, for
secondary functions
Primitives
Our set of primitives:
• first
• last
• head
• tail
• atom?
• nil?
• list?
For next time
1. Using the primitives and functionals, define
concat, a function that concatenates two lists.
2. Using the primitives and functionals, define
reverse, a function that produces a list in the
reverse order from its argument
3. Install LispWorks 6.1.1 Personal Edition from
lispworks.org
4. Explore LispWorks and define our primitives in
this system.