Held: Monday, 23 February 2015

Back to Outline 19 - Conditionals. On to Outline 21 - Naming Local Values.

Summary

We revisit procedures in Scheme. We consider a variety of techniques for writing anonymous procedures, procedures without names.

Related Pages

• Reading: Anonymous Procedures
• Lab: Anonymous Procedures
• Morning EBoard 20 (Source a.m. 20)
• Afternoon EBoard 20 (Source p.m. 20)

Overview

• What is a procedure?
• Describing procedures.
• Anonymous procedures.
• Anonymous procedures through lambda expressions.
• Other kinds of anonymous procedures.

Administrivia

• New partners!
• Review session tonight at 7pm.
• I hope you had a great weekend and a great two days without me. I think I've caught up on all of the email questions I've received. If not, let me know.
• Office hours today at 11:00 a.m. and 3:15 p.m. Office hours Tuesday at 10:00 a.m.
  
  • http://rebelsky.youcanbook.me
  • Remember that if you invoked "There's More To Life" on the exam, you need to meet with me.
• We'll debrief on the different models of conditionals and why you might use each of them.

Upcoming Work

• Homework 5.
  • Due Tuesday at 10:30 p.m.
  • Note that 6P-style documentation is expected for every primary procedure you write.
• Lab writeup for today: Exercise 5, parts b-f, http://bit.ly/151-2015S-lab20
• Reading for Tuesday
  • Local Bindings

Extra Credit Opportunities

Academic

• Pioneer Diversity Council Diversity Dialogue, 8:30 p.m. 26th, Main Quad "Academic Athletes and Academic Students". Note new date!

Peer Support (Morning Section)

• Julia's radio show, "The Hot Box". Wednesday night/Thursday morning 1:00-2:00 a.m.
• Host a prospie.

Peer Support (Afternoon Section)

• ???

Other Good Things

• ???

What is a procedure?

• One of the basic building blocks of programming.
• Essentially, an encapsulated algorithm
  • Takes some inputs
  • Generates some outputs

Describing Procedures

Traditionally, we write something like

(define *name-of-procedure*
  (lambda (*parameters*)
    *body*))

When applying a procedure, we effectively substitute the arguments we call the procedure on for the parameters in the body, and then evaluate the body.

Anonymous Procedures

• Procedures without names.
• Useful when we just need a procedure once
  • Saves the need to define it (code is more concise)
  • Saves the need to document it
  • Makes code work on its own
• In Scheme, whereever you write a procedure name, you can also write the corresponding lambda expression.
• Very useful with map
• Examples
• ((lambda (x y) (* (+ x y) (- x y))) 2 3)
• (map (lambda (x) (* 5 (+ 1 x))) (iota 10))

Other ways to build anonymous procedures

• Sectioning
• Composition

Lab

• Do the lab.
• Be prepared to reflect.