teaching machines

CS 145 Lecture 18 – Bifurcations and N-way Choices

October 14, 2015 by Chris Johnson. Filed under cs145, fall 2015, lectures.

Agenda

• what ?s
• more bifurcations
• n-way choices
• restaurand

TODO

• Complete some problems from the Logic-1 section of Coding Bat. Write down the names of the problems you solve (and any other interesting tidbits of your thought) on a 1/4 sheet for Friday.

Note

Last time we introduced the bifurcation pattern, where we choose between two mutually exclusive paths through our code. Let’s continue to examine it through a series of examples:

• a zigzag pattern in Madeup
• a sunshine pattern in Madeup
• a method that computes the minimum of two numbers
• a method that computes the overall price of an item, including tax if necessary
• a method that determines if a String’s last character is !
• a method that given a month and day, tells what weekday that day is in the current year

We also extend this idea to making n-way choices. We’ll see that there’s nothing in Java’s if beyond bifurcations, but we can nest them such that it appears as though we were choosing between n alternatives.

Code

Bifur.java

/usr/lib/ruby/2.7.0/rubygems/dependency.rb:311:in `to_specs': Could not find 'coderay' (>= 0) among 56 total gem(s) (Gem::MissingSpecError)
Checked in 'GEM_PATH=/.gem/ruby/2.7.0:/var/lib/gems/2.7.0:/usr/lib/ruby/gems/2.7.0:/usr/share/rubygems-integration/2.7.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/2.7.0:/home/johnch/.gems', execute `gem env` for more information
	from /usr/lib/ruby/2.7.0/rubygems/dependency.rb:323:in `to_spec'
	from /usr/lib/ruby/2.7.0/rubygems/core_ext/kernel_gem.rb:62:in `gem'
	from ./coderay:24:in `
'

Restaurand.java

/usr/lib/ruby/2.7.0/rubygems/dependency.rb:311:in `to_specs': Could not find 'coderay' (>= 0) among 56 total gem(s) (Gem::MissingSpecError)
Checked in 'GEM_PATH=/.gem/ruby/2.7.0:/var/lib/gems/2.7.0:/usr/lib/ruby/gems/2.7.0:/usr/share/rubygems-integration/2.7.0:/usr/share/rubygems-integration/all:/usr/lib/x86_64-linux-gnu/rubygems-integration/2.7.0:/home/johnch/.gems', execute `gem env` for more information
	from /usr/lib/ruby/2.7.0/rubygems/dependency.rb:323:in `to_spec'
	from /usr/lib/ruby/2.7.0/rubygems/core_ext/kernel_gem.rb:62:in `gem'
	from ./coderay:24:in `
'

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