Credits: My WPI colleague Glynis Hamel designed a set of Kiva-inspired exercises for her intro course. Shriram Krishnamurthi prototyped the teachpack so we could pull in actual Kiva data. I put the two together and added some exercises for my students.
© Kathi Fisler, Glynis Hamel, Shriram Krishnamurthi: 2007
Kiva.org connects individuals with microfinance opportunities in the developing world. Small business owners in developing countries request loans through Kiva. Kiva advertises these requests and lets individuals contribute small amounts to borrowers of their choice.
In these exercises, you will develop data definitions for key Kiva information and functions to process that information. You will also hook up your code to the Kiva website, so you can test your code on Kiva's actual data. This is a big part of what you'd need to do to write custom scripts or mashups based on Kiva's data.
The information about a borrower consists of their name, size of team, home country, type of business, requested amount, and percentage of the requested amount raised so far. Develop a data definition for a list of borrowers and an example using your data definition.
Write the template for functions over lists of borrowers.
Write a function funds-needed that consumes a list
of borrowers and produces the total amount of money that these
borrowers are still seeking (ie, the sum of the amounts requested but
not yet raised across all borrowers).
Write a function find-by-country that consumes a
country and a list of borrowers and returns the list of borrowers who
are from that country.
Download and install this kiva-teachpack. (Install it by going to the "Language" menu, selecting "Add teachpack", then "Install teachpack" on the dialog box. Once the teachpack name appears in the right-hand box, highlight it and click "OK").
[NOTE:We updated the teachpack in March 2008 to also extract data on the number of entrepreneurs involved in each Kiva group (this seems to be a new feature on their end in which groups of people request a collective loan). The former teachpack that assumed only single entrepreneurs (for backwards compatibility) is still available, at least for now.]
The teachpack lets you use your code on actual data from the Kiva
website. To use it, you first need a function to convert data from
the website to your structure. The teachpack provides a constant
sample-data that contains a snapshot of data taken from
the website. This data is a list of lists of strings and numbers, one
inner list per borrower. Using sample-data as a test
case, write a function convert to convert the list of
entries in the sample data to a list of your structures. The Scheme
functions second, third, etc (up to
ninth) can access items at those positions in a list
(similar to first).
Now you can hook up your code to the live Kiva data:
get-kiva-data/page which takes a page number (usually
numbers below 5) and extracts the data on the given page number on the kiva
web site into the same form as sample-data. The function
returns an empty list if the given page number doesn't exist (ie, is too high).
get-kiva-data that consumes no arguments and produces a
list of similar format to sample-data.
Both of these functions will omit entries whose html on the website was formatted differently from our expectations.
For more advanced students (uses intermediate language level).
Write a function search-borrowers that consumes a
list of borrowers and a function from borrower to boolean (ie, a
predicate on borrowers) and returns a list of all borrowers for
which the function returns true. Use your function to reproduce the
results of find-by-country.
Use functions you've already written to write
funds-by-criterion that consumes a list of borrowers and
a predicate on borrowers and produces the total amount that borrowers
who satsify the predicate are still seeking.
[More Challenging] Write a function sort-by-need
that consumes a list of borrowers and produces a summary of how much
funding is needed per country (over all countries represented in the
list), with the summary results sorted by decreasing need. Entries in
your summary should indicate both the country and the amount required.
Compose existing functions where you can to write this, without
worrying about the efficiency of your solution. You may use Scheme's
built-in quicksort function; use the helpdesk to find its
contract.