Assignment 2 - Functions & Conditionals

Instructions

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Read DCIC section §3.3 & §3.4 https://dcic-world.org/. The main ideas are:

• conditions & booleans
• repeated expressions to functions
• docstrings, testing and the design contract

So far, we’ve encountered values, such as a particular images, numbers or strings; and expressions, which are combinations of operations and values that evaluate to single values.

For all of the problems in this assignment (and for most of the rest of the assignments), your task will be to write one or more functions, programming constructs that allows you to reuse expressions with different inputs (called parameters) to solve particular problems.

Problems

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Warmup

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1. Create a Pyret file called flags2.arr. Write a function called vietnam-custom that takes two parameters first-color and second-color, and evaluates to the Vietnam flag if those parameters are “red” and “yellow”, or to an identically structured flag with different colors otherwise.

   Add a second function chile-custom that does the same thing for the Chilean flag. (You do not need to include doc-strings or where blocks for these functions.)

   Optional: include your favorite custom-color redesign of one of these flags.

Functions with doc-strings and where blocks

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For the remainder of these problems, include a doc-string explaining briefly what the function does, and 2-6 examples in a where block.

2. Create a Pyret file called weightlifting.arr. Write a function called bar-weight that takes arguments num-plates, and evaluates to the weight in pounds of a 20kg bar with num-plates number of 20kg plates. Use an approximate conversion such that one kg is 2.2 pounds, and check that an empty bar weighs 44 pounds, and a bar with two plates weighs 132 pounds.

3. In weightlifting.arr, add a function called bar-weight-custom that takes arguments bar of “w” or “m” for a women’s 15kg or a men’s 20kg bar respectively, and num-plates number of 20kg plates, and evaluates to the number of pounds the bar weighs.

4. Create a Pyret file called cookies.arr. Write a function called is-cookie-good that takes arguments flour, sugar, butter, and nuts (all measured in cups) and evaluates to a boolean of whether a cookie made using that amount (in cups) of ingredients is good.

   How can you tell whether a cookie is good? For starters, there should be more flour than sugar and butter combined (or it will fall apart). Next, consider the ratios of nuts to butter (“crunchiness”), sugar to flour (“sweetness”), and butter to sugar (“savoriness”). To be good, a cookie requires sweetness of at least 1/3, savoriness at least 2, and crunchiness at least 1/2.

   To test your function, make sure a cookie in the 3:2:1 ratio (3 cups flour, 2 cups butter, 1 cup sugar) with 1 cup of nuts is good. Make sure that a common cake recipe with 2 cups of flour, butter and sugar each (with no nuts) is not a good cookie.

Turn in

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Download your files flags2.arr, weightlifting.arr and cookies.arr files and email them to me.