Objectives: Become familiar with designing a solution that requires a series of condition checks.

Learn how to translate such a design into code using the if$/$else if statements in $C++.$

One of the common uses of the if$/$else if statement is to determine the range in which a given

input value falls. $($This problem falls into the category of "point location" problems; this is a

one$-$dimensional point location problem$).$ In this exercise, we convert a floating point input that

specifies a wavelength in nanometers, into the appropriate color of the visible spectrum. The input

to the program is a real value that lies between $400\mathrm{.}0$ and $700\mathrm{.}0.$ The color conversions are:

$400$ Violet $<mn\; id="EditorElement\_12904155">4</mn><mn\; id="EditorElement\_12904156">4</mn><mn\; id="EditorElement\_12904157">5</mn>$;$445$ Indigo $<mn\; id="EditorElement\_12904118">4</mn><mn\; id="EditorElement\_12904119">7</mn><mn\; id="EditorElement\_12904120">5</mn>$;$475$ Blue $<mn\; id="EditorElement\_12904083">5</mn><mn\; id="EditorElement\_12904084">1</mn><mn\; id="EditorElement\_12904085">0</mn>$;$510$ Green $<mn\; id="EditorElement\_12904047">5</mn><mn\; id="EditorElement\_12904048">7</mn><mn\; id="EditorElement\_12904049">0</mn>$;$570$ Yellow $$

$590$;$590$ Orange $<mn\; id="EditorElement\_12903966">6</mn><mn\; id="EditorElement\_12903967">5</mn><mn\; id="EditorElement\_12903968">0</mn>$;$650$ Red

Assumption: We shall assume for now that the input always falls within this range $($the user of

the program must take on the responsibility of ensuring that the input is correct, and if the input

is outside the range, the program is not expected to give correct answers; see the second sample

execution$).$

The entire range of input values can be represented by the following structure:

$400$dots$445$dots$475$dots$510$dots$570$dots$590$dots$650$dots$700$

The lowest possible input value is $400\mathrm{.}0$ and the highest possible value is $700\mathrm{.}0$ Each of the in$-$

between numbers $($such as $445,475)$ serves as a "divider"; put together, they partition the entire

range into $7$ sub$-$ranges.

We can write a conditional statement to achieve this partition. Note that at each step we are

comparing the input with one of the "dividers", thus narrowing the range within we much we must

continue the search.

Strategy. Our strategy is as follows: Compare the input number with the first divider$(445).$ If

the number is smaller than the divider, we print the answer "Violet"; if not we continue with the

next divider.

Sample execution$($good input$)$:

Please input a wavelength between $400\mathrm{.}0$ and $700\mathrm{.}0$: $475\mathrm{.}0$

Your wavelength corresponds to the color Blue

Thank$-$you for using our program!