Slicing and dicing a list
There are many times when we want to pick items from a list. One of the most common kinds of processing is to treat the first item of a list as a special case. This leads to a kind of head-tail processing where we treat the head of a list differently from the items in the tail of a list.
We can use these techniques to make a copy of a list, also.
Getting ready
We have a spreadsheet that was used to record fuel consumption on a large sailboat. It has rows which look like this:
|
date |
engine on |
fuel height |
|
engine off | ||
|
Other notes | ||
|
10/25/2013 |
08:24 |
29 |
|
13:15 |
27 | |
|
calm seas—anchor solomon's island | ||
|
10/26/2013 |
09:12 |
27 |
|
18:25 |
22 | |
|
choppy—anchor in jackson's creek |
Fuel height? Yes. There's no float sensor to estimate the level of fuel in the tanks. Instead there's a sight-gauge that allows direct observation of the fuel. It's calibrated in inches of depth. For all practical purposes the tank is rectangular, so the depth shown can be converted to...
