Parsing

This is a pair exercise and must be competed in your tutorial or lab with your partner.

Download extract.h, or copy it into your current directory on a CSE system by running

$ cp /web/cs1511/17s2/week07/files/extract.h .

Download extract.c, or copy it into your current directory on a CSE system by running

$ cp /web/cs1511/17s2/week07/files/extract.c .

In this activity, you will be writing a series of C functions to convert a string to an integer, convert a string to a double, and to extract the x, y, z values from a string of the form “http://almondbread.cse.unsw.edu.au/mandelbrot/2/z/x/y/tile.bmp”.

For example, for the mandelbrot tile centered on (-1.0, -0.2) with a zoom level of 9, the string would be of the form: “http://almondbread.cse.unsw.edu.au/mandelbrot/2/9/-1.0/-0.2/tile.bmp”,

The prototypes for these functions are in a file called extract.h. Implement these functions in a file called extract.c.

You have been given a stub version of extract.c, with a simple main function already implemented. You have not been provided with stub functions; your task is to implement functions for the prototypes specified in extract.h:

triordinate extract (char *message);
extract takes a string, and extracts the x, y, and z parts into the triordinate structure, defined in extract.h.
long myAtoL (char *message);
myAtoL takes a string, extracts a signed long int in base 10 from it, and returns that value.
double myAtoD (char *message);
myAtoD takes a string, extracts a double in base 10 from it, and returns that value.

When working on myAtoL and myAtoD, think about the various boundary cases that a number might have. Zeros and signs are some examples… what are some others?

Warning! You may be tempted to use a library function like sscanf, atod, atoi, atol, strtol, or strtod, to read values. For now, don’t! Don’t use library functions unless you understand them, and for our purposes, that means you should be able to implement it. Try to build functions that actually parse values out of the string.

Your extract.c should #include extract.h and unit test your functions. We won’t test your main, just the three functions from the .h file.

To run Styl-o-matic:

$ 1511 stylomatic extract.c
Looks good!

You’ll get advice if you need to make changes to your code.

Submit your work with the give command, like so:

$ give cs1511 wk07_parsing

Or, if you are working from home, upload the relevant file(s) to the wk07_parsing activity on Give Online.