String Arrays in Vala

String Arrays are simply bunches of strings grouped together

string[] apples = {"red delicious", "granny smith", "macintosh", "gala", "fuji"}

They look like Python lists, but they are not. They often don't work like lists (you cannot slice them), but they work *really* fast. They are useful if you have a data set that is (mostly) immutable...you can append to it, but I haven't found a way to delete strings from the array without copying everything else into a new array.

Here is a demo program showing how to

• Create a string array
• Append a string to an array
• Match a string in an array
• Determine the index of the matched string
• Retrieve a string from the array (non-destructively)
• Replace a string with another withing an array
• Concatenate the array into a single string (for printing)

// string_array.vala

// If a in b
void if_a_in_b ( string a, string[] b, string b_name )  {
    if (a in b) { 
        stdout.printf("Found %s in %s\n", a, b_name); 
    }
    else {
        stdout.printf("%s not Found in %s\n", a, b_name);
    }
    return;
}


// One way to print an array
void print1 (string[] a, string a_name) {
    stdout.printf("Array %s: ", a_name);
    foreach (string item in a) {
        stdout.printf("%s, ", item);
    }
    stdout.printf("\n");
    return;
}

// Another way to print an array
void print2 (string[] a, string a_name) {
    string a_string = string.joinv(", ", a);
    stdout.printf("Array %s : %s\n", a_name, a_string);
    return;
}

// Index of an item in an array
void index_array (string[] a, string a_name, string match) {
    // Record the index of all matches
    int[] indexes = {};
    int i;
    for (i = 0; i < a.length; i++) {
        if (a[i] == match) {
            indexes += i;
        }
    }
    // Print the results
    if (indexes.length == 0) {
        stdout.printf("Indexing %s: %s not found\n", a_name, match);
    }
    else if (indexes.length == 1) {
        stdout.printf("Indexing %s: %s found at position %d\n", 
        a_name, match, indexes[0]);        
    }
    else if (indexes.length == 2) {
        stdout.printf("Indexing %s: %s found at positions %d and %d\n", 
        a_name, match, indexes[0], indexes[1]);        
    }
    else {
        stdout.printf("Indexing %s: %s found at positions ", 
        a_name, match);
        // Convert ints to a strings
        int j;
        for (j = 0; j < indexes.length; j++) {
            if ( j < (indexes.length - 1)) {
                stdout.printf("%d, ", indexes[j]);
            }
            else {
                stdout.printf("and %d.\n", indexes[j]);
            }
        }
    }
    return;
}



void arrays () {
    // Create two string arrays 
    string[] orange = { "fred", "joe", "allen", "steve" };
    string[] blue   = { "jane", "sam", "ellie", "terri" };

    // Test contents of each array
    if_a_in_b ("fred", orange, "Orange");
    if_a_in_b ("fred", blue, "Blue");

    // Length of an array
    stdout.printf("List length: %i\n", orange.length);

    // Item from an array
    stdout.printf("Orange item #2: %s\n", orange[1]);

    // Replace one string in an array
    blue[2] = "pamela";

    // Determine the index (location) of a string in an array
    index_array(blue, "blue", "pamela");

    // Append one string to an array 
    blue += "stacy";

    // Print an array
    print1(orange, "orange");
    print2(blue, "blue");

    return;
}


// Main
public static void main() {
    arrays ();
    stdout.printf("Hello, World\n");
    return;
    }

Compile with a simple valac string_array.vala

Web Scraper for string prices

I successfully tested a web scraper in python. It scrapes about 20 web pages for the prices of violin strings, then puts the prices in an OpenOffice document for handy printing. It is structured so I can add other output formats, and I could add an XML file to track prices over time or just print changes.

I'm installing it on the store iMac, and setting it as a daily recurring job. The finished file just pops onto the desktop, marked with the date.

A future version may compare prices from multiple sites.

The script and template live in the standard location for user scripts, /Users/username/Library/Scripts/scriptname/