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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 dont 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 havent 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 ", a, b_name); 
 }
 else {
 stdout.printf("%s not Found in %s ", 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(" ");
 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 ", 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 ", a_name, match);
 }
 else if (indexes.length == 1) {
 stdout.printf("Indexing %s: %s found at position %d ", 
 a_name, match, indexes[0]); 
 }
 else if (indexes.length == 2) {
 stdout.printf("Indexing %s: %s found at positions %d and %d ", 
 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. ", 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 ", orange.length);

 // Item from an array
 stdout.printf("Orange item #2: %s ", 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 ");
 return;
 }

Compile with a simple valac string_array.vala

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