Text Templates in Chapel

Chapel offers built-in support for creating dynamic content or showing customized output to the user with the IO module. We’ll use this module to demonstrate text template functionality similar to Go’s text/template package.

use IO;

proc main() {
    // We can create a simple template string with placeholders
    var t1 = "Value is %s\n";

    // By "executing" the template we generate its text with
    // specific values for its placeholders.
    writef(t1, "some text");
    writef(t1, 5);
    writef(t1, ["Chapel", "C++", "Rust", "Go"]);

    // Helper function we'll use below.
    proc create(name: string, t: string) {
        return t;
    }

    // If the data is a record we can use string interpolation
    // to access its fields. The fields should be visible to be
    // accessible when formatting.
    var t2 = create("t2", "Name: %s\n");

    record Person {
        var name: string;
    }
    var person = new Person("Jane Doe");
    writef(t2, person.name);

    // The same applies to associative arrays (similar to maps in Go)
    var personMap: [string] string;
    personMap["Name"] = "Mickey Mouse";
    writef(t2, personMap["Name"]);

    // Conditional execution can be achieved using if-else statements
    // in conjunction with string formatting
    var t3 = create("t3", "% if %s then yes else no\n");
    writef(t3, "not empty");
    writef(t3, "");

    // Loop through arrays using for loops and string formatting
    var t4 = create("t4", "Range: %s\n");
    var languages = ["Chapel", "C++", "Rust", "Go"];
    var rangeStr = " ".join(languages);
    writef(t4, rangeStr);
}

To run the program, save it as text_templates.chpl and use the Chapel compiler:

$ chpl text_templates.chpl -o text_templates
$ ./text_templates
Value is some text
Value is 5
Value is Chapel C++ Rust Go
Name: Jane Doe
Name: Mickey Mouse
yes
no
Range: Chapel C++ Rust Go

In this Chapel version:

We use the IO module for input/output operations.
String formatting is done using writef function, which is similar to C’s printf.
Chapel doesn’t have a built-in template system like Go, so we simulate it using string formatting.
Records in Chapel are similar to structs in Go.
Associative arrays in Chapel are used to demonstrate map-like behavior.
Conditional execution is simulated using if-else statements in conjunction with string formatting.
Looping through arrays is done using Chapel’s built-in iteration and joining capabilities.

While Chapel doesn’t have a direct equivalent to Go’s template package, this example demonstrates how to achieve similar text formatting and dynamic content generation using Chapel’s string manipulation and I/O capabilities.

String Formatting in Chapel

Regular Expressions in Chapel

Learn X By Example

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Text Templates in Chapel