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A closer look to values and variables#

Handling values and variables is key to grasp any language. The flows shown in this page exemplify how this works in Agama. They should feel pretty natural to any programmer.

Note: As in most languages, code may contain comments. Use // to start a comment. Comments in Agama only span one line.

Literals#

Flow com.acme.basic.literals contains examples of literal values in Agama. Visit Literals in the language reference for a deeper insight.

Flow com.acme.basic.literals
    Basepath ""

b = true            // A boolean value
str = "Oh, Agama!"  // A string

integer = -10       // A signed number
real = 3.1416       // A number with decimal digits

surprise = null     // Interfacing with foreign languages makes null a need...

l = [ false, "Aga", 2.7183, null ]    // Lists are not "typed"

car = { brand: "Ford", color: null, model: 1963, overhaulsIn: [ 1979, 1999 ] }  // This is a map  

RRF "car_details.ftlh" car

Finish true

Template car_details.ftlh displays some data passed in variable car. Here is how it looks like:

<!doctype html>
<html xmlns="http://www.w3.org/1999/xhtml">
<body>
    <h1>My Car</h1>
    <dl>
        <dt>Brand</dt>
        <dd>${brand}</dd>

        <dt>Model</dt>
        <dd>${model?c}</dd>

        <dt>Overhauls:</dt>
        <dd>
            <#list overhaulsIn>
                <ul>
                    <#items as year>
                        <li>${year?c}</li>
                    </#items>
                </ul>
            <#else>
                None yet
            </#list>
        </dd>        
    </dl>
    <form method="post" enctype="application/x-www-form-urlencoded">
        <input type="submit" value="Finish">
    </form>
</body>
</html>

Here, brand and model from car variable are shown. The overhaulsIn list is traversed using Freemarker's list directive to generate an HTML bulleted list. Usage of ?c avoids formatting numbers using locale settings. Without it, 1963 would be printed as 1,963. More on c here.

Variables#

Flow com.acme.basic.variables contains examples of variables manipulation in Agama. In the language reference visit Accessing and mutating data in variables and Advanced cases in variable manipulation for a deeper insight.

Flow com.acme.basic.variables
    Basepath ""

s = "Agama"           // A string
len = s.length        // String length (equals to 5)

letter = s[0]         // A string (equals to "A")
len = letter.length   // String length (equals to 1)

s[1] = "N"            // Strings are immutable. s is still "Agama"

l = [ true, false , null ]  // A list
len = l.length              // List length (equals to 3)
b = l[0]                    // A boolean (equals to true)

l[1] = true          // Replaces the former false value
nothing = l[4]       // This does not crash (equals to null)
l[3] = false         // Expands the list. It is now [ true, true, null, false]

car = { }            // Empty map
car.brand = "Ford"   // Attaches a new key/value pair
owner = car.owner    // Unknown key access (equals to null)

car.brand = "Simca"  // Overwrite the brand value
car.model = 1934     // car is now { brand: "Simca", model: 1934 }

key = "brand"  
s = car.$key         // Map access using dynamic key name (evaluates "Simca")
s = car."brand"      // Evaluates "Simca"

car.size = { H: 1.4, W: 1.2, L: 2.3 }
//car is now { brand: "Simca", model: 1934, size: { H: 1.4, W: 1.2, L: 2.3 } }
car.overhaulsIn = [ ]
height = car.size.H     // evaluates 1.4

RRF "car_details.ftlh" car

it = { success: true }
Finish it

As in the former example, brand and model from car are shown. Here, "None yet" will be displayed in the "Overhauls" section.

Note this flow terminates a bit differently compared to others; it supplies a map variable. So far all examples have used the "shortcut" notation for Finish. Here an "expanded" form is employed. This is often used when extra information needs to be passed in the Finish statement, however in this case, it has the same effect of doing Finish true.

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