Flow Control

Control Logic Blocks

Fluency Programming Language follows the JavaScript / ECMAScript (ES6) syntax closely.

Conditional Logic

IF - ELSE - ELSEIF

An example FPL code block showing 'if' / 'elseif' / 'else' support:

function main() {
    let s = 100
    if (s == 5) {
        printf("s is equal to 5")
    } elseif (s < 10) {
        printf("s is less than 10 (and is not 5)")
    } else {
        printf("s is greater or equal to 10")
    }
    return {}
}

Note: The elseif keyword slightly differs from the ES6 standards of else if.

• Value to bool conversion:
  • false, null, undefined, 0, "", are evaluated false, while all other values are true

Loops

FOR Loop

An example FPL code block showing FOR loop support:

The standard three-component FOR loop: for init?; condition?; post? { }

function main() {
    let list = [0, 10, 20]
    for (let i = 0; i < len(list); i++) {
        printf("index: %d:  value: %d", i, list[i])
        if (i == 5) {
            printf("break")
            break // break out of the current for loop
        } else {
            continue // skip the current iteration of the for loop
        }
    }
    return {}
}

Alternative 'for-each' type loops:

for <index> <entry> = range <list> { }

for <key> <value> = range <map> { }

Note: The for ... range loop also supports utf8 encoded string. In this case, the index of the loop is the starting position of the current rune, as measured by bytes. See the example below:

function main() {
    let lst = [0, 10, 20]
    for i, v = range lst {
        printf("index: %d:  value: %d", i, v)
    }

    let map = {x:0, y:10, z:20}
    for k, v = range map {
        printf("key: %s:  value: %d", k, v)
    }

    // works for utf8 encoded strings
    let nihongo = "日本語"
    for i, s = range nihongo {
        printf("i:%d  s:%s", i, s)
    }
    // i:0  s:日
    // i:3  s:本
    // i:6  s:語
    return {}
}

Note: The range keyword in FOR loops are not part of the ES6 standards.

Break

Breaks out of the current FOR loop

function main() {
    ...
    if (i == 5) {
        printf("break")
        break // break out of the current for loop
    } else {
        continue // skip the current iteration of the for loop
    }
    ...
}

Continue

Skips the current iteration of the FOR loop

Try / Throw Error Logic

TRY - CATCH - FINALLY Logic

An example FPL code block showing try / catch / finally logic support:

function main() {
    try {
        nonExistentFunction();
    } catch (e) {
        printf("%s: %s", e.name, e.message);
        // print out: ReferenceError: nonExistentFunction is not defined
    } finally {
        // execute after the try block and catch block(s) execute,
        // but before the statements following the try...catch...finally block
    }
}

THROW Error

An error can be thrown with the throw keyword:

function main() {
    throw new Error("invalid data type")
}

Function 'Return'

Return

A function ends with a return statement, returning a <value> to the caller.

function main() {
    return <value>
}