Expression language

Logic in TIFT is encoded using a javascipt-like expression language.

Hello world

print("hello world")

Outputs:

hello world

Arithmetic expressions

print(5 * (6 - 2))

Outputs:

Expression chaining

Multiple commands can be chained together using do

do(
    print("foo"),
    print("bar"),
    print("baz")
)

Outputs:

foo
bar
baz

Variable assignment

Variables can be assigned using the = assignement operator, set and def

assigment operator

do(
    a = 3,
    b = a + 7,
    print(a),
    print(b)
)

Outputs:

3
10

set

Set sets a variable to particular value.

do(
    set(a, 3),
    set(b, a + 7),
    print(a),
    print(b)
);

Outputs:

3
10

def

def always creates a new variable. Variables are scoped to a do block In this example variable a is shadowed by a new a in the nested do block, and the value does not overwrite the previous value of a

do(
    def(a,"foo"),
    def(b,"bar"),
    do(
        def(a,"baz"),
        print(a),
        print(b),
        set(b,"qux")
    ),
    print(a),
    print(b)
)

Outputs:

baz
bar
foo
qux

Arrays

Arrays are defined with square brackets.

do(
    obj.arr = ["foo", "bar"],
    obj.arr[0] = "baz",
    print(obj.arr[0]),
    print(obj.arr[1])
)

Outputs:

baz
bar

Enhanced assignment

Enhanced assignment operators are supported +=, -=, *=, /=

do(
    a = 2,
    b = 4,
    b *= a,
    a += 5 + 5,
    write(a),
    write(b)
)

Outputs:

12
8

If expressions

If expressions can be written with the following syntax if(expr).then(if_true).else(if_false)

if(3 > 2)
    .then(print("foo"))
    .else(print("bar"))

Outputs:

foo

ifs are expressions, so they return the result

do(
    myvar = if(3>2)
               .then("foo")
               .else("bar"),
    print(myvar)
)

Outputs:

foo

Switch expressions

Switch expression use the following syntax:

do(
    set(a, 3),
    set(b, switch(a)
            .case(1).then('one')
            .case(2).then('two')
            .default('three')),
    print(b)
)

Outputs:

three

Fall through

Case methods can be chained

do(
    set(a,1),
    set(b, switch(a)
                .case(1).case(2).then("one or two")
                .default('three')),
    print(b)
)

Outputs:

one or two

Object properties

Although objects can't be defined in the expression language, object properties (eg created in the yaml file) can be accessed using . notation.

do(
    player.score = 100,
    print(player.score)
)

Outputs:

Functions

Functions can be created using fn

do(
    def(add, fn([param1, param2], param1 + param2)),
    result = add(2,3),
    print(result)
)

Outputs

Closures

Functions can capture the local scope when the function is created (known as a closure)

do(
    def(createAdd, fn([param1], do(
        fn([param2], param1 + param2)
    ))),
    def(addSeven, createAdd(7)),
    result = addSeven(3),
    print(result)
)

Outputs: