Statements

Statements represent a basic mechanism of control flow in TML. TML is a structured imperative language, and supports familiar statement types.

Selection statements

If statement

If statement is used to redirect control flow based on the result of condition expression. Depending on whether the condition is true or false, main or else branch is chosen.

Condition expressions are evaluated top to bottom. Only one branch is executed, when the first true condition expression is encountered.

Serial checks can be specified concisely using elseif. else and elseif branches are optional. If all checks returned false, else branch is executed, if present.

Condition must be of bool type.

The most general form of the if statement:

if <condition>:
    <then-body>
elseif <condition>:
    <elseif-body>
else:
    <else-body>
end

Example:

if p.multiplication == "Matrix(K*u)":
    t.out = p.gain * t.in
elseif p.multiplication == "Const":
    t.out = t.in
else:
    t.out = 0
end

Iteration statements

For statement

For statement enables iterating over a range of values. Only ranges bounded on both start and end can be used in for statements.

For more details about range expressions, see Range Expressions.

    for i = 1:10:2:      # start, increment?, end (not included)
        #for body
        x = i
    end

    a = [1, 2, 3]

    for i = 0:a.len:
        #for body
        x = i
    end

Note

Current implementation allows only iterating over a range. Iterating over tensors will be implemented in the future.

While statement

While statement enables executing instructions in the body as long as the while condition is true. Condition expression is evaluated before every loop iteration.

Condition must be of bool type.

while <condition>:
    <body>
end

x = 1

while x < 5:
    y += 1
end

Return statement

return statement is used to end an execution of a callee function and return to the caller.

If function is void (i.e. has no return type), return statement is optional and is used only to prematurely terminate callee execution.

If function is non-void (i.e. has a return type such as a scalar or a tensor), return statement is mandatory and all paths must have a return statement. Typing rules for assignment are applied for return expressions (for more details, see Type system and Broadcasting).

fn test():
    x = 0

    if x == 1:
        return # Return is optional in void functions
    end

    y = 5
end

fn test() real:
    x = 0

    if x == 1:
        return 1
    end

    return 1.5
end

fn test() tensor<int, 5>:
    x = 0

    if x == 1:
        return 5 # Broadcasting is automatically applied
    end

    return [1, 1, 1, 1, 1]
end

Jump statement

TML is a structured language, and only jumps out of the loops are allowed. Supported jump statements are break and continue.

break - jump out of the closest loop
continue - jump to the next iteration of the closest loop

break and continue must be enclosed by a loop.

loc_out = 0

for idx = 1:10:
    if idx == 0:
        continue
    elseif idx == 5:
        break
    end

    loc_out += num
end