Built-ins

This section describes some language constructions which are less fundamental than the ones described in previous articles. They could be defined in stdlib.fc but it would leave less room for the FunC optimizer.

Throwing exceptions

Exceptions can be thrown by conditional primitives throw_if, and throw_unless, and by unconditional throw. The first argument is the error code; the second is the condition (throw has only one argument). These primitives have parametrized versions throw_arg_if, throw_arg_unless, and throw_arg. The first argument is the exception parameter of any type; the second is the error code; the third is the condition (throw_arg has only two arguments).

Booleans

• true is alias for -1
• false is alias for 0

Dump variable

A variable can be dumped to the debug log by the ~dump function.

Dump string

A string can be dumped to the debug log by the ~strdump function.

Integer operations

• muldiv is a multiple-then-divide operation. The intermediate result is stored in 513-bit integer, so it won't overflow if the actual result fits into a 257-bit integer.

Other primitives

• null? checks whether the argument is null. By the value null of a TVM type, Null FunC represents absence of a value of some atomic type; see null values.
• touch and ~touch move a variable to the top of the stack
• at gets the value of a tuple component on the specified position