Literals and Identifiers
Number literals
FunC allows decimal and hexadecimal integer literals (leading zeros are allowed).
For example, 0
, 123
, -17
, 00987
, 0xef
, 0xEF
, 0x0
, -0xfFAb
, 0x0001
, -0
, -0x0
are valid number literals.
String literals
Strings in FunC are quoted in double quotes "
like "this is a string"
. Special symbols like \n
and multi-line strings are not supported.
Optionally, string literals may specify a type after them, such as "string"u
.
The following string types are supported:
- without type—used for asm function definitions and to define a slice const by ASCII string
s
—defines a raw slice const by its contents (hex-encoded and optionally bit-padded)a
—creates a slice const containingMsgAddressInt
structure from a specified addressu
—creates an int const that corresponds to the hex values of the provided ASCII stringh
—creates an int const that is the first 32 bits of the SHA256 hash of the stringH
—creates an int const that is all 256 bits of the SHA256 hash of the stringc
—creates an int const that is crc32 value of the string
For example, the following values result in the corresponding consts:
"string"
becomesx{737472696e67}
slice const"abcdef"s
becomesx{abcdef}
slice const"Ef8zMzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMzMzM0vF"a
becomesx{9FE6666666666666666666666666666666666666666666666666666666666666667_}
slice const (addr_std$10 anycast:none$0 workchain_id:int8=0xFF address:bits256=0x33...33
)"NstK"u
becomes0x4e73744b
int const"transfer(slice, int)"h
becomes0x7a62e8a8
int const"transfer(slice, int)"H
becomes0x7a62e8a8ebac41bd6de16c65e7be363bc2d2cbc6a0873778dead4795c13db979
int const"transfer(slice, int)"c
becomes2235694568
int const
Identifiers
FunC allows a really wide class of identifiers (functions and variable names). Namely, any (single-line) string which doesn't contain special symbols ;
, ,
, (
, )
,
(space or tab), ~
and .
, doesn't start as a comment or string literal (with "
), isn't a number literal, isn't an underscore _
and isn't a keyword is a valid identifier (with the only exception that if it starts with `
, it must end with the same `
and can't contain any other `
except for these two).
Also, function names in function definitions may start with .
or ~
.
For example, those are valid identifiers:
query
,query'
,query''
elem0
,elem1
,elem2
CHECK
_internal_value
message_found?
get_pubkeys&signatures
dict::udict_set_builder
_+_
(the standard addition operator of type(int, int) -> int
in prefix notation, although it is already defined)fatal!
'
at the end of the name of a variable is conventionally used when some modified version of the old value is introduced. For example, almost all modifying built-in primitives for hashmap manipulation (except ones with the prefix ~
) take a hashmap and return a new version of the hashmap along with some other data, if necessary. It is convenient to name those values with the same name suffixed by '
.
Suffix ?
is usually used for boolean variables (TVM doesn't have a built-in type bool; bools are represented by integers: 0 is false and -1 is true) or for functions that return some flag, usually indicating success of the operation (like udict_get?
from stdlib.fc).
These are invalid identifiers:
take(first)Entry
"not_a_string
msg.sender
send_message,then_terminate
_
Some more uncommon examples of valid identifiers:
123valid
2+2=2*2
-valid
0xdead
{valid}
pa{--}in"`aaa`"
These are also invalid identifiers:
pa;;in"`aaa`"
(because;
is prohibited){-aaa-}
aa(bb
123
(it's a number)
Also, FunC has a special type of identifiers which is quoted in back quotes `
.
In the quotes, any symbols are allowed except for \n
and the quotes themselves.
For example, `I'm a variable too`
is a valid identifier, as well as `any symbols ; ~ () are allowed here...`
Constants
FunC allows to define compile-time constants that are substituted and precalculated during compilation.
Constants are defined as const optional-type identifier = value-or-expression;
optional-type
can be used to force a specific type of constant and for better readability.
As of now, int
and slice
types are supported.
value-or-expression
can be a literal or a pre-computable expression of literals and constants.
For example, constants can be defined as follows:
const int101 = 101;
definesint101
constant that is equivalent to the numeric literal101
const str1 = "const1", str2 = "aabbcc"s;
defines two constants that are equal to their corresponding stringsconst int int240 = ((int1 + int2) * 10) << 3;
definesint240
constant that equals the result of calculationconst slice str2r = str2;
definesstr2r
constant that is equal to the value ofstr2
constant
Since numeric constants are substituted during compilation, all optimization and pre-computations performed during the compilation are successfully performed (unlike the old method of defining constants via inline asm PUSHINT
s).