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FunC standard library

info

This section discusses the stdlib.fc library with standard functions used in FunC.

Currently, the library is just a wrapper for the most common assembler of the TVM commands which are not built-in. Each TVM command description used in the library can be found in the TVM documentation (appendix A). Some descriptions were borrowed for this document.

Some functions are commented out in the file. It means that they have already become built-ins for optimization purposes. However, the type signature and semantics remain the same.

Note that some less common commands are not presented in the stdlib. Someday they will also be added.

Tuple manipulation primitives​

The names and the types are mostly self-explaining. See polymorhism with forall for more info on the polymorphic functions.

Note that currently values of atomic type tuple cannot be cast into composite tuple types (e.g. [int, cell]) and vise versa.

Lisp-style lists​

Lists can be represented as nested 2-element tuples. Empty list is conventionally represented as TVM null value (it can be obtained by calling null()). For example, the tuple (1, (2, (3, null))) represents the list [1, 2, 3]. Elements of a list can be of different types.

cons​

forall X -> tuple cons(X head, tuple tail) asm "CONS";

Adds an element to the beginning of a lisp-style list.

uncons​

forall X -> (X, tuple) uncons(tuple list) asm "UNCONS";

Extracts the head and the tail of lisp-style list.

list_next​

forall X -> (tuple, X) list_next(tuple list) asm( -> 1 0) "UNCONS";

Extracts the head and tail of a lisp-style list. Can be used as a (non-)modifying method.

() foo(tuple xs) {
    int x = xs.list_next(); ;; get the first element
    int y = xs~list_next(); ;; pop the first element
    int z = xs~list_next(); ;; pop the second element
}

car​

forall X -> X car(tuple list) asm "CAR";

Returns the head of a lisp-style list.

cdr​

tuple cdr(tuple list) asm "CDR";

Returns the tail of a lisp-style list.

Other tuple primitives​

empty_tuple​

tuple empty_tuple() asm "NIL";

Creates 0-element tuple.

tpush​

forall X -> tuple tpush(tuple t, X value) asm "TPUSH";
forall X -> (tuple, ()) ~tpush(tuple t, X value) asm "TPUSH";

Appends the value x to the Tuple t = (x1, ..., xn) but only if the resulting Tuple t' = (x1, ..., xn, x) is no longer than 255 characters. Otherwise, a type check exception is thrown.

single​

forall X -> [X] single(X x) asm "SINGLE";

Creates a singletos, i.e., a tuple of length one.

unsingle​

forall X -> X unsingle([X] t) asm "UNSINGLE";

Unpacks a singletos.

pair​

forall X, Y -> [X, Y] pair(X x, Y y) asm "PAIR";

Creates a pair.

unpair​

forall X, Y -> (X, Y) unpair([X, Y] t) asm "UNPAIR";

Unpacks a pair.

triple​

forall X, Y, Z -> [X, Y, Z] triple(X x, Y y, Z z) asm "TRIPLE";

Creates a triple.

untriple​

forall X, Y, Z -> (X, Y, Z) untriple([X, Y, Z] t) asm "UNTRIPLE";

Unpacks a triple.

tuple4​

forall X, Y, Z, W -> [X, Y, Z, W] tuple4(X x, Y y, Z z, W w) asm "4 TUPLE";

Creates 4-element tuple.

untuple4​

forall X, Y, Z, W -> (X, Y, Z, W) untuple4([X, Y, Z, W] t) asm "4 UNTUPLE";

Unpacks 4-element tuple.

first​

forall X -> X first(tuple t) asm "FIRST";

Returns the first element of a tuple.

second​

forall X -> X second(tuple t) asm "SECOND";

Returns the second element of a tuple.

third​

forall X -> X third(tuple t) asm "THIRD";

Returns the third element of a tuple.

fourth​

forall X -> X fourth(tuple t) asm "3 INDEX";

Returns the fourth element of a tuple.

pair_first​

forall X, Y -> X pair_first([X, Y] p) asm "FIRST";

Returns the first element of a pair.

pair_second​

forall X, Y -> Y pair_second([X, Y] p) asm "SECOND";

Returns the second element of a pair.

triple_first​

forall X, Y, Z -> X triple_first([X, Y, Z] p) asm "FIRST";

Returns the first element of a triple.

triple_second​

forall X, Y, Z -> Y triple_second([X, Y, Z] p) asm "SECOND";

Returns the second element of a triple.

triple_third​

forall X, Y, Z -> Z triple_third([X, Y, Z] p) asm "THIRD";

Returns the third element of a triple.

Domain specific primitives​

Extracting info from c7​

Some useful information regarding smart contract invocation can be found in the c7 special register. These primitives serve for convenient data extraction.

now​

int now() asm "NOW";

Returns the current Unix time as an Integer

my_address​

slice my_address() asm "MYADDR";

Returns the internal address of the current smart contract as a Slice with MsgAddressInt. If necessary, it can be parsed further using primitives such as parse_std_addr.

get_balance​

[int, cell] get_balance() asm "BALANCE";

Returns the remaining balance of the smart contract as tuple consisting of int (the remaining balance in nanotoscoins) and cell (a dictionary with 32-bit keys representing the balance of “extra currencies”). Note that RAW primitives such as send_raw_message do not update this field.

cur_lt​

int cur_lt() asm "LTIME";

Returns the logical time of the current transaction.

block_lt​

int block_lt() asm "BLOCKLT";

Returns the starting logical time of the current block.

config_param​

cell config_param(int x) asm "CONFIGOPTPARAM";

Returns the value of the global configuration parameter with integer index i as cell or null value.

Hashes​

cell_hash​

int cell_hash(cell c) asm "HASHCU";

Computes the representation hash of cell c and returns it as a 256-bit unsigned integer x. Useful for signing and checking signatures of arbitrary entities represented by a tree of cells.

slice_hash​

int slice_hash(slice s) asm "HASHSU";

Computes the hash of slice s and returns it as a 256-bit unsigned integer x. The result is the same as if an ordinary cell containing only data and references from s had been created and its hash computed by cell_hash.

string_hash​

int string_hash(slice s) asm "SHA256U";

Computes sha256 of the data bits of slice s. If the bit length of s is not divisible by eight, it throws a cell underflow exception. The hash value is returned as a 256-bit unsigned integer x.

Signature checks​

check_signature​

int check_signature(int hash, slice signature, int public_key) asm "CHKSIGNU";

Checks the Ed25519 signature of hash (a 256-bit unsigned integer, usually computed as the hash of some data) using public_key (also represented by a 256-bit unsigned integer). The signature must contain at least 512 data bits; only the first 512 bits are used. If the signature is valid, the result is -1; otherwise, it is 0. Note that CHKSIGNU creates a 256-bit slice with the hash and calls CHKSIGNS. That is, if hash is computed as the hash of some data, this data is hashed twice, the second hashing occurring inside CHKSIGNS.

check_data_signature​

int check_data_signature(slice data, slice signature, int public_key) asm "CHKSIGNS";

Checks whether signature is a valid Ed25519 signature of the data portion of slice data using public_key, similarly to check_signature. If the bit length of data is not divisible by eight, it throws a cell underflow exception. The verification of Ed25519 signatures is a standard one, with sha256 used to reduce data to the 256-bit number that is actually signed.

Computation of boc size​

The primitives below may be useful for computing storage fees for user-provided data.

compute_data_size?​

(int, int, int, int) compute_data_size?(cell c, int max_cells) asm "CDATASIZEQ NULLSWAPIFNOT2 NULLSWAPIFNOT";

Returns (x, y, z, -1) or (null, null, null, 0). Recursively computes the count of distinct cells x, data bits y, and cell references z in the DAG rooted at cell c, effectively returning the total storage used by this DAG taking into account the identification of equal cells. The values of x, y, and z are computed by a depth-first traversal of this DAG with a hash table of visited cell hashes used to prevent visits of already-visited cells. The total count of visited cells x cannot exceed non-negative max_cells; otherwise, the computation is aborted before visiting the (max_cells + 1)-st cell and a zero flag is returned to indicate failure. If c is null, it returns x = y = z = 0.

slice_compute_data_size?​

(int, int, int, int) slice_compute_data_size?(slice s, int max_cells) asm "SDATASIZEQ NULLSWAPIFNOT2 NULLSWAPIFNOT";

Similar to compute_data_size? but accepting slice s instead of cell. The returned value of x does not take into account the cell that contains the slice s itself; however, the data bits and the cell references of s are accounted for in y and z.

compute_data_size​

(int, int, int) compute_data_size(cell c, int max_cells) impure asm "CDATASIZE";

A non-quiet version of compute_data_size? that throws a cell overflow exception (8) on failure.

slice_compute_data_size​

(int, int, int) slice_compute_data_size(slice s, int max_cells) impure asm "SDATASIZE";

A non-quiet version of slice_compute_data_size? that throws a cell overflow exception (8) on failure.

Persistent storage save and load​

get_data​

cell get_data() asm "c4 PUSH";

Returns the persistent contract storage cell. It can be parsed or modified with slice and builder primitives later.

set_data​

() set_data(cell c) impure asm "c4 POP";

Sets cell c as persistent contract data. You can update the persistent contract storage with this primitive.

Continuation primitives​

get_c3​

cont get_c3() impure asm "c3 PUSH";

Usually c3 has a continuation initialized by the whole code of the contract. It is used for function calls. The primitive returns the current value of c3.

set_c3​

() set_c3(cont c) impure asm "c3 POP";

Updates the current value of c3. Usually, it is used for updating smart contract code in runtime. Note that after execution of this primitive, the current code (and the stack of recursive function calls) won't change, but any other function call will use a function from the new code.

bless​

cont bless(slice s) impure asm "BLESS";

Transforms slice s into a simple ordinary continuation c with c.code = s, and an empty stack, and savelist.

accept_message​

() accept_message() impure asm "ACCEPT";

Sets the current gas limit gl to its maximum allowed value gm and resets the gas credit gc to zero, decreasing the value of gr by gc in the process. In other words, the current smart contract agrees to buy some gas to finish the current transaction. This action is required to process external messages that carry no value (hence no gas).

For more details check accept_message effects

set_gas_limit​

() set_gas_limit(int limit) impure asm "SETGASLIMIT";

Sets the current gas limit gl to the minimum of limit and gm, and resets the gas credit gc to zero. At that point, if the amount of consumed gas (including the present instruction) exceeds the resulting value of gl, an (unhandled) out of gas exception is thrown before setting new gas limits. Notice that set_gas_limit with an argument limit ≥ 2^63 − 1 is equivalent to accept_message.

For more details check accept_message effects

commit​

() commit() impure asm "COMMIT";

Commits the current state of registers c4 (“persistent data”) and c5 (“actions”) so that the current execution is considered “successful” with the saved values even if an exception is thrown later.

buy_gas​

() buy_gas(int gram) impure asm "BUYGAS";

Computes the amount of gas that can be bought for gram nanotoscoins and sets gl accordingly in the same way as set_gas_limit.

Actions primitives​

raw_reserve​

() raw_reserve(int amount, int mode) impure asm "RAWRESERVE";

Creates an output action which would reserve exactly amount nanotoscoins (if mode = 0), at most amount nanotoscoins (if mode = 2), or all but amount nanotoscoins (if mode = 1 or mode = 3) from the remaining balance of the account. It is roughly equivalent to creating an outbound message carrying amount nanotoscoins (or b − amount nanotoscoins, where b is the remaining balance) to oneself, so that the subsequent output actions would not be able to spend more money than the remainder. Bit +2 in mode means that the external action does not fail if the specified amount cannot be reserved; instead, all the remaining balance is reserved. Bit +8 in mode means amount <- -amount before performing any further actions. Bit +4 in mode means that amount is increased by the original balance of the current account (before the compute phase), including all extra currencies before performing any other checks and actions. Currently, amount must be a non-negative integer, and mode must be in the range 0..15.

raw_reserve_extra​

() raw_reserve_extra(int amount, cell extra_amount, int mode) impure asm "RAWRESERVEX";

Similar to raw_reserve but also accepts a dictionary extra_amount (represented by cell or null) with extra currencies. In this way, currencies other than Toscoin can be reserved.

send_raw_message​

() send_raw_message(cell msg, int mode) impure asm "SENDRAWMSG";

Sends a raw message contained in msg, which should contain a correctly serialized object Message X, with the only exception that the source address is allowed to have a dummy value addr_none (to be automatically replaced with the current smart contract address), and ihr_fee, fwd_fee, created_lt and created_at fields can have arbitrary values (to be rewritten with correct values during the action phase of the current transaction). The integer parameter mode contains the flags.

There are currently 3 Modes and 3 Flags for messages. You can combine a single mode with several (maybe none) flags to get a required mode. Combination simply means getting sum of their values. A table with descriptions of Modes and Flags is given below.

ModeDescription
0Ordinary message
64Carry all the remaining value of the inbound message in addition to the value initially indicated in the new message
128Carry all the remaining balance of the current smart contract instead of the value originally indicated in the message
FlagDescription
+1Pay transfer fees separately from the message value
+2Ignore any errors arising while processing this message during the action phase
+32Current account must be destroyed if its resulting balance is zero (often used with Mode 128)

For example, if you want to send a regular message and pay transfer fees separately, use the Mode 0 and Flag +1 to get mode = 1. If you want to send the whole contract balance and destroy it immidiately, use the Mode 128 and Flag +32 to get mode = 160.

set_code​

() set_code(cell new_code) impure asm "SETCODE";

Creates an output action that would change this smart contract code to that given by cell new_code. Notice that this change will take effect only after the successful termination of the current run of the smart contract. (Cf. set_c3)

Random number generator primitives​

The pseudo-random number generator uses the random seed, an unsigned 256-bit Integer, and (sometimes) other data kept in c7. The initial value of the random seed before a smart contract is executed in TOS Blockchain is a hash of the smart contract address and the global block random seed. If there are several runs of the same smart contract inside a block, then all of these runs will have the same random seed. This can be fixed, for example, by running randomize_lt before using the pseudo-random number generator for the first time.

caution

Keep in mind that random numbers generated by the functions below can be predicted if you do not use additional tricks.

random​

int random() impure asm "RANDU256";

Generates a new pseudo-random unsigned 256-bit integer x. The algorithm is as follows: if r is the old value of the random seed considered a 32-byte array (by constructing the big-endian representation of an unsigned 256-bit integer), then its sha512(r) is computed; the first 32 bytes of this hash are stored as the new value r' of the random seed, and the remaining 32 bytes are returned as the next random value x.

rand​

int rand(int range) impure asm "RAND";

Generates a new pseudo-random integer z in the range 0..range−1 (or range..−1 if range < 0). More precisely, an unsigned random value x is generated as in random; then z := x * range / 2^256 is computed.

get_seed​

int get_seed() impure asm "RANDSEED";

Returns the current random seed as an unsigned 256-bit integer.

set_seed​

int set_seed(int seed) impure asm "SETRAND";

Sets a random seed to an unsigned 256-bit seed.

randomize​

() randomize(int x) impure asm "ADDRAND";

Mixes an unsigned 256-bit integer x into a random seed r by setting the random seed to sha256 of the concatenation of two 32-byte strings: the first with a big-endian representation of the old seed r, and the second with a big-endian representation of x.

randomize_lt​

() randomize_lt() impure asm "LTIME" "ADDRAND";

Equivalent to randomize(cur_lt());.

Address manipulation primitives​

The address manipulation primitives listed below serialize and deserialize values according to the following TL-B scheme.

addr_none$00 = MsgAddressExt;

addr_extern$01 len:(## 8) external_address:(bits len)
             = MsgAddressExt;
             
anycast_info$_ depth:(#<= 30) { depth >= 1 }
  rewrite_pfx:(bits depth) = Anycast;
  
addr_std$10 anycast:(Maybe Anycast)
  workchain_id:int8 address:bits256 = MsgAddressInt;
  
addr_var$11 anycast:(Maybe Anycast) addr_len:(## 9)
  workchain_id:int32 address:(bits addr_len) = MsgAddressInt;
_ _:MsgAddressInt = MsgAddress;
_ _:MsgAddressExt = MsgAddress;

int_msg_info$0 ihr_disabled:Bool bounce:Bool bounced:Bool
  src:MsgAddress dest:MsgAddressInt
  value:CurrencyCollection ihr_fee:Grams fwd_fee:Grams
  created_lt:uint64 created_at:uint32 = CommonMsgInfoRelaxed;
  
ext_out_msg_info$11 src:MsgAddress dest:MsgAddressExt
  created_lt:uint64 created_at:uint32 = CommonMsgInfoRelaxed;

A deserialized MsgAddress is represented by the tuple t as follows:

  • addr_none is represented by t = (0), i.e., a tuple containing exactly one integer that equals zero
  • addr_extern is represented by t = (1, s), where slice s contains the field external_address. In other words, t is a pair (a tuple consisting of two entries), containing an integer equal to one and slice s
  • addr_std is represented by t = (2, u, x, s), where u is either null (if anycast is absent) or a slice s' containing rewrite_pfx (if anycast is present). Next, integer x is the workchain_id, and slice s contains the address
  • addr_var is represented by t = (3, u, x, s), where u, x, and s have the same meaning as for addr_std

load_msg_addr​

(slice, slice) load_msg_addr(slice s) asm( -> 1 0) "LDMSGADDR";

Loads from slice s the only prefix that is a valid MsgAddress and returns both this prefix s' and the remainder s'' of s as slices.

parse_addr​

tuple parse_addr(slice s) asm "PARSEMSGADDR";

Decomposes slice s containing a valid MsgAddress into tuple t with separate fields of this MsgAddress. If s is not a valid MsgAddress, a cell deserialization exception is thrown.

parse_std_addr​

(int, int) parse_std_addr(slice s) asm "REWRITESTDADDR";

Parses slice s containing a valid MsgAddressInt (usually msg_addr_std), applies rewriting from the anycast (if present) to the same-length prefix of the address, and returns both the workchain and the 256-bit address as integers. If the address is not 256-bit or if s is not a valid serialization of MsgAddressInt, throws a cell deserialization exception.

parse_var_addr​

(int, slice) parse_var_addr(slice s) asm "REWRITEVARADDR";

A variant of parse_std_addr that returns the (rewritten) address as a slice s, even if it is not exactly 256 bit long (represented by msg_addr_var).

Debug primitives​

Currently, only one function is available.

dump_stack​

() dump_stack() impure asm "DUMPSTK";

Dumps the stack (at most the top 255 values) and shows the total stack depth.

Slice primitives​

It is said that a primitive loads some data if it returns the data and the remainder of the slice (so it can also be used as a modifying method).

It is said that a primitive preloads some data if it returns only the data (it can be used as a non-modifying method).

Unless otherwise stated, loading and preloading primitives read data from a prefix of the slice.

begin_parse​

slice begin_parse(cell c) asm "CTOS";

Converts cell into slice. Notice that c must be either an ordinary cell or an exotic cell (see TVM.pdf, 3.1.2) which is automatically loaded to yield an ordinary cell c'converted into slice afterwards.

end_parse​

() end_parse(slice s) impure asm "ENDS";

Checks if s is empty. If not, throws an exception.

load_ref​

(slice, cell) load_ref(slice s) asm( -> 1 0) "LDREF";

Loads the first reference from a slice.

preload_ref​

cell preload_ref(slice s) asm "PLDREF";

Preloads the first reference from a slice.

load_int​

;; (slice, int) ~load_int(slice s, int len) asm(s len -> 1 0) "LDIX";

Loads a signed len-bit integer from a slice.

load_uint​

;; (slice, int) ~load_uint(slice s, int len) asm( -> 1 0) "LDUX";

Loads an unsigned len-bit integer from a slice.

preload_int​

;; int preload_int(slice s, int len) asm "PLDIX";

Preloads a signed len-bit integer from a slice.

preload_uint​

;; int preload_uint(slice s, int len) asm "PLDUX";

Preloads an unsigned len-bit integer from a slice.

load_bits​

;; (slice, slice) load_bits(slice s, int len) asm(s len -> 1 0) "LDSLICEX";

Loads the first 0 ≤ len ≤ 1023 bits from slice s into a separate slice s''.

preload_bits​

;; slice preload_bits(slice s, int len) asm "PLDSLICEX";

Preloads the first 0 ≤ len ≤ 1023 bits from slice s into a separate slice s''.

load_coins​

(slice, int) load_coins(slice s) asm( -> 1 0) "LDGRAMS";

Loads serialized amount of Toscoins (any unsigned integer up to 2^120 - 1).

skip_bits​

slice skip_bits(slice s, int len) asm "SDSKIPFIRST";
(slice, ()) ~skip_bits(slice s, int len) asm "SDSKIPFIRST";

Returns all but the first 0 ≤ len ≤ 1023 bits of s.

first_bits​

slice first_bits(slice s, int len) asm "SDCUTFIRST";

Returns the first 0 ≤ len ≤ 1023 bits of s.

skip_last_bits​

slice skip_last_bits(slice s, int len) asm "SDSKIPLAST";
(slice, ()) ~skip_last_bits(slice s, int len) asm "SDSKIPLAST";

Returns all but the last 0 ≤ len ≤ 1023 bits of s.

slice_last​

slice slice_last(slice s, int len) asm "SDCUTLAST";

Returns the last 0 ≤ len ≤ 1023 bits of s.

load_dict​

(slice, cell) load_dict(slice s) asm( -> 1 0) "LDDICT";

Loads a dictionary D from slice s. May be applied to dictionaries or to values of arbitrary Maybe ^Y types (returns null if nothing constructor is used).

preload_dict​

cell preload_dict(slice s) asm "PLDDICT";

Preloads a dictionary D from slice s.

skip_dict​

slice skip_dict(slice s) asm "SKIPDICT";

Loads a dictionary as load_dict but returns only the remainder of the slice.

Slice size primitives​

slice_refs​

int slice_refs(slice s) asm "SREFS";

Returns the number of references in slice s.

slice_bits​

int slice_bits(slice s) asm "SBITS";

Returns the number of data bits in slice s.

slice_bits_refs​

(int, int) slice_bits_refs(slice s) asm "SBITREFS";

Returns both the number of data bits and the number of references in s.

slice_empty?​

int slice_empty?(slice s) asm "SEMPTY";

Checks whether slice s is empty (i.e., contains no bits of data and no cell references).

slice_data_empty?​

int slice_data_empty?(slice s) asm "SDEMPTY";

Checks whether slice s has no bits of data.

slice_refs_empty?​

int slice_refs_empty?(slice s) asm "SREMPTY";

Checks whether slice s has no references.

slice_depth​

int slice_depth(slice s) asm "SDEPTH";

Returns the depth of slice s. If s has no references, then returns 0; otherwise, the returned value is one plus the maximum of depths of cells referred to from s.

Builder primitives​

It is said that a primitive stores a value x into a builder b if it returns a modified version of the builder b' with the value x stored at the end of it. It can be used as a non-modifying method.

All of the primitives listed below verify whether there is enough space in the builderfirst, and then the range of the value being serialized.

begin_cell​

builder begin_cell() asm "NEWC";

Creates a new empty builder.

end_cell​

cell end_cell(builder b) asm "ENDC";

Converts builder into an ordinary cell.

store_ref​

builder store_ref(builder b, cell c) asm(c b) "STREF";

Stores a reference to cell c into builder b.

store_uint​

builder store_uint(builder b, int x, int len) asm(x b len) "STUX";

Stores an unsigned len-bit integer x into b for 0 ≤ len ≤ 256.

store_int​

builder store_int(builder b, int x, int len) asm(x b len) "STIX";

Stores a signed len-bit integer x into b for 0 ≤ len ≤ 257.

store_slice​

builder store_slice(builder b, slice s) asm "STSLICER";

Stores slice s into builder b.

store_grams​

builder store_grams(builder b, int x) asm "STGRAMS";

Stores (serializes) an integer x in the range 0..2^120 − 1 into builder b. The serialization of x consists of a 4-bit unsigned big-endian integer l, which is the smallest integer l ≥ 0, such that x < 2^8l, followed by an 8l-bit unsigned big-endian representation of x. If x does not belong to the supported range, a range check exception is thrown.

It is the most common way of storing Toscoins.

store_dict​

builder store_dict(builder b, cell c) asm(c b) "STDICT";

Stores dictionary D represented by cell c or null into builder b. In other words, stores 1-bit and a reference to c if c is not null and 0-bit otherwise.

store_maybe_ref​

builder store_maybe_ref(builder b, cell c) asm(c b) "STOPTREF";

Equivalent to store_dict.

Builder size primitives​

builder_refs​

int builder_refs(builder b) asm "BREFS";

Returns the number of cell references already stored in builder b.

builder_bits​

int builder_bits(builder b) asm "BBITS";

Returns the number of data bits already stored in builder b.

builder_depth​

int builder_depth(builder b) asm "BDEPTH";

Returns the depth of builder b. If no cell references are stored in b, then returns 0; otherwise, the returned value is one plus the maximum of depths of cells referred to from b.

Cell primitives​

cell_depth​

int cell_depth(cell c) asm "CDEPTH";

Returns the depth of cell c. If c has no references, then return 0; otherwise, the returned value is one plus the maximum of depths of cells referred to from c. If c is a null instead of a cell, it returns zero.

cell_null?​

int cell_null?(cell c) asm "ISNULL";

Checks whether c is a null. Usually a null-cell represents an empty dictionary. FunC also has polymorphic null? built-in. (See built-ins.)

Dictionaries primitives​

caution

The dictionary primitives below are low-level and do not check that the structure of the cell, they are applied to, matches the operation signature. Applying a dictionary operation to a "non-dictionary" or applying an operation corresponding to one key length/sign to a dictionary with a different kind of keys, for instance simultaneous writing to one dictionary key-values with 8bit-signed key and 7bit-unsigned key, is Undefined Behavior. Often in such cases an exception is thrown, but in rare cases the wrong value can be written / read. Developers are strongly encouraged to avoid such code.

As said in TVM.pdf:

Dictionaries admit two different representations as TVM stack values:

  • A slice s with a serialization of a TL-B value of type HashmapE(n, X). In other words, s consists either of one bit equal to zero (if the dictionary is empty) or of one bit equal to one and a reference to a cell containing the root of the binary tree, i.e., a serialized value of type Hashmap(n, X).
  • A “Maybe cell” c^?, i.e., a value that is either a cell (containing a serialized value of type Hashmap(n, X) as before) or a null (corresponding to an empty dictionary, cf. null values). When a “Maybe cell” c^? is used to represent a dictionary, we usually denote it by D.

Most of the dictionary primitives listed below accept and return dictionaries in the second form, which is more convenient for stack manipulation. However, serialized dictionaries inside larger TL-B objects use the first representation.

In FunC dictionaries are also represented by the cell type with the implicit assumption that it may be a null value. There are no separate types for dictionaries with different key lengths or value types (after all, it's FunC, not FunC++).

Taxonomy note​

A dictionary primitive may interpret the keys of the dictionary either as unsigned l-bit integers, as signed l-bit integers, or as l-bit slices. The primitives listed below differ by the prefix before the word dict in their names. i stands for signed integer keys, u stands for unsigned integer keys, and an empty prefix stands for slice keys.

For example, udict_set is a set-by-key function for dictionaries with unsigned integer keys; idict_set is the corresponding function for dictionaries with signed integer keys; dict_set is the function for dictionaries with slice keys.

An empty prefix is used in the titles.

Also, some of the primitives have their counterparts prefixed with ~. It makes it possible to use them as modifying methods.

Dictionary's values​

A value in a dictionary may be stored either directly as a subslice of an inner dictionary cell or as a reference to a separate cell. In the first case, it is not guaranteed that if the value fits into a cell, it fits into the dictionary (because a part of the inner cell may already be occupied by a part of the corresponding key). On the other hand, the second storing way is less gas-efficient. The second way is equivalent to storing in the first way a slice with empty data bits and exactly one reference to the value.

dict_set​

cell udict_set(cell dict, int key_len, int index, slice value) asm(value index dict key_len) "DICTUSET";
cell idict_set(cell dict, int key_len, int index, slice value) asm(value index dict key_len) "DICTISET";
cell dict_set(cell dict, int key_len, slice index, slice value) asm(value index dict key_len) "DICTSET";
(cell, ()) ~udict_set(cell dict, int key_len, int index, slice value) asm(value index dict key_len) "DICTUSET";
(cell, ()) ~idict_set(cell dict, int key_len, int index, slice value) asm(value index dict key_len) "DICTISET";
(cell, ()) ~dict_set(cell dict, int key_len, slice index, slice value) asm(value index dict key_len) "DICTSET";

Sets the value associated with key_len-bit key index in dictionary dict to value (a slice) and returns the resulting dictionary.

dict_set_ref​

cell idict_set_ref(cell dict, int key_len, int index, cell value) asm(value index dict key_len) "DICTISETREF";
cell udict_set_ref(cell dict, int key_len, int index, cell value) asm(value index dict key_len) "DICTUSETREF";
(cell, ()) ~idict_set_ref(cell dict, int key_len, int index, cell value) asm(value index dict key_len) "DICTISETREF";
(cell, ()) ~udict_set_ref(cell dict, int key_len, int index, cell value) asm(value index dict key_len) "DICTUSETREF";

Similar to dict_set but with the value set to a reference to cell value.

dict_get?​

(slice, int) idict_get?(cell dict, int key_len, int index) asm(index dict key_len) "DICTIGET" "NULLSWAPIFNOT";
(slice, int) udict_get?(cell dict, int key_len, int index) asm(index dict key_len) "DICTUGET" "NULLSWAPIFNOT";

Looks up key index in dictionary dict with key_len-bit keys. On success, returns the value found as a slice along with a -1 flag indicating success. If fails, it returns (null, 0).

dict_get_ref?​

(cell, int) idict_get_ref?(cell dict, int key_len, int index) asm(index dict key_len) "DICTIGETREF";
(cell, int) udict_get_ref?(cell dict, int key_len, int index) asm(index dict key_len) "DICTUGETREF";

Similar to dict_get? but returns the first reference of the found value.

dict_get_ref​

cell idict_get_ref(cell dict, int key_len, int index) asm(index dict key_len) "DICTIGETOPTREF";

A variant of dict_get_ref? that returns null instead of the value if the key index is absent from the dictionary dict.

dict_set_get_ref​

(cell, cell) idict_set_get_ref(cell dict, int key_len, int index, cell value) asm(value index dict key_len) "DICTISETGETOPTREF";
(cell, cell) udict_set_get_ref(cell dict, int key_len, int index, cell value) asm(value index dict key_len) "DICTUSETGETOPTREF";

Sets the value associated with index to value (if value is null, then the key is deleted instead) and returns the old value (or null if the value was absent).

dict_delete?​

(cell, int) idict_delete?(cell dict, int key_len, int index) asm(index dict key_len) "DICTIDEL";
(cell, int) udict_delete?(cell dict, int key_len, int index) asm(index dict key_len) "DICTUDEL";

Deletes key_len-bit key index from the dictionary dict. If the key is present, returns the modified dictionary dict' and the success flag −1. Otherwise, returns the original dictionary dict and 0.

dict_delete_get?​

(cell, slice, int) idict_delete_get?(cell dict, int key_len, int index) asm(index dict key_len) "DICTIDELGET" "NULLSWAPIFNOT";
(cell, slice, int) udict_delete_get?(cell dict, int key_len, int index) asm(index dict key_len) "DICTUDELGET" "NULLSWAPIFNOT";
(cell, (slice, int)) ~idict_delete_get?(cell dict, int key_len, int index) asm(index dict key_len) "DICTIDELGET" "NULLSWAPIFNOT";
(cell, (slice, int)) ~udict_delete_get?(cell dict, int key_len, int index) asm(index dict key_len) "DICTUDELGET" "NULLSWAPIFNOT";

Deletes key_len-bit key index from dictionary dict. If the key is present, returns the modified dictionary dict', the original value x associated with the key k (represented by a Slice), and the success flag −1. Otherwise, returns (dict, null, 0).

dict_add?​

(cell, int) udict_add?(cell dict, int key_len, int index, slice value) asm(value index dict key_len) "DICTUADD";
(cell, int) idict_add?(cell dict, int key_len, int index, slice value) asm(value index dict key_len) "DICTIADD";

An add counterpart of dict_set sets the value associated with key index in dictionary dict to value but only if it is not already present in D. Returns either modified version of the dictionary and -1 flag or (dict, 0).

dict_replace?​

(cell, int) udict_replace?(cell dict, int key_len, int index, slice value) asm(value index dict key_len) "DICTUREPLACE";
(cell, int) idict_replace?(cell dict, int key_len, int index, slice value) asm(value index dict key_len) "DICTIREPLACE";

A replace operation similar to dict_set but which sets the value of key index in dictionary dict to value only if the key was already present in dict. Returns either modified version of the dictionary and -1 flag or (dict, 0).

Builder counterparts​

The following primitives accept the new value as a builder instead of a slice, which often is more convenient if the value needs to be serialized from several components computed in the stack. The net effect is roughly equivalent to converting b into a slice and executing the corresponding primitive listed above.

dict_set_builder​

cell udict_set_builder(cell dict, int key_len, int index, builder value) asm(value index dict key_len) "DICTUSETB";
cell idict_set_builder(cell dict, int key_len, int index, builder value) asm(value index dict key_len) "DICTISETB";
cell dict_set_builder(cell dict, int key_len, slice index, builder value) asm(value index dict key_len) "DICTSETB";
(cell, ()) ~idict_set_builder(cell dict, int key_len, int index, builder value) asm(value index dict key_len) "DICTISETB";
(cell, ()) ~udict_set_builder(cell dict, int key_len, int index, builder value) asm(value index dict key_len) "DICTUSETB";
(cell, ()) ~dict_set_builder(cell dict, int key_len, slice index, builder value) asm(value index dict key_len) "DICTSETB";

Similar to dict_set but accepts a builder.

dict_add_builder?​

(cell, int) udict_add_builder?(cell dict, int key_len, int index, builder value) asm(value index dict key_len) "DICTUADDB";
(cell, int) idict_add_builder?(cell dict, int key_len, int index, builder value) asm(value index dict key_len) "DICTIADDB";

Similar to dict_add? but accepts a builder.

dict_replace_builder?​

(cell, int) udict_replace_builder?(cell dict, int key_len, int index, builder value) asm(value index dict key_len) "DICTUREPLACEB";
(cell, int) idict_replace_builder?(cell dict, int key_len, int index, builder value) asm(value index dict key_len) "DICTIREPLACEB";

Similar to dict_replace? but accepts a builder.

dict_delete_get_min​

(cell, int, slice, int) udict_delete_get_min(cell dict, int key_len) asm(-> 0 2 1 3) "DICTUREMMIN" "NULLSWAPIFNOT2";
(cell, int, slice, int) idict_delete_get_min(cell dict, int key_len) asm(-> 0 2 1 3) "DICTIREMMIN" "NULLSWAPIFNOT2";
(cell, slice, slice, int) dict_delete_get_min(cell dict, int key_len) asm(-> 0 2 1 3) "DICTREMMIN" "NULLSWAPIFNOT2";
(cell, (int, slice, int)) ~idict::delete_get_min(cell dict, int key_len) asm(-> 0 2 1 3) "DICTIREMMIN" "NULLSWAPIFNOT2";
(cell, (int, slice, int)) ~udict::delete_get_min(cell dict, int key_len) asm(-> 0 2 1 3) "DICTUREMMIN" "NULLSWAPIFNOT2";
(cell, (slice, slice, int)) ~dict::delete_get_min(cell dict, int key_len) asm(-> 0 2 1 3) "DICTREMMIN" "NULLSWAPIFNOT2";

Computes the minimum key k in dictionary dict, removes it, and returns (dict', k, x, -1), where dict' is the modified version of dict and x is the value associated with k. If the dict is empty, returns (dict, null, null, 0).

Note that the key returned by idict_delete_get_min may differ from the key returned by dict_delete_get_min and udict_delete_get_min.

dict_delete_get_max​

(cell, int, slice, int) udict_delete_get_max(cell dict, int key_len) asm(-> 0 2 1 3) "DICTUREMMAX" "NULLSWAPIFNOT2";
(cell, int, slice, int) idict_delete_get_max(cell dict, int key_len) asm(-> 0 2 1 3) "DICTIREMMAX" "NULLSWAPIFNOT2";
(cell, slice, slice, int) dict_delete_get_max(cell dict, int key_len) asm(-> 0 2 1 3) "DICTREMMAX" "NULLSWAPIFNOT2";
(cell, (int, slice, int)) ~udict::delete_get_max(cell dict, int key_len) asm(-> 0 2 1 3) "DICTUREMMAX" "NULLSWAPIFNOT2";
(cell, (int, slice, int)) ~idict::delete_get_max(cell dict, int key_len) asm(-> 0 2 1 3) "DICTIREMMAX" "NULLSWAPIFNOT2";
(cell, (slice, slice, int)) ~dict::delete_get_max(cell dict, int key_len) asm(-> 0 2 1 3) "DICTREMMAX" "NULLSWAPIFNOT2";

Computes the maximum key k in dictionary dict, removes it, and returns (dict', k, x, -1), where dict' is the modified version of dict and x is the value associated with k. If the dict is empty, returns (dict, null, null, 0).

dict_get_min?​

(int, slice, int) udict_get_min?(cell dict, int key_len) asm (-> 1 0 2) "DICTUMIN" "NULLSWAPIFNOT2";
(int, slice, int) idict_get_min?(cell dict, int key_len) asm (-> 1 0 2) "DICTIMIN" "NULLSWAPIFNOT2";

Computes the minimum key k in dictionary dict, the associated value x, and returns (k, x, -1). If the dictionary is empty, returns (null, null, 0).

dict_get_max?​

(int, slice, int) udict_get_max?(cell dict, int key_len) asm (-> 1 0 2) "DICTUMAX" "NULLSWAPIFNOT2";
(int, slice, int) idict_get_max?(cell dict, int key_len) asm (-> 1 0 2) "DICTIMAX" "NULLSWAPIFNOT2";

Computes the maximum key k in dictionary dict, the associated value x, and returns (k, x, -1). If the dictionary is empty, returns (null, null, 0).

dict_get_min_ref?​

(int, cell, int) udict_get_min_ref?(cell dict, int key_len) asm (-> 1 0 2) "DICTUMINREF" "NULLSWAPIFNOT2";
(int, cell, int) idict_get_min_ref?(cell dict, int key_len) asm (-> 1 0 2) "DICTIMINREF" "NULLSWAPIFNOT2";

Similar to dict_get_min? but returns the only reference in the value as a reference.

dict_get_max_ref?​

(int, cell, int) udict_get_max_ref?(cell dict, int key_len) asm (-> 1 0 2) "DICTUMAXREF" "NULLSWAPIFNOT2";
(int, cell, int) idict_get_max_ref?(cell dict, int key_len) asm (-> 1 0 2) "DICTIMAXREF" "NULLSWAPIFNOT2";

Similar to dict_get_max? but returns the only reference in the value as a reference.

dict_get_next?​

(int, slice, int) udict_get_next?(cell dict, int key_len, int pivot) asm(pivot dict key_len -> 1 0 2) "DICTUGETNEXT" "NULLSWAPIFNOT2";
(int, slice, int) idict_get_next?(cell dict, int key_len, int pivot) asm(pivot dict key_len -> 1 0 2) "DICTIGETNEXT" "NULLSWAPIFNOT2";

Computes the minimum key k in dictionary dict that is greater than pivot; returns k, associated value, and a flag indicating success. If the dictionary is empty, returns (null, null, 0).

dict_get_nexteq?​

(int, slice, int) udict_get_nexteq?(cell dict, int key_len, int pivot) asm(pivot dict key_len -> 1 0 2) "DICTUGETNEXTEQ" "NULLSWAPIFNOT2";
(int, slice, int) idict_get_nexteq?(cell dict, int key_len, int pivot) asm(pivot dict key_len -> 1 0 2) "DICTIGETNEXTEQ" "NULLSWAPIFNOT2";

Similar to dict_get_next? but computes the minimum key k that is greater than or equal to pivot.

dict_get_prev?​

(int, slice, int) udict_get_prev?(cell dict, int key_len, int pivot) asm(pivot dict key_len -> 1 0 2) "DICTUGETPREV" "NULLSWAPIFNOT2";
(int, slice, int) idict_get_prev?(cell dict, int key_len, int pivot) asm(pivot dict key_len -> 1 0 2) "DICTIGETPREV" "NULLSWAPIFNOT2";

Similar to dict_get_next? but computes the maximum key k smaller than pivot.

dict_get_preveq?​

(int, slice, int) udict_get_preveq?(cell dict, int key_len, int pivot) asm(pivot dict key_len -> 1 0 2) "DICTUGETPREVEQ" "NULLSWAPIFNOT2";
(int, slice, int) idict_get_preveq?(cell dict, int key_len, int pivot) asm(pivot dict key_len -> 1 0 2) "DICTIGETPREVEQ" "NULLSWAPIFNOT2";

Similar to dict_get_prev? but computes the maximum key k smaller than or equal to pivot.

new_dict​

cell new_dict() asm "NEWDICT";

Creates an empty dictionary, which is actually a null value. Special case of null().

dict_empty?​

int dict_empty?(cell c) asm "DICTEMPTY";

Checks whether a dictionary is empty. Equivalent to cell_null?.

Prefix dictionaries primitives​

TVM also supports dictionaries with non-fixed length keys which form a prefix code (i.e., there is no key that is a prefix to another key). Learn more about them in TVM.pdf.

pfxdict_get?​

(slice, slice, slice, int) pfxdict_get?(cell dict, int key_len, slice key) asm(key dict key_len) "PFXDICTGETQ" "NULLSWAPIFNOT2";

Returns (s', x, s'', -1) or (null, null, s, 0). Looks up the unique prefix of slice key present in the prefix code dictionary dict. If found, the prefix of s is returned as s' and the corresponding value (also a slice) as x. The remainder of s is returned as slice s''. If no prefix of s is key in prefix code dictionary dict, it returns the unchanged s and a zero flag to indicate failure.

pfxdict_set?​

(cell, int) pfxdict_set?(cell dict, int key_len, slice key, slice value) asm(value key dict key_len) "PFXDICTSET";

Similar to dict_set but may fail if the key is a prefix of another key presented in the dictionary. Indicating success, returns a flag.

pfxdict_delete?​

(cell, int) pfxdict_delete?(cell dict, int key_len, slice key) asm(key dict key_len) "PFXDICTDEL";

Similar to dict_delete?.

Special primitives​

null​

forall X -> X null() asm "PUSHNULL";

By the TVM type Null, FunC represents the absence of a value of some atomic type. So null can actually have any atomic type.

~impure_touch​

forall X -> (X, ()) ~impure_touch(X x) impure asm "NOP";

Mark a variable as used, such that the code which produced it won't be deleted even if it is not impure. (c.f. impure specifier)

Other primitives​

min​

int min(int x, int y) asm "MIN";

Computes the minimum of two integers x and y.

max​

int max(int x, int y) asm "MAX";

Computes the maximum of two integers x and y.

minmax​

(int, int) minmax(int x, int y) asm "MINMAX";

Sorts two integers.

abs​

int abs(int x) asm "ABS";

Computes the absolute value of the integer x.