Describe built-in Julia functions

1 files changed, 163 insertions, 1 deletions

diff --git a/docs/julia.rst b/docs/julia.rst
index 1343f706..5203b522 100644
--- a/docs/julia.rst
+++ b/docs/julia.rst
@@ -18,7 +18,7 @@ for-loops, switch-statements, expressions and assignments to variables.
 
 JULIA in itself does not even provide operators. If the EVM is targeted,
 opcodes will be available as built-in functions, but they can be reimplemented
-if the backend changes.
+if the backend changes. For a list of mandatory built-in functions, see the section below.
 
 The following example program assumes that the EVM opcodes ``mul``, ``div``
 and ``mod`` are available either natively or as functions and computes exponentiation.
@@ -187,3 +187,165 @@ For ``(S1, z) = E(S, y)`` let ``(S2, w) = E(S1, x)``. TODO
         where hex is the hexadecimal decoding function
     E(G, L, n: DecimalNumber) = G, L, dec(n),
         where dec is the decimal decoding function
+
+Low-level Functions
+-------------------
+
+The following functions must be available:
+
++---------------------------------------------------------------------------------------------------------------+
+| *Arithmetics*                                                                                                 |
++---------------------------------------------------------------------------------------------------------------+
+| add256(x:256, y:256) -> z:256               | x + y                                                           |
++---------------------------------------------------------------------------------------------------------------+
+| sub256(x:256, y:256) -> z:256               | x - y                                                           |
++---------------------------------------------------------------------------------------------------------------+
+| mul256(x:256, y:256) -> z:256               | x * y                                                           |
++---------------------------------------------------------------------------------------------------------------+
+| div256(x:256, y:256) -> z:256               | x / y                                                           |
++---------------------------------------------------------------------------------------------------------------+
+| sdiv256(x:256, y:256) -> z:256              | x / y, for signed numbers in two's complement                   |
++---------------------------------------------------------------------------------------------------------------+
+| mod256(x:256, y:256) -> z:256               | x % y                                                           |
++---------------------------------------------------------------------------------------------------------------+
+| smod256(x:256, y:256) -> z:256              | x % y, for signed numbers in two's complement                   |
++---------------------------------------------------------------------------------------------------------------+
+| signextend256(i:256, x:256) -> z:256        | sign extend from (i*8+7)th bit counting from least significant  |
++---------------------------------------------------------------------------------------------------------------+
+| exp256(x:256, y:256) -> z:256               | x to the power of y                                             |
++---------------------------------------------------------------------------------------------------------------+
+| addmod256(x:256, y:256, m:256) -> z:256     | (x + y) % m with arbitrary precision arithmetics                |
++---------------------------------------------------------------------------------------------------------------+
+| mulmod256(x:256, y:256, m:256) -> z:256     | (x * y) % m with arbitrary precision arithmetics                |
++---------------------------------------------------------------------------------------------------------------+
+| lt256(x:256, y:256) -> z:bool               | 1 if x < y, 0 otherwise                                         |
++---------------------------------------------------------------------------------------------------------------+
+| gt256(x:256, y:256) -> z:bool               | 1 if x > y, 0 otherwise                                         |
++---------------------------------------------------------------------------------------------------------------+
+| slt256(x:256, y:256) -> z:bool              | 1 if x < y, 0 otherwise, for signed numbers in two's complement |
++---------------------------------------------------------------------------------------------------------------+
+| sgt256(x:256, y:256) -> z:bool              | 1 if x > y, 0 otherwise, for signed numbers in two's complement |
++---------------------------------------------------------------------------------------------------------------+
+| eq256(x:256, y:256) -> z:bool               | 1 if x == y, 0 otherwise                                        |
++---------------------------------------------------------------------------------------------------------------+
+| not256(x:256) -> z:256                      | ~x, every bit of x is negated                                   |
++---------------------------------------------------------------------------------------------------------------+
+| and256(x:256, y:256) -> z:256               | bitwise and of x and y                                          |
++---------------------------------------------------------------------------------------------------------------+
+| or256(x:256, y:256) -> z:256                | bitwise or of x and y                                           |
++---------------------------------------------------------------------------------------------------------------+
+| xor256(x:256, y:256) -> z:256               | bitwise xor of x and y                                          |
++---------------------------------------------------------------------------------------------------------------+
+| shl256(x:256, y:256) -> z:256               | logical left shift of x by y                                    |
++---------------------------------------------------------------------------------------------------------------+
+| shr256(x:256, y:256) -> z:256               | logical right shift of x by y                                   |
++---------------------------------------------------------------------------------------------------------------+
+| sar256(x:256, y:256) -> z:256               | arithmetic right shift of x by y                                |
++---------------------------------------------------------------------------------------------------------------+
+| byte(n:256, x:256) -> v:256                 | nth byte of x, where the most significant byte is the 0th byte  |
+| Cannot this be just replaced by and256(shr256(n, x), 0xff) and let it be optimised out by the EVM backend?    |
++---------------------------------------------------------------------------------------------------------------+
+| *Memory and storage*                                                                                          |
++---------------------------------------------------------------------------------------------------------------+
+| mload(p:256) -> v:256                       | mem[p..(p+32))                                                  |
++---------------------------------------------------------------------------------------------------------------+
+| mstore(p:256, v:256)                        | mem[p..(p+32)) := v                                             |
++---------------------------------------------------------------------------------------------------------------+
+| mstore8(p:256, v:256)                       | mem[p] := v & 0xff    - only modifies a single byte             |
++---------------------------------------------------------------------------------------------------------------+
+| sload(p:256) -> v:256                       | storage[p]                                                      |
++---------------------------------------------------------------------------------------------------------------+
+| sstore(p:256, v:256)                        | storage[p] := v                                                 |
++---------------------------------------------------------------------------------------------------------------+
+| msize() -> size:256                         | size of memory, i.e. largest accessed memory index, albeit due  |
+|                                             | due to the memory extension function, which extends by words,   |
+|                                             | this will always be a multiple of 32 bytes                      |
++---------------------------------------------------------------------------------------------------------------+
+| *Execution control*                                                                                           |
++---------------------------------------------------------------------------------------------------------------+
+| create(v:256, p:256, s:256)                 | create new contract with code mem[p..(p+s)) and send v wei      |
+|                                             | and return the new address                                      |
++---------------------------------------------------------------------------------------------------------------+
+| call(g:256, a:256, v:256, in:256,           | call contract at address a with input mem[in..(in+insize))      |
+| insize:256, out:256, outsize:256) -> r:256  | providing g gas and v wei and output area                       |
+|                                             | mem[out..(out+outsize)) returning 0 on error (eg. out of gas)   |
+|                                             | and 1 on success                                                |
++---------------------------------------------------------------------------------------------------------------+
+| callcode(g:256, a:256, v:256, in:256,       | identical to `call` but only use the code from a and stay       |
+| insize:256, out:256, outsize:256) -> r:256  | in the context of the current contract otherwise                |
++---------------------------------------------------------------------------------------------------------------+
+| delegatecall(g:256, a:256, in:256,          | identical to `callcode` but also keep ``caller``                |
+| insize:256, out:256, outsize:256) -> r:256  | and ``callvalue``                                               |
++---------------------------------------------------------------------------------------------------------------+
+| stop()                                      | stop execution, identical to return(0,0)                        |
+| Perhaps it would make sense retiring this as it equals to return(0,0). It can be an optimisation by the EVM   |
+| backend.                                                                                                      |
++---------------------------------------------------------------------------------------------------------------+
+| abort()                                     | abort (equals to invalid instruction on EVM)                    |
++---------------------------------------------------------------------------------------------------------------+
+| return(p:256, s:256)                        | end execution, return data mem[p..(p+s))                        |
++---------------------------------------------------------------------------------------------------------------+
+| revert(p:256, s:256)                        | end execution, revert state changes, return data mem[p..(p+s))  |
++---------------------------------------------------------------------------------------------------------------+
+| selfdestruct(a:256)                         | end execution, destroy current contract and send funds to a     |
++---------------------------------------------------------------------------------------------------------------+
+| log0(p:256, s:256)                          | log without topics and data mem[p..(p+s))                       |
++---------------------------------------------------------------------------------------------------------------+
+| log1(p:256, s:256, t1:256)                  | log with topic t1 and data mem[p..(p+s))                        |
++---------------------------------------------------------------------------------------------------------------+
+| log2(p:256, s:256, t1:256, t2:256)          | log with topics t1, t2 and data mem[p..(p+s))                   |
++---------------------------------------------------------------------------------------------------------------+
+| log3(p:256, s:256, t1:256, t2:256,          | log with topics t, t2, t3 and data mem[p..(p+s))                |
+| t3:256)                                     |                                                                 |
++---------------------------------------------------------------------------------------------------------------+
+| log4(p:256, s:256, t1:256, t2:256,          | log with topics t1, t2, t3, t4 and data mem[p..(p+s))           |
+| t3:256, t4:256)                             |                                                                 |
++---------------------------------------------------------------------------------------------------------------+
+| *State queries*                                                                                               |
++---------------------------------------------------------------------------------------------------------------+
+| blockcoinbase() -> address:256              | current mining beneficiary                                      |
++---------------------------------------------------------------------------------------------------------------+
+| blockdifficulty() -> difficulty:256         | difficulty of the current block                                 |
++---------------------------------------------------------------------------------------------------------------+
+| blockgaslimit() -> limit:256                | block gas limit of the current block                            |
++---------------------------------------------------------------------------------------------------------------+
+| blockhash(b:256) -> hash:256                | hash of block nr b - only for last 256 blocks excluding current |
++---------------------------------------------------------------------------------------------------------------+
+| blocknumber() -> block:256                  | current block number                                            |
++---------------------------------------------------------------------------------------------------------------+
+| blocktimestamp() -> timestamp:256           | timestamp of the current block in seconds since the epoch       |
++---------------------------------------------------------------------------------------------------------------+
+| txorigin() -> address:256                   | transaction sender                                              |
++---------------------------------------------------------------------------------------------------------------+
+| txgasprice() -> price:256                   | gas price of the transaction                                    |
++---------------------------------------------------------------------------------------------------------------+
+| gasleft() -> gas:256                        | gas still available to execution                                |
++---------------------------------------------------------------------------------------------------------------+
+| balance(a:256) -> v:256                     | wei balance at address a                                        |
++---------------------------------------------------------------------------------------------------------------+
+| this() -> address:256                       | address of the current contract / execution context             |
++---------------------------------------------------------------------------------------------------------------+
+| caller() -> address:256                     | call sender (excluding delegatecall)                            |
++---------------------------------------------------------------------------------------------------------------+
+| callvalue() -> v:256                        | wei sent together with the current call                         |
++---------------------------------------------------------------------------------------------------------------+
+| calldataload(p:256) -> v:256                | call data starting from position p (32 bytes)                   |
++---------------------------------------------------------------------------------------------------------------+
+| calldatasize() -> v:256                     | size of call data in bytes                                      |
++---------------------------------------------------------------------------------------------------------------+
+| calldatacopy(t:256, f:256, s:256)           | copy s bytes from calldata at position f to mem at position t   |
++---------------------------------------------------------------------------------------------------------------+
+| codesize() -> size:256                      | size of the code of the current contract / execution context    |
++---------------------------------------------------------------------------------------------------------------+
+| codecopy(t:256, f:256, s:256)               | copy s bytes from code at position f to mem at position t       |
++---------------------------------------------------------------------------------------------------------------+
+| extcodesize(a:256) -> size:256              | size of the code at address a                                   |
++---------------------------------------------------------------------------------------------------------------+
+| extcodecopy(a:256, t:256, f:256, s:256)     | like codecopy(t, f, s) but take code at address a               |
++---------------------------------------------------------------------------------------------------------------+
+| *Others*                                                                                                      |
++---------------------------------------------------------------------------------------------------------------+
+| discard256(unused:256)                      | discard value                                                   |
++---------------------------------------------------------------------------------------------------------------+
+| sha3(p:256, s:256) -> v:256                 | keccak(mem[p...(p+s)))                                          |
++---------------------------------------------------------------------------------------------------------------+