Add ability to do branching via gotos, labels and conditionals

[Philogy]

Currently BALLS only supports continuous code to avoid having to write as much Huff it'd be useful to support some basic constructs that make branching possible:

• labels: labels allow marking a certain part of the code as a possible control flow arrival point, separating logic into before/after (EVM: JUMPDEST)
• gotos: jumps to a label unconditionally (EVM: JUMP)
• conditional gotos: just a conditional goto, accepts a value and jumps if the value is non-zero (EVM: JUMPI)

[eugenioclrc]

Quick idea about this, what if you just add a simple modifier?, example:

// simple example
fn ACTION(condition, param0, param1) -> () SKIP_IF(condition) {
  ...
}
// more complex example
fn MINT(account, amount) -> () SKIP_IF(or(iszero(account), iszero(amount)) {
  ...
}

This will be transpiled as:

#define macro ACTION() = takes(3) returns(0) {
    // takes:                      [param1, param0, condition]
    // will skip if condition
    dup1 actionSkipIf jumpi

    // stuff
    
    actionSkipIf:
    pop
    pop
    pop
}

#define macro MINT() = takes(2) returns(0) {
    // takes:                      [amount, account]
    // will skip if or(iszero(account), iszero(amount)
    // solve condition first
    dup2 iszero // [amount, account, iszero(amount)]
    dup2 iszero // [amount, account, iszero(amount), iszero(account)]
    or
   mintSkitIf jumpi
    // stuff
    mintSkitIf:
    pop
    pop
}

[Philogy]

Seems a bit limited with similar effort to implement, no? Doesn't let you do direct jumps which would be required to simulate else blocks