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I have a function which negotiates an agreement between two parties using a state channel, to accomplish this I need two signatures bytes32 e, uint8 v, bytes32 r, bytes32 sx2 for the state channel, and I need some variables for each persons agreement that are signed by the state.

This results in a stack too deep error. My workaround is to compress the signatures and variables into a bytes32[] array and type cast where needed. This seems dumb. Anyone have a better way?

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If you're dealing with repeated data types it's more natural to group them into arrays by type, eg

function myThing(bytes32[] es, uint8[] vs, bytes32[] rs, bytes32[] ss)

This also tends to reduce code duplication inside the function, as you will only need one line doing ecrecover, which you then repeat in a loop.

If you're still short of variables, you may also want to consider breaking part of the functionality out into another function.

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  • Its a public function that runs as one transaction. I had this thought as well but in this case it was more natural for making bytes32[]. Thanks for validating my suspicion that there really is not a much better way – OneChillDude Oct 9 '17 at 1:43
  • If the stack-too-deep error is triggered by variables you use inside the function rather than purely by the number of parameters then it may still help to split the functionality up internally. – Edmund Edgar Oct 9 '17 at 1:53
  • Is there a good reason for this limit? Technically it seems totally arbitrary. Like, I can have a dynamic length raw byte variable but I can't have 17 uint8s? – OneChillDude Oct 9 '17 at 1:56
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    See gory details here: github.com/ethereum/solidity/issues/2693 – Edmund Edgar Oct 9 '17 at 2:22

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