Instruction.previous_instruction()

Returns a list of immediate previous instructions in the control flow graph.

previous_instruction() → APISet[Instruction]

The difference between the previous_instruction() function and previous_instructions() is that this function will return a list of immediate previous instructions of the current instruction in the CFG (control-flow-graph).

The function is intra-procedural.

For example, in the function:

function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;
        return c;
    }

for the instruction:

return c;

the function will return the instruction:

uint256 c = a - b;

Query Example

from glider import *
def query():
  instructions = Instructions().exec(1,11)

  return instructions + list(instructions[0].previous_instruction())

Output Example

"root":{4 items
"contract":string"0xd705c24267ed3c55458160104994c55c6492dfcf"
"contract_name":string"SafeMath"
"sol_function":solidity
function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;
        return c;
    }
"sol_instruction":solidity
return c
},
"root":{4 items
"contract":string"0xd705c24267ed3c55458160104994c55c6492dfcf"
"contract_name":string"SafeMath"
"sol_function":solidity
function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;
        return c;
    }
"sol_instruction":solidity
uint256 c = a - b
}

The function returns APISet, instead of APIList, in case the result of the function is used as the return value of the query it must be casted to list()