error loading module '(' expected near '=' - lua

Question

This code is to create function listeners for the cannon shooting. When i run the code, it gave me an error Question1.lua:43 '('expected near '='
function cannonCharge = function(event)
if(event.phase == 'began') then
impulse = 0
cannon.isVisible = true
Runtime:addEventListener('enterFrame', charge)
print ('cannonCharge')
end
end
function shot = function(event)
if(event.phase == 'ended') then
Runtime:removeEventListener('enterFrame', charge)
cannon.isVisible = true
cannon.rotation = 0
cannonBall = display.newImage('cannon ball.png', 84, 220)
physics.addBody(cannonBall, {density = 1, friction = 0, bounce = 0})
cannonBalls:insert(cannonBall)
print ('shot')
-- Shoot cannon ball
cannonBall:applyLinearImpulse(3, impulse, cannonBall.x, cannonBall.y )
--Collision listener
cannonBall:addEventListener ('collision', ballCollision)
end
end
function scene:createScene(event)
...
I added the listeners to enterScene
function scene:enterScene( event )
local group = self.view
background:addEventListener('touch', cannonCharge)
background:addEventListener('touch', shot)
end

Answer 1

Variables don't have types; Only values do. So, instead of
function shot = function(event)
-- ...
end
Try
local shot = function(event)
-- ...
end
If you don't put local, the variable will be global. Use of globals should be minimized.
If you prefer a more structured syntax, you can use:
local function shot(event)
-- ...
end
That's equivalent to:
local shot
shot = function(event)
-- ...
end

Answer 2

You can not assign two touch listener on the same object. Because it's create conflict to which function it's call first.
instead of that, you need to assign one touch and one tap listener. So there is no conflict.
background:addEventListener('tap', cannonCharge)
background:addEventListener('touch', shot)