Routines
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47120: Check Distance
Used by the routines at HandleMoneyBag, HandleTumbleweed, HandleHorse, HandleCactus, HandlePointer and HandleBystander.
Checks whether an object is within a number of cells of the sheriff, both across and up the screen.
Input
C The distance in cells
IX The address of the object
Output
F The carry flag is set if the object is closer than that
Compare the horizontal cells.
CheckDistance 47120 LD A,(41599) Fetch the horizontal cell of the sheriff from 41599.
47123 SUB (IX+2) Subtract the horizontal cell of the object.
47126 JP P,CheckDistance_CompareHorizontal Jump to CheckDistance_CompareHorizontal if the difference is not negative.
47129 NEG Make the difference positive.
CheckDistance_CompareHorizontal 47131 CP C Compare it with the distance.
47132 RET NC Return if the object is too far away.
Compare the vertical cells.
47133 LD A,(41601) Fetch the vertical cell of the sheriff from 41601.
47136 SUB (IX+4) Subtract the vertical cell of the object.
47139 JP P,CheckDistance_CompareVertical Jump to CheckDistance_CompareVertical if the difference is not negative.
47142 NEG Make the difference positive.
CheckDistance_CompareVertical 47144 CP C Compare it with the distance.
47145 RET Return.
View the equivalent code in;
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