Objective

Implement point_distance2, which takes two point structs by value and returns the squared distance between them as a long.

Steps

• The type is given to you at the top of the file: typedef struct point { int x; int y; } point;. Do not redefine it and do not reorder the fields. The grading harness declares the same struct on its side, so a changed layout breaks the call.
• Return (a.x - b.x) squared plus (a.y - b.y) squared. No square root is involved, the answer is the square of the distance.
• a and b arrive as copies. Assigning to a.x inside your function is legal and leaves the caller's struct as it was.
• Widen to long before you subtract, then multiply the two long differences. (long)(a.x - b.x) widens too late: the subtraction already ran in int and a difference of two far apart coordinates does not fit there.
• That widening is the reason the return type is long. An int tops out a little above two billion, and squaring a coordinate of that size already lands past four quintillion.
• Two identical points return 0.
• The result is symmetric. point_distance2(a, b) and point_distance2(b, a) agree, because squaring a difference throws its sign away.
• Negative coordinates are ordinary input. Points sitting on one axis are too, one of the two differences is then 0.
• Grademe prints your return value with %ld.

Objective

Implement point_distance2, which takes two point structs by value and returns the squared distance between them as a long.

Steps

• The type is given to you at the top of the file: typedef struct point { int x; int y; } point;. Do not redefine it and do not reorder the fields. The grading harness declares the same struct on its side, so a changed layout breaks the call.
• Return (a.x - b.x) squared plus (a.y - b.y) squared. No square root is involved, the answer is the square of the distance.
• a and b arrive as copies. Assigning to a.x inside your function is legal and leaves the caller's struct as it was.
• Widen to long before you subtract, then multiply the two long differences. (long)(a.x - b.x) widens too late: the subtraction already ran in int and a difference of two far apart coordinates does not fit there.
• That widening is the reason the return type is long. An int tops out a little above two billion, and squaring a coordinate of that size already lands past four quintillion.
• Two identical points return 0.
• The result is symmetric. point_distance2(a, b) and point_distance2(b, a) agree, because squaring a difference throws its sign away.
• Negative coordinates are ordinary input. Points sitting on one axis are too, one of the two differences is then 0.
• Grademe prints your return value with %ld.