Hello, it's me again!
I haven't done much with macros in Nim, so I need some help.
I need to generate an if statement on runtime with data passed by the user, since I don't really want the user to have to modify the source code of my program each time they need to run it with a different file.
In the file I'm reading, there are two kinds of particles, "balls" and "minerals", and they all have IDs. Everything in a certain range is a ball, and everything in another range is a mineral. Based of the IDs, I need my function needs to determine the kind of collision that happened in each line of the file, be it BallBall, BallMineral, MineralMineral, or None as an error case. Simple enough.
I've got this function which is the basis of the logic of my program, where the give parameters say that everything under 700_000 is a ball, and that everything above 700_000 is a mineral:
proc collisionType(ids: array[2, float]): Collision =
result =
if (ids[0] < 700_000) and (ids[1] < 700_000):
BallBall
elif ((ids[0] < 700_000) and (ids[1] > 700_000)) or
((ids[0] > 700_000) and (ids[1] < 700_000)):
BallMineral
elif (ids[0] > 700_000) and (ids[1] > 700_000):
MineralMineral
else:
None # This case should never happen, raises an expression if later on if it does.
For example, let's say that we have Balls at 1..< 700_000, Minerals at 700_001..<1_400_000, Balls again at 1_400_001..<2_100_000, and Minerals from 2_100_001 onward. This is how collisionType would have to look like:
proc collisionType(ids: array[2, float]): Collision =
## This is horrible.
result =
if ((ids[0] < 700_000) and (ids[1] < 700_000)) or
((ids[0] < 700_000) and (ids[1] in 1_400_001..<2_100_000)) or
((ids[0] in 1_400_001..<2_100_000) and (ids[1] < 700_000)) or
((ids[0] in 1_400_001..<2_100_000) and (ids[1] in 1_400_001..<2_100_000)):
BallBall
elif ((ids[0] < 700_000) and (ids[1] in 700_001..<1_400_000)) or
((ids[0] in 700_001..<1_400_000) and (ids[1] < 700_000)) or
((ids[0] in 1_400_001..<2_100_000) and (ids[1] in 700_001..<1_400_000)) or
((ids[0] in 700_001..<1_400_000) and (ids[1] in 1_400_001..<2_100_000)) or
((ids[0] < 700_000) and (ids[1] > 2_100_000)) or
((ids[0] > 2_100_000) and (ids[1] < 700_000)) or
((ids[0] in 1_400_001..<2_100_000) and (ids[1] > 20_100_000)) or
((ids[0] > 20_100_000) and (ids[1] 1_400_001..<2_100_000)):
BallMineral
elif ((ids[0] in 700_001..<1_400_000) and (ids[1] in 700_001..<1_400_000)) or
((ids[0] in 700_001..<1_400_000) and (ids[1] > 2_100_001)) or
((ids[0] > 2_100_001) and (ids[1] in 700_001..<1_400_000)) or
((ids[0] > 2_100_001) and (ids[1] > 2_100_001)):
MineralMineral
else:
None
Does anyone have any ideas on how I could pull this off?
Macros do not work at runtime, but I believe I wrote something that solves your issue.
import strscans
let input ="1,700000"
type Collision = enum
none, ball, mineral
proc collisionType(ids: array[2, float], userInput: string): (Collision, Collision) =
var start, increment: int
if userInput.scanf("$i,$i", start, increment):
var steps = 0
while result[0] == none or result[1] == none:
let rng = start.float..(start.float + increment.float)
if ids[0] in rng:
case steps.mod(2):
of 1:
result[0] = mineral
of 0:
result[0] = ball
else: discard
if ids[1] in rng:
case steps.mod(2):
of 1:
result[1] = mineral
of 0:
result[1] = ball
else: discard
inc steps
start += increment
echo collisionType([10.5, 300], input)
echo collisionType([700001.0, 1000000.0], input)
echo collisionType([2.0, 100000000.0], input)
Oh well, there goes my plan out the window...
The problem is that the increments aren't always the same between the ranges :(
Oh gosh, I feel so silly. I could've come up with that on my own...
I'll have to do a few modifications, but this is a good start.
Thank you so much for your help!