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Topic: 0067: Strange 'if' problem... (Read 260 times) |
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rgovostes
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0067: Strange 'if' problem...
« on: Dec 20th, 2003, 2:27am » |
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I have this nugget of code in my program:
Code:class EssWave {
float mAcceleration = random(1.0);
if (random(2) == 1) { mAcceleration = 1.0 / (1.0 / mAcceleration); }
float mFlipSign = 1.0 + (rnd(2) * -2.0);
float Value(float d) {
return ((2.0 / (mAcceleration * sq(d) + 1.0)) - 1.0) * mFlipSign;
}
} |
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Nothing too complicated... When you instantiate the class, it picks a few random values for an EssWave, then lets you find values of positions on the wave (think of it as f(x) ...)
Now, my problem is that it expects a right curly bracket before the 'if' statement. If I change the top part to just the following:
Code:class EssWave {
float mAcceleration = random(1.0);
mAcceleration = 1.0 / (1.0 / mAcceleration); |
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It doesn't know what mAcceleration is! I cannot figure out what the problem is, and I was tempted to post this under the Software Bugs section - but, how would something this big escape others?
Please help! Thank you in advance,
Ryan Govostes
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rgovostes
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Re: 0067: Strange 'if' problem...
« Reply #1 on: Dec 20th, 2003, 5:48am » |
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Apparently you need to have code that executes when you instantiate the object. So, the following runs successfully:
Code:class EssWave {
float mAcceleration;
float mFlipSign;
EssWave() {
mAcceleration = random(1.0);
if (random(2) == 1) { mAcceleration = 1.0 / (1.0 / mAcceleration); }
float mFlipSign = 1 + (random(2) * -2);
}
float Value(float d) {
return ((2.0 / (mAcceleration * sq(d) + 1.0)) - 1.0) * mFlipSign;
}
} |
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However, I'm not sure why random(2) returns a float, as it is passed an integer.
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Bijeoma
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Re: 0067: Strange 'if' problem...
« Reply #2 on: Dec 20th, 2003, 10:20pm » |
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random(2) returns a float between 0.0-2.0
(int) random(2) will return 0 1 or 2.
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| « Last Edit: Dec 20th, 2003, 10:23pm by Bijeoma » |
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TomC
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Re: 0067: Strange 'if' problem...
« Reply #3 on: Dec 21st, 2003, 12:42am » |
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on Dec 20th, 2003, 10:20pm, Bijeoma wrote:random(2) returns a float between 0.0-2.0
(int) random(2) will return 0 1 or 2.
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Erm... true. I think eventually you might get a 2 from that. But you're way more likely to just get a 1 or a 0.
Example:
Code:
void setup() {
int zeroes = 0;
int ones = 0;
int twos = 0;
int r = 0;
while (twos == 0) {
r = (int)random(2);
if (r == 0) zeroes++;
else if (r == 1) ones++;
else if (r == 2) twos++;
}
println("zeroes : " + zeroes);
println("ones : " + ones);
println("twos : " + twos);
}
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For 4 sample runs I get...
zeroes : 14948867
ones : 14951540
twos : 1
zeroes : 19445847
ones : 19446226
twos : 1
zeroes : 34047315
ones : 34045484
twos : 1
zeroes : 6974995
ones : 6977114
twos : 1
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| « Last Edit: Dec 21st, 2003, 12:43am by TomC » |
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Bijeoma
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Re: 0067: Strange 'if' problem...
« Reply #4 on: Dec 21st, 2003, 12:48am » |
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true i shouldve pointed that out
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| « Last Edit: Dec 21st, 2003, 12:49am by Bijeoma » |
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