mirror of
https://github.com/QB64-Phoenix-Edition/QB64pe.git
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6e01fc8dce
Added new _STRCMP and _STRICMP commands for quick string comparisons. Cleaned up QB64 to finish removing the QUI (quick user insert) code and folders. Altered UCASE and LCASE routines to be faster in some situations for us.
106 lines
4.3 KiB
Plaintext
106 lines
4.3 KiB
Plaintext
The '''RND''' function returns a random number with a value between 0 (inclusive) and 1 (exclusive).
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{{PageSyntax}}
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:: result! = {{KW|RND}} [(n!)]
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{{PageDescription}}
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* n! is a numeric value that defines the behavior of the RND function but is NOT normally required:
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::n! omitted: Return next random number in the sequence.
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::n! = 0: Return the last value returned.
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::n! < 0: Always returns the same value for any given n
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* Even if n! > 0, the sequence of numbers generated will not change unless [[RANDOMIZE]] is initiated.
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* The random numbers generated range from 0 to .9999999 [[SINGLE]] values that never equal 1.
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* To get values in a range larger than 1, multiply it with a number.
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* To get values starting at a certain number, add that number to the result.
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* If you need an integer range of numbers, like a dice roll, round it down to an {{KW|INT}}. Add 1 to the maximum number with INT.
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* The random sequence is 2^24 = 16,777,216 entries long, which can cause repeated patterns in some cases. For a more precise random number, you need to write your own [http://en.wikipedia.org/wiki/Linear_congruential_generator| random function].
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* Formulas for the [[INT|Integer]] or [[CINT|Closest Integer]] of ANY number range from ''min%''(lowest value) to ''max%''(greatest value):
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::* Using [[INT]]: randNum% = INT(RND * (max% - min% + 1)) + min%
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::* Using [[CINT]]: randNum% = CINT(RND * (max% - min%)) + min%
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* Use [[RANDOMIZE]] [[TIMER]] for different random number results each time a program is run.
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* [[RUN]] should reset the [[RANDOMIZE]] sequence to the starting [[RND]] function value.(Not yet in QB64)
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''Example 1:'' Generating a random integer value between 1 and 6 (inclusive) using INT.
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{{CodeStart}}
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dice% = {{Cl|INT}}({{Cl|RND}} * 6) + 1 '' '' 'add one as INT value never reaches 6
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{{CodeEnd}}
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''Example 2:'' Using uniform random numbers to create random numbers with a gaussian distribution ([http://en.wikipedia.org/wiki/Marsaglia_polar_method| Marsaglia's polar method]).
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{{CodeStart}} '' ''
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{{Cl|DO}}
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u! = {{Cl|RND}} * 2 - 1
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v! = {{Cl|RND}} * 2 - 1
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s! = u! * u! + v! * v!
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{{Cl|LOOP}} {{Cl|WHILE}} s! >= 1 {{Cl|OR}} s! = 0
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s! = SQR(-2 * {{Cl|LOG}}(s!) / s!) * 0.5
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u! = u! * s!
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v! = v! * s! '' ''
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{{CodeEnd}}
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:''Explanation:'' Values ''u!'' and ''v!'' are now two independent random numbers with gaussian distribution, centered at 0.
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''Example 3:'' Random flashes from an explosion
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{{CodeStart}} '' ''
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{{Cl|SCREEN}} {{Cl|_NEWIMAGE}}(640, 480, 32)
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{{Cl|RANDOMIZE}} {{Cl|TIMER}}
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BC = 120 ' BALL COUNT
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{{Cl|DIM}} ballx(1 {{Cl|TO}} BC)
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{{Cl|DIM}} bally(1 {{Cl|TO}} BC)
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{{Cl|DIM}} velx(1 {{Cl|TO}} BC)
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{{Cl|DIM}} vely(1 {{Cl|TO}} BC)
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{{Cl|DIM}} bsize(1 {{Cl|TO}} BC)
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Y = {{Cl|INT}}({{Cl|RND}} * (400 - 100 + 1)) + 100
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X0 = 325
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Y0 = 300
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Tmax = 150
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DO
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{{Cl|FOR...NEXT|FOR}} p = 1 {{Cl|TO}} BC
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T = {{Cl|INT}}({{Cl|RND}} * (Tmax - 50 + 1)) + 50
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X = {{Cl|INT}}({{Cl|RND}} * (1000 + 500 + 1)) - 500
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velx(p) = (X - X0) / T ' calculate velocity based on flight time
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vely(p) = -1 * (Y - .05 * (T ^ 2 + 20 * Y0)) / (T) ' verticle velocity
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{{Cl|NEXT}} p
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{{Cl|FOR...NEXT|FOR}} w = 1 {{Cl|TO}} BC
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bsize(w) = {{Cl|INT}}({{Cl|RND}} * (10 - 0 + 1)) + 0 'size
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{{Cl|NEXT}} w
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{{Cl|FOR...NEXT|FOR}} J = 1 {{Cl|TO}} Tmax
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{{Cl|_LIMIT}} 60
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{{Cl|CLS}}
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'{{Cl|FOR...NEXT|FOR}} i = 0 {{Cl|TO}} 255 {{Cl|STEP}} .5
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'{{Cl|CIRCLE}} (X0, Y0), i, {{Cl|_RGB}}(255 - i, 0, 0), 0, 3.147
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' {{Cl|NEXT}} i
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R = {{Cl|INT}}({{Cl|RND}} * (25 - 20 + 1)) + 20 'random glimmer
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{{Cl|FOR...NEXT|FOR}} z = 1 {{Cl|TO}} BC
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ballx(z) = X0 + velx(z) * J
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bally(z) = Y0 - vely(z) * J + .5 * .1 * J ^ 2
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{{Cl|NEXT}} z
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{{Cl|FOR...NEXT|FOR}} d = 1 {{Cl|TO}} BC
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RCOL = {{Cl|INT}}({{Cl|RND}} * (255 - 0 + 1)) 'color
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{{Cl|FOR...NEXT|FOR}} i = 0 {{Cl|TO}} bsize(d) + 1 {{Cl|STEP}} .4 'draw balls
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{{Cl|CIRCLE}} (ballx(d), bally(d)), i, {{Cl|_RGBA}}(255, RCOL - (R * i), RCOL - R * i, 255)
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{{Cl|NEXT}} i
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{{Cl|NEXT}} d
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{{Cl|_DISPLAY}}
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{{Cl|NEXT}} J
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{{Cl|LOOP}} {{Cl|UNTIL}} {{Cl|INKEY$}} <> "" '' ''
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{{CodeEnd}} {{small|Code by Falcon}}
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{{PageSeeAlso}}
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* [[RANDOMIZE]]
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* [[TIMER]]
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* [[INT]]
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{{PageNavigation}} |