2021-08-25 20:04:25 +00:00
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( pseudo-random number generator )
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2021-08-25 20:08:30 +00:00
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( based on 16-bit xorshift algorithm discussed on
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http://www.retroprogramming.com/2017/07/xorshift-pseudorandom-numbers-in-z80.html )
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2021-08-25 20:04:25 +00:00
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( devices )
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|00 @System [ &vector $2 &wst $1 &rst $1 &pad $4 &r $2 &g $2 &b $2 &debug $1 &halt $1 ]
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|20 @Screen [ &vector $2 &width $2 &height $2 &pad $2 &x $2 &y $2 &addr $2 &pixel $1 &sprite $1 ]
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|b0 @DateTime [ &year $2 &month $1 &day $1 &hour $1 &minute $1 &second $1 &dotw $1 &doty $2 &isdst $1 ]
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( variables )
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|0000
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( program )
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|0100 ( -> )
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( init )
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;on-frame .Screen/vector DEO2
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( seed prng (must be nonzero) )
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.DateTime/month DEI .DateTime/day DEI
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#00 .DateTime/second #a0 SFT2 EOR2
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#00 .DateTime/minute #40 SFT2 EOR2
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.DateTime/hour EOR
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ORAk ,&non-zero JCN INC2 &non-zero
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;prng/seed STA2
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( theme )
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#0fe5 .System/r DEO2
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#0fc5 .System/g DEO2
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#0f25 .System/b DEO2
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BRK
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@on-frame ( -> )
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#c0
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&loop
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,draw-pixel JSR
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INC
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DUP ,&loop JCN
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POP
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BRK
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@draw-pixel
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,prng JSR
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#00 SWP .Screen/x DEO2
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#00 SWP .Screen/y DEO2
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#01 .Screen/pixel DEO
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JMP2r
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@prng ( -- number* )
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( returns the next number in the 65,535-long sequence,
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which is never zero but every other 16-bit number
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appears once before the sequence repeats )
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,&seed LDR2
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DUP2 #70 SFT2 EOR2
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DUP2 #09 SFT2 EOR2
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DUP2 #80 SFT2 EOR2
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,&seed STR2k POP
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JMP2r
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&seed $2
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