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15 lines
561 B
Markdown
15 lines
561 B
Markdown
# CDR CODING in cons cells
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The cdr-code is a 4-bit field of a 32-bit cons cell.
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It is treated as an on-page indicator bit and a 3-bit scaled offset.
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Certain combinations are treated specially.
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on-page| offset | interpretation
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-------|--------|----------------------------------------------------------------------------
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1 | 0 | CDR is NIL
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1 | 1 - 7 | CDR is at 2*offset (counted in 32-bit cells) on same page
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0 | 0 | CDR is indirect, CDR(car)
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0 | 1 - 7 | CDR is not a cons cell but is in the car of cell at 2*offset on same page
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