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  ANSI Common Lisp   12 Numbers   12.2 Dictionary of Numbers

12.2.63 logbitp Function

Syntax:
logbitp index integer    generalized-boolean

Arguments and Values:
index - a non-negative integer.

integer - an integer.

generalized-boolean - a generalized boolean.

Description:
logbitp is used to test the value of a particular bit in integer, that is treated as if it were binary. The value of logbitp is true if the bit in integer whose index is index (that is, its weight is 2index) is a one-bit; otherwise it is false.

Negative integers are treated as if they were in two's-complement notation.

Examples:
 (logbitp 1 1)  false
 (logbitp 0 1)  true
 (logbitp 3 10)  true
 (logbitp 1000000 -1)  true
 (logbitp 2 6)  true
 (logbitp 0 6)  false

Exceptional Situations:
Should signal an error of type type-error if index is not a non-negative integer. Should signal an error of type type-error if integer is not an integer.

Notes:
 (logbitp k n) ==(ldb-test (byte 1 k) n)

Allegro CL Implementation Details:
None.

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