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math.bitwise: I can't implement ``bitfield*`` as ``reverse bitfield`` 

I don't really know why. Add some tests in the docs and document bitfield*
master
Doug Coleman 2020-06-12 19:24:02 -05:00
parent c87811f611
commit a7b058bed1
2 changed files with 60 additions and 7 deletions
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62
basis/math/bitwise/bitwise-docs.factor
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@ -6,11 +6,11 @@ IN: math.bitwise
HELP: bitfield
{ $values { "values..." "a series of objects on the stack" } { "bitspec" "an array" } { "n" integer } }
{ $description "Constructs an integer (bit field) from a series of values on the stack together with a bit field specifier, which is an array whose elements have one of the following shapes:"
{ $list
{ { $snippet "{ word shift }" } " - " { $snippet "word" } " is applied to the top of the stack and the result is shifted to the left by " { $snippet "shift" } " bits and bitor'd with the bit field" }
{ { $snippet "shift" } " - the top of the stack is shifted to the left by " { $snippet "shift" } " bits and bitor'd with the bit field" }
{ { $snippet "{ constant shift }" } " - " { $snippet "constant" } " is shifted to the left by " { $snippet "shift" } " bits and bitor'd with the bit field" }
}
{ $list
{ { $snippet "{ word shift }" } " - " { $snippet "word" } " is applied to the top of the stack and the result is shifted to the left by " { $snippet "shift" } " bits and bitor'd with the bit field" }
{ { $snippet "shift" } " - the top of the stack is shifted to the left by " { $snippet "shift" } " bits and bitor'd with the bit field" }
{ { $snippet "{ constant shift }" } " - " { $snippet "constant" } " is shifted to the left by " { $snippet "shift" } " bits and bitor'd with the bit field" }
}
"The bit field specifier is processed left to right, so stack values should be supplied in reverse order." }
{ $examples
"Consider the following specification:"
@ -21,7 +21,10 @@ HELP: bitfield
{ "bits 16-20 are set to the value of " { $snippet "fooify" } " applied to " { $snippet "z" } }
}
"Such a bit field construction can be specified with a word like the following:"
{ $code
{ $example
"USING: math math.bitwise prettyprint ;"
"IN: math.bitwise.examples"
": fooify ( x -- y ) 0b1111 bitand ;"
": baz-bitfield ( x y z -- n )"
" {"
" { fooify 16 }"
@ -29,6 +32,53 @@ HELP: bitfield
" 11"
" 0"
" } bitfield ;"
"3 2 1 baz-bitfield ."
"102403"
}
"Square the 3 from the stack and shift 8, place the 1 from the stack at bit 5, and shift a constant 1 to bit 2:"
{ $example
"USING: math math.bitwise prettyprint ;"
"1 3"
" {"
" { sq 8 }"
" 5"
" { 1 2 }"
" } bitfield .b"
"0b100100100100"
}
} ;
HELP: bitfield*
{ $values { "values..." "a series of objects on the stack" } { "bitspec" "an array" } { "n" integer } }
{ $description "Constructs an integer (bit field) from a series of values on the stack together with a bit field specifier, which is an array whose elements have one of the following shapes:"
{ $list
{ { $snippet "{ word shift }" } " - " { $snippet "word" } " is applied to the top of the stack and the result is shifted to the left by " { $snippet "shift" } " bits and bitor'd with the bit field" }
{ { $snippet "shift" } " - the top of the stack is shifted to the left by " { $snippet "shift" } " bits and bitor'd with the bit field" }
{ { $snippet "{ constant shift }" } " - " { $snippet "constant" } " is shifted to the left by " { $snippet "shift" } " bits and bitor'd with the bit field" }
}
"The bit field specifier is processed left to right, so stack values should be supplied in reverse order." }
{ $examples
"Consider the following specification:"
{ $list
{ "bits 0-10 are set to the value of " { $snippet "x" } }
{ "bits 11-14 are set to the value of " { $snippet "y" } }
{ "bit 15 is always on" }
{ "bits 16-20 are set to the value of " { $snippet "fooify" } " applied to " { $snippet "z" } }
}
"Such a bit field construction can be specified with a word like the following:"
{ $example
"USING: math math.bitwise prettyprint ;"
"IN: math.bitwise.examples"
": fooify ( x -- y ) 0b1111 bitand ;"
": baz-bitfield* ( x y z -- n )"
" {"
" 0"
" 11"
" { 1 15 }"
" { fooify 16 }"
" } bitfield* ;"
"1 2 3 baz-bitfield* ."
"233473"
}
"Square the 3 from the stack and shift 8, place the 1 from the stack at bit 5, and shift a constant 1 to bit 2:"
{ $example

5
basis/math/bitwise/bitwise.factor
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@ -76,7 +76,10 @@ MACRO: bitfield ( bitspec -- quot )
] if-empty ;
MACRO: bitfield* ( bitspec -- quot )
reverse bitfield ;
reverse
[ [ 0 ] ] [
[ (bitfield-quot) ] [ '[ @ _ dip bitor ] ] map-reduce
] if-empty ;
! bit-count
<PRIVATE