and ( w1 w2 – w ) core “and”
or ( w1 w2 – w ) core “or”
xor ( w1 w2 – w ) core “x-or”
invert ( w1 – w2 ) core “invert”
mux ( u1 u2 u3 – u ) gforth-1.0 “mux”
Multiplex: For every bit in u3: for a 1 bit, select the
corresponding bit from u1, otherwise the corresponding bit from u2.
E.g., %0011 %1100 %1010 mux gives %0110
lshift ( u1 u – u2 ) core “l-shift”
Shift u1 left by u bits.
rshift ( u1 u – u2 ) core “r-shift”
Shift u1 (cell) right by u bits, filling the shifted-in bits with zero (logical/unsigned shift).
arshift ( n1 u – n2 ) gforth-1.0 “ar-shift”
Shift n1 (cell) right by u bits, filling the shifted-in bits from the sign bit of n1 (arithmetic shift).
dlshift ( ud1 u – ud2 ) gforth-1.0 “dlshift”
Shift ud1 (double-cell) left by u bits.
drshift ( ud1 u – ud2 ) gforth-1.0 “drshift”
Shift ud1 (double-cell) right by u bits, filling the shifted-in bits with zero (logical/unsigned shift).
darshift ( d1 u – d2 ) gforth-1.0 “darshift”
Shift d1 (double-cell) right by u bits, filling the shifted-in bits from the sign bit of d1 (arithmetic shift).
2* ( n1 – n2 ) core “two-star”
Shift left by 1; also works on unsigned numbers
2/ ( n1 – n2 ) core “two-slash”
Arithmetic shift right by 1. For signed numbers this is a floored
division by 2 (note that / is symmetric on some systems, but
2/ always floors).
d2* ( d1 – d2 ) double “d-two-star”
Shift double-cell left by 1; also works on unsigned numbers
d2/ ( d1 – d2 ) double “d-two-slash”
Arithmetic shift right by 1. For signed numbers this is a floored division by 2.
>pow2 ( u1 – u2 ) gforth-1.0 “to-pow2”
u2 is the lowest power-of-2 number with u2>=u1.
log2 ( u – n ) gforth-1.0 “log2”
N is the rounded-down binary logarithm of u, i.e., the index of the first set bit; if u=0, n=-1.
pow2? ( u – f ) gforth-1.0 “pow-two-query”
f is true if and only if u is a power of two, i.e., there is exactly one bit set in u.
ctz ( x – u ) gforth-1.0 “c-t-z”
count trailing zeros in binary representation of x
Unlike most other operations, rotation of narrower units cannot easily be synthesized from rotation of wider units, so using cell-wide and double-wide rotation operations means that the results depend on the cell width. For published algorithms or cell-width-independent results, you usually need to use a fixed-width rotation operation.
wrol ( u1 u – u2 ) gforth-1.0 “wrol”
Rotate the least significant 16 bits of u1 left by u bits, set the other bits to 0.
wror ( u1 u – u2 ) gforth-1.0 “wror”
Rotate the least significant 16 bits of u1 right by u bits, set the other bits to 0.
lrol ( u1 u – u2 ) gforth-1.0 “lrol”
Rotate the least significant 32 bits of u1 left by u bits, set the other bits to 0.
lror ( u1 u – u2 ) gforth-1.0 “lror”
Rotate the least significant 32 bits of u1 right by u bits, set the other bits to 0.
rol ( u1 u – u2 ) gforth-1.0 “rol”
Rotate all bits of u1 left by u bits.
ror ( u1 u – u2 ) gforth-1.0 “ror”
Rotate all bits of u1 right by u bits.
drol ( ud1 u – ud2 ) gforth-1.0 “drol”
Rotate all bits of ud1 (double-cell) left by u bits.
dror ( ud1 u – ud2 ) gforth-1.0 “dror”
Rotate all bits of ud1 (double-cell) right by u bits.