#A4# #Iron (.ads only)# ## #This is the ONLY machine-dependent section in FFA. # #MachineBitness# #Positive# #64# #32 or 64 depending on your system.# #MachineBitnessLog2# #Positive# #6# #log2(MachineBitness)# #ByteBits# #Positive# #8# ## ## #Words (.ads only)# ## #What the iron can work directly with - essentially register-size. Numbers in FFA are arrays of Words.# #Bitness# #Positive# #Iron.MachineBitness# #The bitness of a word is same as bitness of the iron itself. # #BitnessLog2# #Positive# #Iron.MachineBitnessLog2# ## #Byteness# #Positive# #Iron.MachineBitness/Iron.ByteBits# #Length of a Word in bytes (rather than bits).# #Type Word# ## #mod 2**Bitness# #Word as a modular type i.e. values guaranteed to ALWAYS fit the exact number of bits in use.# #Type WBool# ## #Word range 0..1# #Boolean represented as a Word, with guaranteed 0/1 values.# #Subtype WBit_Index# ## #Natural range 0 .. Bitness - 1# #All valid values for the position of a bit in a Word. # #Word_Ops# ## #Fundamental operations on the "unit" of a FFA integer: the Word.# #W_Carry# ## #WBool# #The carry (overflow) (0 or 1, hence W_Bool) of A+B that resulted in S.# #A# #Word# ## ## #B# #Word# ## ## #S# #Word# ## ## #W_Borrow# ## #WBool# #The borrow (underflow) for A-B that resulted in D.# #A# #Word# ## ## #B# #Word# ## ## #D# #Word# ## ## #W_Mux# ## #Word# #The branch-free "IF". A sel=0 returns A while Sel=1 returns B. Fundamental mechanism for FFA.# #A# #Word# ## ## #B# #Word# ## ## #Sel# #WBool# ## ## #W_Swap# ## ## #Swaps values of A and B.# #A# #Word# ## ## #B# #Word# ## ## #W_Shifts (.ads only)# ## #Imports from GNAT to have left/right shift and rotate for Words.# #Shift_Left# ## #Word# ## #Value# #Word# ## ## #Amount# #Natural# ## #Number of bit-positions to shift by.# #Shift_Right# ## #Word# ## #Value# #Word# ## ## #Amount# #Natural# ## #Number of positions to shift by.# #Rotate_Left# ## #Word# ## #Value# #Word# ## ## #Amount# #Natural# ## #Number of bit-positions to rotate by.# #Rotate_Right# ## #Word# ## #Value# #Word# ## ## #Amount# #Natural# ## #Number of bit-positions to rotate by.# #FZ_Type (.ads only)# ## #The FFA integer: an unsigned integer of fixed length, stored as a fixed-size array of Words.# #Type Indices# ## #new Natural# #Meant as generic index of anything that admits indexing at all.# #Subtype Word_Index# ## #Indices# #Meant for all valid positions of a Word inside a FFA number.# #Subtype FZBit_Index# ## #is Indices# #All valid values of a position of a bit (so not word but single bit) inside a FFA number.# #Type FZ# ## #array( Word_Index range<> ) of Word# #The representation of a FFA number.# #Subtype Word_Count# ## #Indices range 1..Indices'Last# #All valid values that may represent the number of Words in a FFA number at some given time. NB: this makes it clear that a FFA number at any given time has AT LEAST 1 Word!# #FZ_Arith# ## #Arithmetic operations with FFA numbers.# #FZ_Add# ## ## ## #X# #FZ# ## ## #Y# #FZ# ## ## #Sum# #FZ# ## ## #Overflow# #WBool# ## ## #FZ_Sub# ## ## ## #X# #FZ# ## ## #Y# #FZ# ## ## #Difference# #FZ# ## ## #Underflow# #WBool# ## ##