Added `gcd` function to stdlib.
[vvhitespace] / stdlib / README.md
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1# Overview #
2
3This folder contains a library of useful functions written in VVhitespace.
4Standard include guards are used with `cpp` to include the stdlib in user
5programs. For an example, see `examples/hello-stdlib`. This also means
6`cpp` syntax must be respected.
7
8# Reservations #
9
10Since all labels share a global namespace, the standard library makes the
11following reservations:
12
13## Label ##
14
15 00000000 0xxxxxxx - reserved for stdlib function entry points
16 00000000 1xxxxxxx - available for use in user programs
17 0xxxxxxx xxxxxxxx - reserved for private use by stdlib
18 1xxxxxxx xxxxxxxx - available for use in user programs
19
20## Heap and Pointers ##
21
22The first 16 heap addresses (`0-15`) are reserved when using the stdlib.
23Within that reservation, heap[0] is used by `random` and the block
24heap[1]-heap[15] by the stack rotation subroutines which time-share
25pseudo-registers between the various stdlib subroutines.
26
27By convention, functions which return a pointer will use the address `0` to
28represent a `NULL` pointer.
29
30# Entry Points #
31
32The following labels are entry points to stdlib functions. Read the
33header comment for each function to learn the call and return stack.
34
35 000xxx - reserved
36 001xxx - core functions
37 1000 ----- printf (stdio.pvvs)
38 1001 ----- print number from stack (stdio.pvvs)
39 1010 ----- stackrotate (stack.pvvs)
40 1011 ----- stackrotatereverse (stack.pvvs)
41 1100 ----- deepdup (stack.pvvs)
42 010xxx - math functions
43 10000 ----- random (math.pvvs)
44 10001 ----- absolute value (math.pvvs)
45 10010 ----- greatest common divisor (math.pvvs)
46 011xxx - heap functions
47 11000 ----- memset (heap.pvvs)
48 11001 ----- memcpy (heap.pvvs)
49 11010 ----- memrand (heap.pvvs)
50 11011 ----- memcmp (heap.pvvs)
51 11100 ----- memsrch (heap.pvvs)
52 11101 ----- <empty>
53 11110 ----- slurp (heap.pvvs)
54 11111 ----- spew (heap.pvvs)
55 100xxx - string functions
56 100000 ----- strlen (string.pvvs)
57 101xxx - logic functions
58 101000 ----- not (logic.pvvs)
59 101001 ----- and (logic.pvvs)
60 101010 ----- or (logic.pvvs)
61 101011 ----- xor (logic.pvvs)
62 101100 ----- rshift (logic.pvvs)
63 101101 ----- lshift (logic.pvvs)
64 110xxx - conversion functions
65 111xxx - debug functions
66 111000 ----- dump heap (debug.pvvs)
67 111001 ----- dump stack (debug.pvvs)
68 111010 ----- print sign (debug.pvvs)
69 111011 ----- print magnitude (debug.pvvs)
70 111100 ----- print string (debug.pvvs)
71 111101 ----- print signed number (debug.pvvs)
72 1xxxxxx - reserved for less common entry points
73 1000000 ----- lowbitand (logic.pvvs)
74 1000001 ----- <empty>
75 1000010 ----- print sign of number (stdio.pvvs)
76 1000011 ----- print magnitude of number (stdio.pvvs)
77 1000100 ----- print string from stack (stdio.pvvs)
78 1000101 ----- print string from heap (stdio.pvvs)
79
80# Misc #
81
82## Private Label Space ##
83
84By convention, each public stdlib label will have 8 bits of private label space
85associated with it, formed as follows:
86
87 00001000 xxxxxxxx - for use by 1000
88 00001001 xxxxxxxx - for use by 1001
89 ...etc
90
91## Extending Heap Reservation ##
92
93By default, the stdlib uses the first 16 heap addresses. All heap access (other
94than heap[0] as a seed) occurs through `stackrotate` and `stackrotatereverse`.
95Edit these functions to increase the stdlib's heap reservation.
96
97The remainder of the stdlib is written to automatically use the new allocation.
98Functions like `printf`, for example, allow more substitutions when the heap
99allocation is increased.