473 lines
12 KiB
C
473 lines
12 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "tool/build/emubin/lisp.h"
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#define TRACE 0 // print eval input output
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#define RETRO 1 // auto capitalize input
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#define ERRORS 1 // print messages or undefined behavior
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#define DELETE 1 // allow backspace to rub out symbol
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#define QUOTES 1 // allow 'X shorthand (QUOTE X)
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#define MUTABLE 0 // allow setting globals
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#define PROMPT 1 // show repl prompt
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#define WORD short
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#define WORDS 8192
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/*───────────────────────────────────────────────────────────────────────────│─╗
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│ The LISP Challenge § LISP Machine ─╬─│┼
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╚────────────────────────────────────────────────────────────────────────────│*/
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#define ATOM 0
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#define CONS 1
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#define NIL 0
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#define ATOM_T 8
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#define ATOM_QUOTE 12
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#define ATOM_ATOM 24
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#define ATOM_EQ 34
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#define ATOM_COND 40
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#define ATOM_CAR 50
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#define ATOM_CDR 58
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#define ATOM_CONS 66
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#define ATOM_LAMBDA 76
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#define ATOM_SET 90
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#define Quote(x) List(ATOM_QUOTE, x)
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#define List(x, y) Cons(x, Cons(y, NIL))
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#define Caar(x) Car(Car(x)) // ((A B C D) (E F G) H I) → A
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#define Cdar(x) Cdr(Car(x)) // ((A B C D) (E F G) H I) → (B C D)
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#define Cadar(x) Cadr(Car(x)) // ((A B C D) (E F G) H I) → B
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#define Caddar(x) Caddr(Car(x)) // ((A B C D) (E F G) H I) → C
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#define Cadr(x) Car(Cdr(x)) // ((A B C D) (E F G) H I) → (E F G)
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#define Caddr(x) Cadr(Cdr(x)) // ((A B C D) (E F G) H I) → H
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#define BOOL(x) ((x) ? ATOM_T : NIL)
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#define VALUE(x) ((x) >> 1)
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#define PTR(i) ((i) << 1 | CONS)
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struct Lisp {
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WORD mem[WORDS];
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unsigned char syntax[256];
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WORD look;
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WORD globals;
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WORD index;
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char token[128];
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long jb[8];
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char str[WORDS];
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};
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_Static_assert(sizeof(struct Lisp) <= 0x7c00 - 0x600,
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"LISP Machine too large for real mode");
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_Alignas(char) const char kSymbols[] = "NIL\0"
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"T\0"
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"QUOTE\0"
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"ATOM\0"
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"EQ\0"
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"COND\0"
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"CAR\0"
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"CDR\0"
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"CONS\0"
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"LAMBDA\0"
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"SET\0";
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#ifdef __REAL_MODE__
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static struct Lisp *const q;
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#else
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static struct Lisp q[1];
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#endif
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static void Print(long);
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static WORD GetList(void);
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static WORD GetObject(void);
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static void PrintObject(long);
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static WORD Eval(long, long);
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static void SetupSyntax(void) {
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unsigned char *syntax = q->syntax;
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asm("" : "+bSD"(syntax));
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syntax[' '] = ' ';
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syntax['\r'] = ' ';
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syntax['\n'] = ' ';
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syntax['('] = '(';
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syntax[')'] = ')';
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syntax['.'] = '.';
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#if QUOTES
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syntax['\''] = '\'';
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#endif
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}
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static inline WORD Car(long x) {
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return PEEK_ARRAY(q, mem, VALUE(x), 0);
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}
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static inline WORD Cdr(long x) {
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return PEEK_ARRAY(q, mem, VALUE(x), 1);
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}
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static WORD Set(long i, long k, long v) {
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POKE_ARRAY(q, mem, VALUE(i), 0, k);
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POKE_ARRAY(q, mem, VALUE(i), 1, v);
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return i;
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}
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static WORD Cons(WORD car, WORD cdr) {
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int i, cell;
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i = q->index;
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POKE_ARRAY(q, mem, i, 0, car);
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POKE_ARRAY(q, mem, i, 1, cdr);
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q->index = i + 2;
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cell = OBJECT(CONS, i);
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return cell;
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}
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static void SetupBuiltins(void) {
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CopyMemory(q->str, kSymbols, sizeof(kSymbols));
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q->mem[0] = PTR(2);
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q->globals = PTR(0);
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q->index = 4;
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}
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static char *StpCpy(char *d, char *s) {
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char c;
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do {
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c = LODS(s); /* a.k.a. c = *s++; */
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STOS(d, c); /* a.k.a. *d++ = c; */
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} while (c);
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return d;
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}
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WORD Intern(char *s) {
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int j, cx;
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char c, *z, *t;
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z = q->str;
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c = LODS(z);
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while (c) {
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for (j = 0;; ++j) {
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if (c != PEEK(s, j, 0)) {
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break;
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}
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if (!c) {
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return OBJECT(ATOM, z - q->str - j - 1);
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}
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c = LODS(z);
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}
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while (c) c = LODS(z);
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c = LODS(z);
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}
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--z;
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StpCpy(z, s);
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return OBJECT(ATOM, SUB((long)z, q->str));
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}
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forceinline unsigned char XlatSyntax(unsigned char b) {
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return PEEK_ARRAY(q, syntax, b, 0);
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}
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static void PrintString(char *s) {
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char c;
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for (;;) {
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if (!(c = PEEK(s, 0, 0))) break;
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PrintChar(c);
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++s;
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}
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}
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static int GetChar(void) {
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int c;
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c = ReadChar();
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#if RETRO
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if (c >= 'a') {
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CompilerBarrier();
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if (c <= 'z') c -= 'a' - 'A';
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}
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#endif
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#if DELETE
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if (c == '\b') return c;
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#endif
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PrintChar(c);
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if (c == '\r') PrintChar('\n');
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return c;
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}
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static void GetToken(void) {
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char *t;
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unsigned char b;
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b = q->look;
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t = q->token;
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while (XlatSyntax(b) == ' ') {
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b = GetChar();
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}
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if (XlatSyntax(b)) {
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STOS(t, b);
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b = GetChar();
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} else {
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while (b && !XlatSyntax(b)) {
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if (!DELETE || b != '\b') {
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STOS(t, b);
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} else if (t > q->token) {
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PrintString("\b \b");
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if (t > q->token) --t;
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}
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b = GetChar();
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}
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}
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STOS(t, 0);
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q->look = b;
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}
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static WORD ConsumeObject(void) {
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GetToken();
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return GetObject();
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}
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static WORD GetQuote(void) {
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return Quote(ConsumeObject());
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}
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static WORD AddList(WORD x) {
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return Cons(x, GetList());
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}
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static WORD GetList(void) {
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GetToken();
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switch (*q->token & 0xFF) {
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default:
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return AddList(GetObject());
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case ')':
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return NIL;
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case '.':
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return ConsumeObject();
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#if QUOTES
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case '\'':
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return AddList(GetQuote());
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#endif
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}
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}
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static WORD GetObject(void) {
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switch (*q->token & 0xFF) {
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default:
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return Intern(q->token);
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case '(':
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return GetList();
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#if QUOTES
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case '\'':
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return GetQuote();
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#endif
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}
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}
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static WORD ReadObject(void) {
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q->look = GetChar();
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GetToken();
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return GetObject();
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}
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static WORD Read(void) {
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return ReadObject();
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}
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static void PrintAtom(long x) {
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PrintString(q->str + VALUE(x));
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}
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static void PrintList(long x) {
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#if QUOTES
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if (Car(x) == ATOM_QUOTE) {
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PrintChar('\'');
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PrintObject(Cadr(x));
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return;
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}
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#endif
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PrintChar('(');
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PrintObject(Car(x));
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while ((x = Cdr(x))) {
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if (TYPE(x) == CONS) {
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PrintChar(' ');
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PrintObject(Car(x));
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} else {
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PrintString(" . ");
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PrintObject(x);
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break;
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}
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}
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PrintChar(')');
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}
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static void PrintObject(long x) {
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if (TYPE(x) == ATOM) {
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PrintAtom(x);
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} else {
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PrintList(x);
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}
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}
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static void Print(long i) {
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PrintObject(i);
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PrintString("\r\n");
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}
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__attribute__((__noreturn__)) static void Reset(void) {
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longjmp(q->jb, 1);
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}
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__attribute__((__noreturn__)) static void OnArity(void) {
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PrintString("ARITY!\n");
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Reset();
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}
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__attribute__((__noreturn__)) static void OnUndefined(long x) {
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PrintString("UNDEF! ");
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Print(x);
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Reset();
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}
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#if !ERRORS
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#define OnArity() __builtin_unreachable()
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#define OnUndefined(x) __builtin_unreachable()
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#endif
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/*───────────────────────────────────────────────────────────────────────────│─╗
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│ The LISP Challenge § Bootstrap John McCarthy's Metacircular Evaluator ─╬─│┼
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╚────────────────────────────────────────────────────────────────────────────│*/
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static WORD Atom(long x) {
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return BOOL(TYPE(x) == ATOM);
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}
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static WORD Null(long x) {
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return BOOL(!x);
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}
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static WORD Eq(long x, long y) {
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return BOOL(x == y);
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}
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static WORD Arg1(long e, long a) {
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return Eval(Cadr(e), a);
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}
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static WORD Arg2(long e, long a) {
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return Eval(Caddr(e), a);
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}
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static WORD Append(long x, long y) {
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return Null(x) ? y : Cons(Car(x), Append(Cdr(x), y));
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}
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static WORD Evcon(long c, long a) {
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return Eval(Caar(c), a) ? Eval(Cadar(c), a) : Evcon(Cdr(c), a);
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}
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static WORD Evlis(long m, long a) {
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return m ? Cons(Eval(Car(m), a), Evlis(Cdr(m), a)) : NIL;
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}
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static WORD Assoc(long x, long y) {
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if (!y) OnUndefined(x);
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return Eq(Caar(y), x) ? Cdar(y) : Assoc(x, Cdr(y));
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}
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static WORD Pair(long x, long y) {
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if (Null(x) && Null(y)) {
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return NIL;
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} else if (!Atom(x) && !Atom(y)) {
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return Cons(Cons(Car(x), Car(y)), Pair(Cdr(x), Cdr(y)));
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} else {
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OnArity();
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}
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}
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static WORD Evaluate(long e, long a) {
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if (Atom(e)) {
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return Assoc(e, a);
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} else if (Atom(Car(e))) {
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switch (Car(e)) {
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case ATOM_QUOTE:
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return Cadr(e);
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case ATOM_ATOM:
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return Atom(Arg1(e, a));
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case ATOM_EQ:
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return Eq(Arg1(e, a), Arg2(e, a));
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case ATOM_COND:
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return Evcon(Cdr(e), a);
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case ATOM_CAR:
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return Car(Arg1(e, a));
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case ATOM_CDR:
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return Cdr(Arg1(e, a));
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case ATOM_CONS:
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return Cons(Arg1(e, a), Arg2(e, a));
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#if MUTABLE
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case ATOM_SET:
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return Cdar(Set(a, Cons(Arg1(e, a), Arg2(e, a)), Cons(Car(a), Cdr(a))));
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#endif
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default:
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return Eval(Cons(Assoc(Car(e), a), Evlis(Cdr(e), a)), a);
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}
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} else if (Eq(Caar(e), ATOM_LAMBDA)) {
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return Eval(Caddar(e), Append(Pair(Cadar(e), Evlis(Cdr(e), a)), a));
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} else {
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OnUndefined(Caar(e));
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}
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}
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static WORD Eval(long e, long a) {
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WORD r;
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#if TRACE
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PrintString("->");
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Print(e);
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PrintString(" ");
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Print(a);
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#endif
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e = Evaluate(e, a);
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#if TRACE
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PrintString("<-");
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Print(e);
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#endif
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return e;
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}
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/*───────────────────────────────────────────────────────────────────────────│─╗
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│ The LISP Challenge § User Interface ─╬─│┼
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╚────────────────────────────────────────────────────────────────────────────│*/
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void Repl(void) {
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#if ERRORS
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setjmp(q->jb);
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#endif
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for (;;) {
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#if PROMPT
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PrintString("* ");
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#endif
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Print(Eval(Read(), q->globals));
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}
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}
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int main(int argc, char *argv[]) {
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/* RawMode(); */
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SetupSyntax();
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SetupBuiltins();
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#if PROMPT
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PrintString("THE LISP CHALLENGE V1\r\n"
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"VISIT GITHUB.COM/JART\r\n");
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#endif
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Repl();
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return 0;
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}
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