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|
/*
* ell.c: an experimental little language
*
* Copyright (c) 2017, Přemysl Eric Janouch <p@janouch.name>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>
#include <stdarg.h>
#include <stdbool.h>
#include <setjmp.h>
#if defined __GNUC__
#define ELL_ATTRIBUTE_PRINTF(x, y) __attribute__ ((format (printf, x, y)))
#else // ! __GNUC__
#define ELL_ATTRIBUTE_PRINTF(x, y)
#endif // ! __GNUC__
#define ELL_N_ELEMENTS(a) (sizeof (a) / sizeof ((a)[0]))
// --- Utilities ---------------------------------------------------------------
static char *ell_format (const char *format, ...) ELL_ATTRIBUTE_PRINTF (1, 2);
static char *
ell_vformat (const char *format, va_list ap) {
va_list aq;
va_copy (aq, ap);
int size = vsnprintf (NULL, 0, format, aq);
va_end (aq);
if (size < 0)
return NULL;
char *buf = malloc (size + 1);
if (buf && vsnprintf (buf, size + 1, format, ap) < 0) {
free (buf);
return NULL;
}
return buf;
}
static char *
ell_format (const char *format, ...) {
va_list ap;
va_start (ap, format);
char *result = ell_vformat (format, ap);
va_end (ap);
return result;
}
// --- Generic buffer ----------------------------------------------------------
struct ell_buffer {
char *s; ///< Buffer data
size_t alloc, len; ///< Number of bytes allocated and used
bool memory_failure; ///< Memory allocation failed
};
static struct ell_buffer
ell_buffer_make (void) {
return (struct ell_buffer) { NULL, 0, 0, false };
}
static bool
ell_buffer_append (struct ell_buffer *self, const void *s, size_t n) {
if (self->memory_failure)
return false;
if (!self->s)
self->s = malloc (self->alloc = 8);
while (self->len + n > self->alloc)
self->s = realloc (self->s, self->alloc <<= 1);
if (!self->s) {
self->memory_failure = true;
return false;
}
memcpy (self->s + self->len, s, n);
self->len += n;
return true;
}
inline static bool
ell_buffer_append_c (struct ell_buffer *self, char c) {
return ell_buffer_append (self, &c, 1);
}
// --- Values ------------------------------------------------------------------
enum ell_v_type { ELL_STRING, ELL_LIST };
struct ell_v {
enum ell_v_type type; ///< The type of this value
struct ell_v *next; ///< Next value in sequence
struct ell_v *head; ///< The head of the list
size_t len; ///< Length of "string" (sans '\0')
char string[]; ///< The null-terminated string value
};
static void ell_free_seq (struct ell_v *);
static struct ell_v *ell_clone_seq (const struct ell_v *);
static void
ell_free_v (struct ell_v *v) {
ell_free_seq (v->head);
free (v);
}
static void
ell_free_seq (struct ell_v *v) {
while (v) {
struct ell_v *link = v;
v = v->next;
ell_free_v (link);
}
}
static struct ell_v *
ell_clone (const struct ell_v *v) {
size_t size = sizeof *v + v->len + 1;
struct ell_v *clone = malloc (size);
if (!clone)
return NULL;
memcpy (clone, v, size);
if (clone->head && !(clone->head = ell_clone_seq (clone->head))) {
free (clone);
return NULL;
}
clone->next = NULL;
return clone;
}
static struct ell_v *
ell_clone_seq (const struct ell_v *v) {
struct ell_v *head = NULL;
for (struct ell_v **out = &head; v; v = v->next) {
if (!(*out = ell_clone (v))) {
ell_free_seq (head);
return NULL;
}
out = &(*out)->next;
}
return head;
}
static struct ell_v *
ell_string (const char *s, size_t len) {
struct ell_v *v = calloc (1, sizeof *v + len + 1);
if (!v)
return NULL;
v->type = ELL_STRING;
v->len = len;
memcpy (v->string, s, len);
return v;
}
static struct ell_v *
ell_list (struct ell_v *head) {
struct ell_v *v = calloc (1, sizeof *v + 1);
if (!v) {
ell_free_seq (head);
return NULL;
}
v->type = ELL_LIST;
v->head = head;
return v;
}
// --- Lexer -------------------------------------------------------------------
enum ell_token { ELLT_ABORT, ELLT_LPAREN, ELLT_RPAREN,
ELLT_LBRACKET, ELLT_RBRACKET, ELLT_LBRACE, ELLT_RBRACE,
ELLT_STRING, ELLT_NEWLINE, ELLT_AT };
static const char *ell_token_names[] = {
[ELLT_ABORT] = "end of input",
[ELLT_LPAREN] = "left parenthesis",
[ELLT_RPAREN] = "right parenthesis",
[ELLT_LBRACKET] = "left bracket",
[ELLT_RBRACKET] = "right bracket",
[ELLT_LBRACE] = "left brace",
[ELLT_RBRACE] = "right brace",
[ELLT_STRING] = "string",
[ELLT_NEWLINE] = "newline",
[ELLT_AT] = "at symbol",
};
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
struct ell_lexer {
const unsigned char *p; ///< Current position in input
size_t len; ///< How many bytes of input are left
unsigned line, column; ///< Current line and column
struct ell_buffer string; ///< Parsed string value
};
static struct ell_lexer
ell_lexer_make (const char *p, size_t len) {
return (struct ell_lexer) { .p = (const unsigned char *) p, .len = len };
}
static void
ell_lexer_free (struct ell_lexer *self) {
free (self->string.s);
}
static int
ell_lexer_advance (struct ell_lexer *self) {
int c = *self->p++;
if (c == '\n') {
self->column = 0;
self->line++;
} else
self->column++;
self->len--;
return c;
}
static bool
ell_lexer_hexa_escape (struct ell_lexer *self, struct ell_buffer *output) {
const char *abc = "0123456789abcdef", *h, *l;
if (!self->len || !(h = strchr (abc, tolower (ell_lexer_advance (self))))
|| !self->len || !(l = strchr (abc, tolower (ell_lexer_advance (self)))))
return false;
ell_buffer_append_c (output, (h - abc) << 4 | (l - abc));
return true;
}
enum {
ELL_LEXER_STRING_QUOTE = '\'',
ELL_LEXER_ESCAPE = '\\',
ELL_LEXER_COMMENT = '#'
};
static bool ell_lexer_is_whitespace (int c) {
return !c || c == ' ' || c == '\t' || c == '\r';
}
static unsigned char ell_lexer_escapes[256] = {
[ELL_LEXER_STRING_QUOTE] = ELL_LEXER_STRING_QUOTE,
[ELL_LEXER_ESCAPE] = ELL_LEXER_ESCAPE,
['a'] = '\a', ['b'] = '\b', ['n'] = '\n', ['r'] = '\r', ['t'] = '\t',
};
static const char *
ell_lexer_escape_sequence (struct ell_lexer *self, struct ell_buffer *output) {
if (!self->len)
return "premature end of escape sequence";
int c = ell_lexer_advance (self);
if (c == 'x') {
if (ell_lexer_hexa_escape (self, output))
return NULL;
return "invalid hexadecimal escape";
}
if (!(c = ell_lexer_escapes[c]))
return "unknown escape sequence";
ell_buffer_append_c (output, c);
return NULL;
}
static const char *
ell_lexer_string (struct ell_lexer *self, struct ell_buffer *output) {
int c;
const char *e = NULL;
while (self->len) {
if ((c = ell_lexer_advance (self)) == ELL_LEXER_STRING_QUOTE)
return NULL;
if (c != ELL_LEXER_ESCAPE)
ell_buffer_append_c (output, c);
else if ((e = ell_lexer_escape_sequence (self, output)))
return e;
}
return "premature end of string";
}
static enum ell_token ell_lexer_tokens[256] = {
['('] = ELLT_LPAREN, [')'] = ELLT_RPAREN,
['['] = ELLT_LBRACKET, [']'] = ELLT_RBRACKET,
['{'] = ELLT_LBRACE, ['}'] = ELLT_RBRACE,
[';'] = ELLT_NEWLINE, ['\n'] = ELLT_NEWLINE,
['@'] = ELLT_AT, [ELL_LEXER_STRING_QUOTE] = ELLT_STRING,
};
static enum ell_token
ell_lexer_next (struct ell_lexer *self, const char **e) {
while (self->len && ell_lexer_is_whitespace (*self->p))
ell_lexer_advance (self);
if (!self->len)
return ELLT_ABORT;
free (self->string.s);
self->string = ell_buffer_make ();
int c = ell_lexer_advance (self);
if (c == ELL_LEXER_COMMENT) {
while (self->len)
if (ell_lexer_advance (self) == '\n')
return ELLT_NEWLINE;
return ELLT_ABORT;
}
enum ell_token token = ell_lexer_tokens[c];
if (!token) {
ell_buffer_append_c (&self->string, c);
while (self->len && !ell_lexer_is_whitespace (*self->p)
&& !ell_lexer_tokens[*self->p])
ell_buffer_append_c (&self->string, ell_lexer_advance (self));
return ELLT_STRING;
}
if (token == ELLT_STRING
&& (*e = ell_lexer_string (self, &self->string)))
return ELLT_ABORT;
return token;
}
static char *ell_lexer_errorf (struct ell_lexer *self, const char *fmt, ...)
ELL_ATTRIBUTE_PRINTF (2, 3);
static char *
ell_lexer_errorf (struct ell_lexer *self, const char *fmt, ...) {
va_list ap;
va_start (ap, fmt);
char *description = ell_vformat (fmt, ap);
va_end (ap);
if (!description)
return NULL;
char *e = ell_format ("at or before line %u, column %u: %s",
self->line + 1, self->column + 1, description);
free (description);
return e;
}
// --- Printing ----------------------------------------------------------------
// This can be wrapped inside a larger structure, and errors simply accumulated
struct ell_printer {
void (*putchar) (struct ell_printer *self, unsigned char c);
};
static void ell_print_seq (struct ell_printer *printer, struct ell_v *v);
static bool
ell_print_string_needs_quoting (struct ell_v *s) {
for (size_t i = 0; i < s->len; i++) {
unsigned char c = s->string[i];
if (ell_lexer_is_whitespace (c) || ell_lexer_tokens[c]
|| c == ELL_LEXER_ESCAPE || c < 32)
return true;
}
return s->len == 0;
}
static bool
ell_print_string (struct ell_printer *printer, struct ell_v *s) {
if (s->type != ELL_STRING)
return false;
if (!ell_print_string_needs_quoting (s)) {
for (size_t i = 0; i < s->len; i++)
printer->putchar (printer, s->string[i]);
return true;
}
printer->putchar (printer, ELL_LEXER_STRING_QUOTE);
for (size_t i = 0; i < s->len; i++) {
unsigned char c = s->string[i];
if (c < 32) {
printer->putchar (printer, '\\');
printer->putchar (printer, 'x');
printer->putchar (printer, "0123456789abcdef"[c >> 4]);
printer->putchar (printer, "0123456789abcdef"[c & 15]);
} else if (c == ELL_LEXER_ESCAPE || c == ELL_LEXER_STRING_QUOTE) {
printer->putchar (printer, '\\');
printer->putchar (printer, c);
} else
printer->putchar (printer, c);
}
printer->putchar (printer, ELL_LEXER_STRING_QUOTE);
return true;
}
static bool
ell_print_block (struct ell_printer *printer, struct ell_v *list) {
if (!list->head || strcmp (list->head->string, "block"))
return false;
list = list->head->next;
for (struct ell_v *line = list; line; line = line->next)
if (line->type != ELL_LIST)
return false;
printer->putchar (printer, '{');
for (struct ell_v *line = list; line; line = line->next) {
printer->putchar (printer, ' ');
ell_print_seq (printer, line->head);
printer->putchar (printer, line->next ? ';' : ' ');
}
printer->putchar (printer, '}');
return true;
}
static bool
ell_print_set (struct ell_printer *printer, struct ell_v *list) {
if (!list->head || strcmp (list->head->string, "set")
|| !list->head->next || list->head->next->next)
return false;
printer->putchar (printer, '@');
ell_print_seq (printer, list->head->next);
return true;
}
static bool
ell_print_list (struct ell_printer *printer, struct ell_v *list) {
if (!list->head || strcmp (list->head->string, "list"))
return false;
printer->putchar (printer, '[');
ell_print_seq (printer, list->head->next);
printer->putchar (printer, ']');
return true;
}
static void
ell_print_v (struct ell_printer *printer, struct ell_v *v) {
if (ell_print_string (printer, v)
|| ell_print_block (printer, v)
|| ell_print_set (printer, v)
|| ell_print_list (printer, v))
return;
printer->putchar (printer, '(');
ell_print_seq (printer, v->head);
printer->putchar (printer, ')');
}
static void
ell_print_seq (struct ell_printer *printer, struct ell_v *v) {
for (; v; v = v->next) {
ell_print_v (printer, v);
if (v->next)
printer->putchar (printer, ' ');
}
}
// --- Parsing -----------------------------------------------------------------
struct ell_parser {
struct ell_lexer lexer; ///< Tokenizer
char *error; ///< Tokenizer error
enum ell_token token; ///< Current token in the lexer
bool replace_token; ///< Replace the token
bool memory_failure; ///< Memory allocation failed
};
static struct ell_parser
ell_parser_make (const char *script, size_t len) {
// As reading in tokens may cause exceptions, we wait for the first peek()
// to replace the initial ELLT_ABORT.
return (struct ell_parser) {
.lexer = ell_lexer_make (script, len),
.replace_token = true,
};
}
static void
ell_parser_free (struct ell_parser *p) {
ell_lexer_free (&p->lexer);
if (p->error)
free (p->error);
}
static enum ell_token
ell_parser_peek (struct ell_parser *p, jmp_buf out) {
if (p->replace_token) {
const char *e = NULL;
p->token = ell_lexer_next (&p->lexer, &e);
if (e) {
p->memory_failure =
!(p->error = ell_lexer_errorf (&p->lexer, "%s", e));
longjmp (out, 1);
}
if (p->token == ELLT_STRING && p->lexer.string.memory_failure)
longjmp (out, 1);
p->replace_token = false;
}
return p->token;
}
static bool
ell_parser_accept (struct ell_parser *p, enum ell_token token, jmp_buf out) {
return p->replace_token = (ell_parser_peek (p, out) == token);
}
static void
ell_parser_expect (struct ell_parser *p, enum ell_token token, jmp_buf out) {
if (ell_parser_accept (p, token, out))
return;
p->memory_failure = !(p->error = ell_lexer_errorf (&p->lexer,
"unexpected `%s', expected `%s'",
ell_token_names[p->token], ell_token_names[token]));
longjmp (out, 1);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// We don't need no generator, but a few macros will come in handy.
// From time to time C just doesn't have the right features.
#define PEEK() ell_parser_peek (p, err)
#define ACCEPT(token) ell_parser_accept (p, token, err)
#define EXPECT(token) ell_parser_expect (p, token, err)
#define SKIP_NL() do {} while (ACCEPT (ELLT_NEWLINE))
static struct ell_v *
ell_parser_check (struct ell_parser *p, struct ell_v *v, jmp_buf out) {
if (!v) {
p->memory_failure = true;
longjmp (out, 1);
}
return v;
}
// Beware that this jumps to the "out" buffer directly
#define CHECK(v) ell_parser_check (p, (v), out)
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static struct ell_v *
ell_parse_prefix_list (struct ell_v *seq, const char *name) {
struct ell_v *prefix;
if (!(prefix = ell_string (name, strlen (name)))) {
ell_free_seq (seq);
return NULL;
}
prefix->next = seq;
return ell_list (prefix);
}
static struct ell_v * ell_parse_line (struct ell_parser *p, jmp_buf out);
static struct ell_v *
ell_parse_v (struct ell_parser *p, jmp_buf out) {
jmp_buf err;
struct ell_v *volatile result = NULL, *volatile *tail = &result;
if (setjmp (err)) {
ell_free_seq (result);
longjmp (out, 1);
}
SKIP_NL ();
if (ACCEPT (ELLT_STRING))
return CHECK (ell_string
(p->lexer.string.s, p->lexer.string.len));
if (ACCEPT (ELLT_AT)) {
result = ell_parse_v (p, out);
return CHECK (ell_parse_prefix_list (result, "set"));
}
if (ACCEPT (ELLT_LPAREN)) {
while (!ACCEPT (ELLT_RPAREN)) {
tail = &(*tail = ell_parse_v (p, err))->next;
SKIP_NL ();
}
return CHECK (ell_list (result));
}
if (ACCEPT (ELLT_LBRACKET)) {
while (!ACCEPT (ELLT_RBRACKET)) {
tail = &(*tail = ell_parse_v (p, err))->next;
SKIP_NL ();
}
return CHECK (ell_parse_prefix_list (result, "list"));
}
if (ACCEPT (ELLT_LBRACE)) {
while ((*tail = ell_parse_line (p, err)))
tail = &(*tail)->next;
EXPECT (ELLT_RBRACE);
return CHECK (ell_parse_prefix_list (result, "block"));
}
p->memory_failure = !(p->error = ell_lexer_errorf (&p->lexer,
"unexpected `%s', expected a value", ell_token_names[p->token]));
longjmp (out, 1);
}
static struct ell_v *
ell_parse_line (struct ell_parser *p, jmp_buf out) {
jmp_buf err;
struct ell_v *volatile result = NULL, *volatile *tail = &result;
if (setjmp (err)) {
ell_free_seq (result);
longjmp (out, 1);
}
while (PEEK () != ELLT_RBRACE && PEEK () != ELLT_ABORT) {
if (!ACCEPT (ELLT_NEWLINE)) {
tail = &(*tail = ell_parse_v (p, err))->next;
} else if (result) {
return CHECK (ell_list (result));
}
}
if (result)
return CHECK (ell_list (result));
return NULL;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
#undef PEEK
#undef ACCEPT
#undef EXPECT
#undef SKIP_NL
#undef CHECK
static struct ell_v *
ell_parser_run (struct ell_parser *p, const char **e) {
jmp_buf err;
struct ell_v *volatile result = NULL, *volatile *tail = &result;
if (setjmp (err)) {
ell_free_seq (result);
*e = p->error;
if (p->memory_failure || p->lexer.string.memory_failure)
*e = "memory allocation failure";
return NULL;
}
while ((*tail = ell_parse_line (p, err)))
tail = &(*tail)->next;
ell_parser_expect (p, ELLT_ABORT, err);
return result;
}
// --- Runtime -----------------------------------------------------------------
struct ell {
struct ell_v *globals; ///< List of global variables
struct ell_v *scopes; ///< Dynamic scopes from newest
struct ell_native_fn *native; ///< Maps strings to C functions
char *error; ///< Error information
bool memory_failure; ///< Memory allocation failure
void *user_data; ///< User data
};
typedef bool (*EllHandler) (struct ell *, struct ell_v *, struct ell_v **);
struct ell_native_fn {
struct ell_native_fn *next; ///< The next link in the chain
EllHandler handler; ///< Internal C handler, or NULL
char name[]; ///< The name of the function
};
static struct ell ell_make (void) { return (struct ell) {}; }
static void
ell_free (struct ell *ell) {
struct ell_native_fn *next, *iter;
for (iter = ell->native; iter; iter = next) {
next = iter->next;
free (iter);
}
ell_free_seq (ell->globals);
ell_free_seq (ell->scopes);
free (ell->error);
}
static bool
ell_check (struct ell *ell, struct ell_v *v) {
return !(ell->memory_failure |= !v);
}
static struct ell_v **
ell_scope_find (struct ell_v **scope, const char *name) {
for (; *scope; scope = &(*scope)->next)
if (!strcmp ((*scope)->head->string, name))
return scope;
return NULL;
}
static bool
ell_scope_prepend (struct ell *ell, struct ell_v **scope, const char *name,
struct ell_v *v) {
struct ell_v *key, *pair;
if (!ell_check (ell, (key = ell_string (name, strlen (name))))
|| !ell_check (ell, (pair = ell_list (key)))) {
ell_free_seq (v);
return false;
}
key->next = v;
pair->next = *scope;
*scope = pair;
return true;
}
static struct ell_v *
ell_get (struct ell *ell, const char *name) {
struct ell_v **place;
for (struct ell_v *scope = ell->scopes; scope; scope = scope->next)
if ((place = ell_scope_find (&scope->head, name)))
return (*place)->head->next;
if (!(place = ell_scope_find (&ell->globals, name)))
return NULL;
return (*place)->head->next;
}
static bool
ell_set (struct ell *ell, const char *name, struct ell_v *v) {
struct ell_v **place;
for (struct ell_v *scope = ell->scopes; scope; scope = scope->next) {
if ((place = ell_scope_find (&scope->head, name))) {
ell_free_seq ((*place)->head->next);
(*place)->head->next = v;
return true;
}
}
// Variables only get deleted by "arg" or from the global scope
if ((place = ell_scope_find (&ell->globals, name))) {
struct ell_v *tmp = *place;
*place = (*place)->next;
ell_free_v (tmp);
}
return !v || ell_scope_prepend (ell, &ell->globals, name, v);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static struct ell_native_fn *
ell_native_find (struct ell *ell, const char *name) {
for (struct ell_native_fn *fn = ell->native; fn; fn = fn->next)
if (!strcmp (fn->name, name))
return fn;
return NULL;
}
static bool
ell_native_register (struct ell *ell, const char *name, EllHandler handler) {
struct ell_native_fn *fn = ell_native_find (ell, name);
if (!fn) {
if (!(fn = calloc (1, sizeof *fn + strlen (name) + 1)))
return false;
strcpy (fn->name, name);
fn->next = ell->native;
ell->native = fn;
}
fn->handler = handler;
return true;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static bool
ell_error (struct ell *ell, const char *ell_format, ...) {
va_list ap;
va_start (ap, ell_format);
free (ell->error);
if (!(ell->error = ell_vformat (ell_format, ap)))
ell->memory_failure = true;
va_end (ap);
return false;
}
static bool
ell_can_modify_error (struct ell *ell) {
// In that case, `error' is NULL and there's nothing else to do anyway.
// Errors starting with an underscore are exceptions and would not work
// with stack traces generated this way.
return !ell->memory_failure && ell->error[0] != '_';
}
static bool ell_eval_statement
(struct ell *, const struct ell_v *, struct ell_v **);
static bool ell_eval_block
(struct ell *, const struct ell_v *, struct ell_v *, struct ell_v **);
static bool
ell_eval_args (struct ell *ell,
const struct ell_v *args, struct ell_v **result) {
size_t i = 0;
struct ell_v *res = NULL, **out = &res;
for (; args; args = args->next) {
struct ell_v *evaluated = NULL;
// Arguments should not evaporate, default to a nil value
if (!ell_eval_statement (ell, args, &evaluated)
|| (!evaluated && !ell_check (ell, (evaluated = ell_list (NULL)))))
goto error;
ell_free_seq (evaluated->next);
evaluated->next = NULL;
out = &(*out = evaluated)->next;
i++;
}
*result = res;
return true;
error:
// Once the code flows like this, at least make some use of it
if (ell_can_modify_error (ell)) {
char *tmp = ell->error;
ell->error = NULL;
ell_error (ell, "(argument %zu) -> %s", i, tmp);
free (tmp);
}
ell_free_seq (res);
return false;
}
static bool
ell_eval_native (struct ell *ell, const char *name, const struct ell_v *args,
struct ell_v **result) {
struct ell_native_fn *fn = ell_native_find (ell, name);
if (!fn)
return ell_error (ell, "unknown function");
struct ell_v *arguments = NULL;
if (!ell_eval_args (ell, args, &arguments))
return false;
bool ok = fn->handler (ell, arguments, result);
ell_free_seq (arguments);
return ok;
}
static bool
ell_eval_resolved (struct ell *ell,
const struct ell_v *body, const struct ell_v *args, struct ell_v **result) {
// Resolving names recursively could be pretty fatal, let's not do that
if (body->type == ELL_STRING)
return ell_check (ell, (*result = ell_clone (body)));
struct ell_v *arguments = NULL;
return ell_eval_args (ell, args, &arguments)
&& ell_eval_block (ell, body->head, arguments, result);
}
static bool
ell_eval_value (struct ell *ell, const struct ell_v *body,
struct ell_v **result) {
const struct ell_v *args = body->next;
if (body->type == ELL_STRING) {
const char *name = body->string;
if (!strcmp (name, "block")) {
struct ell_v *cloned = NULL;
return (!args || ell_check (ell, (cloned = ell_clone_seq (args))))
&& ell_check (ell, (*result = ell_list (cloned)));
}
if ((body = ell_get (ell, name)))
return ell_eval_resolved (ell, body, args, result);
return ell_eval_native (ell, name, args, result);
}
// When someone tries to call a block directly, we must evaluate it;
// e.g. something like `{ choose [@f1 @f2 @f3] } arg1 arg2 arg3`.
struct ell_v *evaluated = NULL;
if (!ell_eval_statement (ell, body, &evaluated))
return false;
// It might a bit confusing that this doesn't evaluate arguments
// but neither does "block" and there's nothing to do here
if (!evaluated)
return true;
bool ok = ell_eval_resolved (ell, evaluated, args, result);
ell_free_seq (evaluated);
return ok;
}
static bool
ell_eval_statement
(struct ell *ell, const struct ell_v *statement, struct ell_v **result) {
if (statement->type == ELL_STRING)
return ell_check (ell, (*result = ell_clone (statement)));
// Executing a nil value results in no value. It's not very different from
// calling a block that returns no value--it's for our callers to resolve.
if (!statement->head
|| ell_eval_value (ell, statement->head, result))
return true;
ell_free_seq (*result);
*result = NULL;
const char *name = "(block)";
if (statement->head->type == ELL_STRING)
name = statement->head->string;
if (ell_can_modify_error (ell)) {
char *tmp = ell->error;
ell->error = NULL;
ell_error (ell, "%s -> %s", name, tmp);
free (tmp);
}
return false;
}
static bool
args_to_scope (struct ell *ell, struct ell_v *args, struct ell_v **scope) {
if (!ell_check (ell, (args = ell_list (args)))
|| !ell_scope_prepend (ell, scope, "args", args))
return false;
size_t i = 0;
for (args = args->head; args; args = args->next) {
char buf[16] = "";
(void) snprintf (buf, sizeof buf, "%zu", ++i);
struct ell_v *copy = NULL;
if ((args && !ell_check (ell, (copy = ell_clone (args))))
|| !ell_scope_prepend (ell, scope, buf, copy))
return false;
}
return ell_check (ell, (*scope = ell_list (*scope)));
}
/// Execute a block and return whatever the last statement returned, eats args
static bool
ell_eval_block (struct ell *ell, const struct ell_v *body, struct ell_v *args,
struct ell_v **result) {
struct ell_v *scope = NULL;
if (!args_to_scope (ell, args, &scope)) {
ell_free_seq (scope);
return false;
}
scope->next = ell->scopes;
ell->scopes = scope;
bool ok = true;
for (; body; body = body->next) {
ell_free_seq (*result);
*result = NULL;
if (!(ok = ell_eval_statement (ell, body, result)))
break;
}
ell->scopes = scope->next;
ell_free_v (scope);
return ok;
}
// --- Standard library --------------------------------------------------------
#define ell_defn(name) static bool name \
(struct ell *ell, struct ell_v *args, struct ell_v **result)
static bool
ell_eval_any (struct ell *ell,
const struct ell_v *body, const struct ell_v *arg, struct ell_v **result) {
if (body->type == ELL_STRING)
return ell_check (ell, (*result = ell_clone (body)));
struct ell_v *cloned_arg = NULL;
if (arg && !ell_check (ell, (cloned_arg = ell_clone (arg))))
return false;
return ell_eval_block (ell, body->head, cloned_arg, result);
}
static struct ell_v *
ell_number (double n) {
char *s;
if (!(s = ell_format ("%f", n)))
return NULL;
char *p = strchr (s, 0);
while (--p > s && *p == '0')
*p = 0;
if (*p == '.')
*p = 0;
struct ell_v *v = ell_string (s, strlen (s));
free (s);
return v;
}
static bool ell_truthy (struct ell_v *v) { return v && (v->head || v->len); }
static struct ell_v *ell_boolean (bool b) { return ell_string ("1", b); }
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static void
ell_stdout_printer_putchar (struct ell_printer *self, unsigned char c) {
(void) self;
(void) putchar (c);
}
static struct ell_printer ell_stdout_printer = { ell_stdout_printer_putchar };
struct ell_buffer_printer {
struct ell_printer super; ///< Superclass
struct ell_buffer *output; ///< Where to append the result to
};
static void
ell_buffer_printer_putchar (struct ell_printer *printer, unsigned char c) {
struct ell_buffer_printer *self = (struct ell_buffer_printer *) printer;
ell_buffer_append_c (self->output, c);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
ell_defn (ell_fn_local) {
struct ell_v *names = args;
if (!names || names->type != ELL_LIST)
return ell_error (ell, "first argument must be a list");
// Duplicates or non-strings don't really matter to us, user's problem
struct ell_v **scope = &ell->scopes->head;
(void) result;
struct ell_v *values = names->next;
for (names = names->head; names; names = names->next) {
struct ell_v *value = NULL;
if ((values && !ell_check (ell, (value = ell_clone (values))))
|| !ell_scope_prepend (ell, scope, names->string, value))
return false;
if (values)
values = values->next;
}
return true;
}
ell_defn (ell_fn_set) {
struct ell_v *name = args;
if (!name || name->type != ELL_STRING)
return ell_error (ell, "first argument must be string");
struct ell_v *v;
if ((v = name->next))
return ell_check (ell, (v = ell_clone (v)))
&& ell_check (ell, (*result = ell_clone (v)))
&& ell_set (ell, name->string, v);
// We return an empty list for a nil value
if (!(v = ell_get (ell, name->string)))
return ell_check (ell, (*result = ell_list (NULL)));
return ell_check (ell, (*result = ell_clone (v)));
}
ell_defn (ell_fn_list) {
struct ell_v *values = NULL;
if (args && !ell_check (ell, (values = ell_clone_seq (args))))
return false;
return ell_check (ell, (*result = ell_list (values)));
}
ell_defn (ell_fn_values) {
return !args || ell_check (ell, (*result = ell_clone_seq (args)));
}
ell_defn (ell_fn_if) {
struct ell_v *cond, *body, *keyword;
for (cond = args; ; cond = keyword->next) {
if (!cond)
return ell_error (ell, "missing condition");
if (!(body = cond->next))
return ell_error (ell, "missing body");
struct ell_v *res = NULL;
if (!ell_eval_any (ell, cond, NULL, &res))
return false;
bool match = ell_truthy (res);
ell_free_seq (res);
if (match)
return ell_eval_any (ell, body, NULL, result);
if (!(keyword = body->next))
break;
if (keyword->type != ELL_STRING)
return ell_error (ell, "expected keyword, got list");
if (!strcmp (keyword->string, "else")) {
if (!(body = keyword->next))
return ell_error (ell, "missing body");
return ell_eval_any (ell, body, NULL, result);
}
if (strcmp (keyword->string, "elif"))
return ell_error (ell, "invalid keyword: %s", keyword->string);
}
return true;
}
ell_defn (ell_fn_map) {
struct ell_v *body, *values;
if (!(body = args))
return ell_error (ell, "first argument must be a function");
if (!(values = body->next) || values->type != ELL_LIST)
return ell_error (ell, "second argument must be a list");
struct ell_v *res = NULL, **out = &res;
for (struct ell_v *v = values->head; v; v = v->next) {
if (!ell_eval_any (ell, body, v, out)) {
ell_free_seq (res);
return false;
}
while (*out)
out = &(*out)->next;
}
return ell_check (ell, (*result = ell_list (res)));
}
ell_defn (ell_fn_print) {
(void) result;
for (; args; args = args->next) {
if (args->type != ELL_STRING)
ell_print_v (&ell_stdout_printer, args);
else if (fwrite (args->string, 1, args->len, stdout) != args->len)
return ell_error (ell, "write failed: %s", strerror (errno));
}
return true;
}
ell_defn (ell_fn_cat) {
struct ell_buffer buf = ell_buffer_make ();
struct ell_buffer_printer bp = { { ell_buffer_printer_putchar }, &buf };
for (; args; args = args->next) {
if (args->type != ELL_STRING)
ell_print_v (&bp.super, args);
else
ell_buffer_append (&buf, args->string, args->len);
}
bool ok = !(ell->memory_failure |= buf.memory_failure)
&& ell_check (ell, (*result = ell_string (buf.s, buf.len)));
free (buf.s);
return ok;
}
ell_defn (ell_fn_system) {
struct ell_v *command = args;
if (!command || command->type != ELL_STRING)
return ell_error (ell, "first argument must be string");
if (command->next)
return ell_error (ell, "cannot deal with multiple arguments");
return ell_check (ell, (*result = ell_number (system (command->string))));
}
ell_defn (ell_fn_parse) {
struct ell_v *body = args;
if (!body || body->type != ELL_STRING)
return ell_error (ell, "first argument must be string");
struct ell_parser p = ell_parser_make (args->string, args->len);
const char *e = NULL;
bool ok = ell_check (ell, (*result = ell_list (ell_parser_run (&p, &e))));
if (e)
ok = ell_error (ell, "%s", e);
ell_parser_free (&p);
return ok;
}
ell_defn (ell_fn_try) {
struct ell_v *body, *handler;
if (!(body = args))
return ell_error (ell, "first argument must be a function");
if (!(handler = body->next))
return ell_error (ell, "second argument must be a function");
if (ell_eval_any (ell, body, NULL, result))
return true;
struct ell_v *msg;
if (ell->memory_failure
|| !ell_check (ell, (msg = ell_string (ell->error, strlen (ell->error)))))
return false;
free (ell->error); ell->error = NULL;
ell_free_seq (*result); *result = NULL;
bool ok = ell_eval_any (ell, handler, msg, result);
ell_free_v (msg);
return ok;
}
ell_defn (ell_fn_throw) {
(void) result;
struct ell_v *message = args;
if (!message || message->type != ELL_STRING)
return ell_error (ell, "first argument must be string");
return ell_error (ell, "%s", message->string);
}
ell_defn (ell_fn_plus) {
double res = 0.0;
for (; args; args = args->next) {
if (args->type != ELL_STRING)
return ell_error (ell, "arguments must be strings");
res += strtod (args->string, NULL);
}
return ell_check (ell, (*result = ell_number (res)));
}
ell_defn (ell_fn_minus) {
if (!args || args->type != ELL_STRING)
return ell_error (ell, "first argument must be string");
double res = strtod (args->string, NULL);
if (!(args = args->next))
res = -res;
for (; args; args = args->next) {
if (args->type != ELL_STRING)
return ell_error (ell, "arguments must be strings");
res -= strtod (args->string, NULL);
}
return ell_check (ell, (*result = ell_number (res)));
}
ell_defn (ell_fn_multiply) {
double res = 1.0;
for (; args; args = args->next) {
if (args->type != ELL_STRING)
return ell_error (ell, "arguments must be strings");
res *= strtod (args->string, NULL);
}
return ell_check (ell, (*result = ell_number (res)));
}
ell_defn (ell_fn_divide) {
if (!args || args->type != ELL_STRING)
return ell_error (ell, "first argument must be string");
double res = strtod (args->string, NULL), x;
for (args = args->next; args; args = args->next) {
if (args->type != ELL_STRING)
return ell_error (ell, "arguments must be strings");
if (!(x = strtod (args->string, NULL)))
return ell_error (ell, "division by zero");
res /= x;
}
return ell_check (ell, (*result = ell_number (res)));
}
ell_defn (ell_fn_not) {
if (!args)
return ell_error (ell, "missing argument");
return ell_check (ell, (*result = ell_boolean (!ell_truthy (args))));
}
ell_defn (ell_fn_and) {
if (!args)
return ell_check (ell, (*result = ell_boolean (true)));
for (; args; args = args->next) {
ell_free_seq (*result);
*result = NULL;
if (!ell_eval_any (ell, args, NULL, result))
return false;
if (!ell_truthy (*result))
return ell_check (ell, (*result = ell_boolean (false)));
}
return true;
}
ell_defn (ell_fn_or) {
for (; args; args = args->next) {
if (!ell_eval_any (ell, args, NULL, result))
return false;
if (ell_truthy (*result))
return true;
ell_free_seq (*result);
*result = NULL;
}
return ell_check (ell, (*result = ell_boolean (false)));
}
ell_defn (ell_fn_eq) {
struct ell_v *etalon = args;
if (!etalon || etalon->type != ELL_STRING)
return ell_error (ell, "first argument must be string");
bool res = true;
for (args = etalon->next; args; args = args->next) {
if (args->type != ELL_STRING)
return ell_error (ell, "arguments must be strings");
if (!(res &= !strcmp (etalon->string, args->string)))
break;
}
return ell_check (ell, (*result = ell_boolean (res)));
}
ell_defn (ell_fn_lt) {
struct ell_v *etalon = args;
if (!etalon || etalon->type != ELL_STRING)
return ell_error (ell, "first argument must be string");
bool res = true;
for (args = etalon->next; args; args = args->next) {
if (args->type != ELL_STRING)
return ell_error (ell, "arguments must be strings");
if (!(res &= strcmp (etalon->string, args->string) < 0))
break;
etalon = args;
}
return ell_check (ell, (*result = ell_boolean (res)));
}
ell_defn (ell_fn_equals) {
struct ell_v *etalon = args;
if (!etalon || etalon->type != ELL_STRING)
return ell_error (ell, "first argument must be string");
bool res = true;
for (args = etalon->next; args; args = args->next) {
if (args->type != ELL_STRING)
return ell_error (ell, "arguments must be strings");
if (!(res &= strtod (etalon->string, NULL)
== strtod (args->string, NULL)))
break;
}
return ell_check (ell, (*result = ell_boolean (res)));
}
ell_defn (ell_fn_less) {
struct ell_v *etalon = args;
if (!etalon || etalon->type != ELL_STRING)
return ell_error (ell, "first argument must be string");
bool res = true;
for (args = etalon->next; args; args = args->next) {
if (args->type != ELL_STRING)
return ell_error (ell, "arguments must be strings");
if (!(res &= strtod (etalon->string, NULL)
< strtod (args->string, NULL)))
break;
etalon = args;
}
return ell_check (ell, (*result = ell_boolean (res)));
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static struct ell_handler_pair {
const char *name; ///< Name of function
EllHandler handler; ///< Handler for the function
} ell_std_native[] = {
{ "local", ell_fn_local },
{ "set", ell_fn_set },
{ "list", ell_fn_list },
{ "values", ell_fn_values },
{ "if", ell_fn_if },
{ "map", ell_fn_map },
{ "print", ell_fn_print },
{ "..", ell_fn_cat },
{ "system", ell_fn_system },
{ "parse", ell_fn_parse },
{ "try", ell_fn_try },
{ "throw", ell_fn_throw },
{ "+", ell_fn_plus },
{ "-", ell_fn_minus },
{ "*", ell_fn_multiply },
{ "/", ell_fn_divide },
{ "not", ell_fn_not },
{ "and", ell_fn_and },
{ "or", ell_fn_or },
{ "eq?", ell_fn_eq },
{ "lt?", ell_fn_lt },
{ "=", ell_fn_equals },
{ "<", ell_fn_less },
};
const char ell_std_composed[] =
"set unless { if (not (@1)) @2 }\n"
"set filter { local [_body _list] @1 @2;"
" map { if (@_body @1) { @1 } } @_list }\n"
"set for { local [_list _body] @1 @2;"
" try { map { @_body @1 } @_list } { if (ne? @1 _break) { throw @1 } } }\n"
"set break { throw _break }\n"
// TODO: we should be able to apply them to all arguments
"set ne? { not (eq? @1 @2) }; set le? { ge? @2 @1 }\n"
"set ge? { not (lt? @1 @2) }; set gt? { lt? @2 @1 }\n"
"set <> { not (= @1 @2) }; set <= { >= @2 @1 }\n"
"set >= { not (< @1 @2) }; set > { < @2 @1 }\n";
static bool
ell_std_initialize (struct ell *ell) {
for (size_t i = 0; i < ELL_N_ELEMENTS (ell_std_native); i++) {
struct ell_handler_pair *pair = &ell_std_native[i];
if (!ell_native_register (ell, pair->name, pair->handler))
return false;
}
struct ell_parser p =
ell_parser_make (ell_std_composed, sizeof ell_std_composed);
const char *e = NULL;
struct ell_v *result = NULL;
struct ell_v *program = ell_parser_run (&p, &e);
bool ok = !e && ell_eval_block (ell, program, NULL, &result);
ell_parser_free (&p);
ell_free_seq (program);
ell_free_seq (result);
return ok;
}
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