Forp: Rewrite if/else/then in Forth

This commit is contained in:
Jeremy Penner 2019-02-01 19:05:02 -05:00
parent c0f19f7674
commit 769bb9e9aa
2 changed files with 98 additions and 47 deletions

145
forp.c
View file

@ -44,6 +44,18 @@ void PUSHS(char *s) { stack->s = s; stack++; }
void RPUSH(cell c) { *rstack = c; rstack++; }
#define RPOP() (--rstack)
void f_here() {
PUSHCP(HERE);
}
void f_latest() {
PUSHCP(LATEST);
}
void f_state() {
PUSHC(STATE);
}
void f_add() {
cell r = TOP();
DROP(1);
@ -64,6 +76,7 @@ void f_set() {
cell *p = TOP().p;
DROP(1);
(*p) = TOP();
DROP(1);
}
void f_drop() {
@ -75,10 +88,10 @@ void f_dup() {
}
void f_swap() {
cell top = ST1();
cell st1 = TOP();
ST1() = st1;
TOP() = top;
cell top = TOP();
cell st1 = ST1();
TOP() = st1;
ST1() = top;
}
void f_rot() { // a b c -- b c a
@ -128,16 +141,24 @@ void f_emit() {
DROP(1);
}
void f_dot() {
printf("%d ", TOP().i);
void f_puts() {
char *s = TOP().s;
while (s && *s) {
PUSHI(*s);
f_emit();
s++;
}
DROP(1);
}
void f_puts() {
printf("%s", TOP().s);
DROP(1);
void f_dot() {
static char num[16];
sprintf(num, "%d ", TOP().i);
TOP().s = num;
f_puts();
}
void f_cr() {
PUSHI('\n');
f_emit();
@ -189,7 +210,7 @@ void f_docolon() {
void f_noop() {
}
void f_donumber() {
void f_push_() {
PUSHC(*IP.p);
IP.p++;
}
@ -225,6 +246,21 @@ void f_lookup() { // name -- (codepointer flags) | (name 0)
PUSHU(0);
}
void f_revlookup() { // codepointer -- name
cell *entry = LATEST;
while (entry) {
unsigned int length = entry[1].u & ~F_IMMEDIATE;
cell *name = entry + 2;
cell *cp = CELL_OFFSET(name, length + 1);
if (cp == TOP().p) {
TOP().p = name;
return;
}
entry = entry->p;
}
TOP().p = NULL;
}
void f_compileon() {
STATE.i = 1;
}
@ -236,12 +272,11 @@ void f_immediate() {
cell *flags = LATEST + 1;
flags->u |= F_IMMEDIATE;
}
void f_compileword();
void f_semicolon() {
PUSHS("_RET");
f_lookup();
DROP(1);
f_comma();
f_compileword();
f_compileoff();
}
@ -271,10 +306,8 @@ void f_interpretword() { // codefield flags --
void f_interpretnumber() { // number --
if (STATE.i) {
PUSHS("_DONUMBER");
f_lookup();
DROP(1);
f_comma();
PUSHS("PUSH_");
f_compileword();
f_comma();
}
}
@ -325,37 +358,34 @@ void f_interpret(char *input) {
}
void f_if() {
if (STATE.i) {
PUSHC(W);
f_comma();
PUSHP(HERE);
PUSHP(NULL);
f_comma();
PUSHS("IF_");
f_compileword();
PUSHP(HERE);
PUSHP(NULL);
f_comma();
}
void f_if_() {
if (TOP().u) {
IP.p ++;
} else {
if (TOP().u) {
IP.p ++;
} else {
IP.p = IP.p->p; // skip to then
}
DROP(1);
IP.p = IP.p->p; // skip to else or then
}
DROP(1);
}
void f_else() {
if (STATE.i) {
PUSHS("GOTO_");
f_compileword();
PUSHP(NULL);
f_comma();
PUSHC(W);
f_comma();
TOP().p->p = HERE; // make false condition of IF come here
TOP().p = HERE - 1; // make THEN patch our goto
}
TOP().p->p = HERE + 1;
TOP().p = HERE;
PUSHP(NULL);
f_comma();
} else {
IP.p = IP.p->p;
}
void f_goto_() {
IP.p = IP.p->p;
}
void f_then() {
@ -363,6 +393,17 @@ void f_then() {
DROP(1);
}
void f_quote() {
if (STATE.i) {
PUSHS("PUSH_");
f_compileword();
} else {
f_word();
f_lookup();
DROP(1);
}
}
int DIE = 0;
void f_quit() {
DIE = 1;
@ -372,31 +413,41 @@ void f_quit() {
void f_init() {
CDEF("[", f_compileoff); f_immediate();
CDEF("]", f_compileon);
CDEF("key", f_key);
CDEF("emit", f_emit);
CDEF("word", f_word);
CDEF("immediate", f_immediate);
CDEF("create", f_create);
CDEF("here", f_here);
CDEF("latest", f_latest);
CDEF("state", f_state);
CDEF("'", f_quote); f_immediate();
CDEF("`", f_revlookup);
CDEF(":", f_colon);
CDEF(";", f_semicolon); f_immediate();
CDEF("+", f_add);
CDEF("-", f_sub);
CDEF("@", f_get);
CDEF("!", f_set);
CDEF("if", f_if); f_immediate();
CDEF("else", f_else); f_immediate();
CDEF("then", f_then); f_immediate();
CDEF("dup", f_dup);
CDEF("drop", f_drop);
CDEF("swap", f_drop);
CDEF("swap", f_swap);
CDEF("rot", f_rot);
CDEF("emit", f_emit);
CDEF("number", f_number);
CDEF("_DONUMBER", f_donumber);
CDEF("PUSH_", f_push_);
CDEF("GOTO_", f_goto_);
CDEF("IF_", f_if_);
CDEF("_RET", f_ret);
CDEF(".", f_dot);
CDEF(".s", f_puts);
CDEF(",", f_comma);
CDEF("noop", f_noop);
CDEF("quit", f_quit);
f_interpret(": -rot rot rot ;");
f_interpret(": if ' IF_ , here 0 , ; immediate");
f_interpret(": else ' GOTO_ , 0 , here swap ! here 2 - ; immediate");
f_interpret(": then here swap ! ; immediate");
}
int main() {

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forp.exe

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