/* ParseFor - parse the 'FOR' statement */
static void ParseFor(ParseContext *c)
{
ParseTreeNode *var, *step;
int test, body, inst;
Token tkn;
PVAL pv;
PushBlock(c);
c->bptr->type = BLOCK_FOR;
/* get the control variable */
FRequire(c, T_IDENTIFIER);
var = GetSymbolRef(c, c->token);
code_lvalue(c, var, &pv);
FRequire(c, '=');
/* parse the starting value expression */
ParseRValue(c);
/* parse the TO expression and generate the loop termination test */
test = codeaddr(c);
(*pv.fcn)(c, PV_STORE, &pv);
(*pv.fcn)(c, PV_LOAD, &pv);
FRequire(c, T_TO);
ParseRValue(c);
putcbyte(c, OP_LE);
putcbyte(c, OP_BRT);
body = putcword(c, 0);
/* branch to the end if the termination test fails */
putcbyte(c, OP_BR);
c->bptr->u.ForBlock.end = putcword(c, 0);
/* update the for variable after an iteration of the loop */
c->bptr->u.ForBlock.nxt = codeaddr(c);
(*pv.fcn)(c, PV_LOAD, &pv);
/* get the STEP expression */
if ((tkn = GetToken(c)) == T_STEP) {
step = ParseExpr(c);
code_rvalue(c, step);
tkn = GetToken(c);
}
/* no step so default to one */
else {
putcbyte(c, OP_LIT);
putcword(c, 1);
}
/* generate the increment code */
putcbyte(c, OP_ADD);
inst = putcbyte(c, OP_BR);
putcword(c, test - inst - 1 - sizeof(VMUVALUE));
/* branch to the loop body */
fixupbranch(c, body, codeaddr(c));
Require(c, tkn, T_EOL);
}
/* ParseImpliedLetOrFunctionCall - parse an implied let statement or a function call */
static void ParseImpliedLetOrFunctionCall(ParseContext *c)
{
ParseTreeNode *expr;
Token tkn;
PVAL pv;
expr = ParsePrimary(c);
switch (tkn = GetToken(c)) {
case '=':
code_lvalue(c, expr, &pv);
ParseRValue(c);
(*pv.fcn)(c, PV_STORE, &pv);
break;
default:
SaveToken(c, tkn);
code_rvalue(c, expr);
putcbyte(c, OP_DROP);
break;
}
FRequire(c, T_EOL);
}
/* CallHandler - compile a call to a runtime print function */
static void CallHandler(ParseContext *c, char *name, ParseTreeNode *expr)
{
Symbol *sym;
/* find the built-in function */
if (!(sym = FindSymbol(&c->globals, name)))
ParseError(c, "undefined print function: %s", name);
/* compile the function symbol reference */
putcbyte(c, OP_LIT);
putcword(c, sym->value);
/* compile the argument */
if (expr)
code_rvalue(c, expr);
/* call the function */
putcbyte(c, OP_CALL);
putcbyte(c, (expr ? 1 : 0));
putcbyte(c, OP_DROP);
}
/* ParseRValue - parse and generate code for an r-value */
void ParseRValue(ParseContext *c)
{
ParseTreeNode *expr;
expr = ParseExpr(c);
code_rvalue(c, expr);
}
