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Can handle parentheses in expressions.

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This commit is contained in:
Lawrence Kesteloot 2018-08-03 18:38:55 -07:00
parent 61f85e228c
commit d7830c49af
1 changed files with 41 additions and 4 deletions
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45
main.c
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@ -69,6 +69,8 @@ uint8_t title_length = 9;
#define OP_DIV 0xCB
#define OP_NEG 0xDD
#define OP_EXP 0xEE
#define OP_CLOSE_PARENS 0xFD // Never on the stack.
#define OP_OPEN_PARENS 0xFE // Ignore precedence.
#define OP_INVALID 0xFF
// Line number used for "no line number".
@ -400,6 +402,14 @@ static void pop_operator_stack() {
case OP_GTE:
add_call(tosgeax);
break;
case OP_OPEN_PARENS:
// No-op.
break;
default:
print("Unhandled operator\n");
break;
}
}
@ -414,6 +424,7 @@ static void push_operator_stack(uint8_t op) {
// All our operators are left-associative, so no special check for the case
// of equal precedence.
while (g_op_stack_size > 0 &&
g_op_stack[g_op_stack_size - 1] != OP_OPEN_PARENS &&
OP_PRECEDENCE(g_op_stack[g_op_stack_size - 1]) >= OP_PRECEDENCE(op)) {
pop_operator_stack();
@ -505,20 +516,46 @@ static uint8_t *compile_expression(uint8_t *s) {
} else {
op = OP_GT;
}
} else if (*s == '(') { // Parentheses are not tokenized.
op = OP_OPEN_PARENS;
} else if (*s == ')') { // Parentheses are not tokenized.
op = OP_CLOSE_PARENS;
// Pop until open parethesis.
while (g_op_stack_size > 0 && g_op_stack[g_op_stack_size - 1] != OP_OPEN_PARENS) {
pop_operator_stack();
}
if (g_op_stack_size == 0) {
print("Extra close parenthesis\n");
} else {
// Pop open parenthesis.
pop_operator_stack();
}
}
if (op != OP_INVALID) {
s += 1;
push_operator_stack(op);
if (op != OP_CLOSE_PARENS) {
push_operator_stack(op);
}
} else {
break;
}
}
}
// Empty the operator stack.
while (g_op_stack_size > 0) {
pop_operator_stack();
if (have_value_in_ax) {
// Empty the operator stack.
while (g_op_stack_size > 0) {
if (g_op_stack[g_op_stack_size - 1] == OP_OPEN_PARENS) {
print("Extra open parenthesis\n");
}
pop_operator_stack();
}
} else {
// Something went wrong, we never got anything.
print("Expression has no content\n");
compile_load_ax(0);
}
return s;