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Add unary minus (negative).

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This commit is contained in:
Lawrence Kesteloot 2018-08-05 16:43:50 -07:00
parent fb323943ce
commit 84d9a7ce82
4 changed files with 22 additions and 5 deletions
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4
README.md
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@ -9,8 +9,8 @@ line numbers, 16-bit integer variables, `HOME`, `PRINT`, `IF/THEN`,
`FOR/NEXT`, `GOTO`, low-res graphics (`GR`, `PLOT`, `COLOR=`, `TEXT`),
`POKE`, and integer and boolean arithmetic.
Not supported: Floating point, strings, negative
integers, high-res graphics, `DATA/READ/RESUME`, `GOSUB/RETURN/POP`,
Not supported: Floating point, strings,
high-res graphics, `DATA/READ/RESUME`, `GOSUB/RETURN/POP`,
`DIM` (arrays), `REM`, keyboard input, exponentiation (`A^B`), and cassette I/O.
# Dependencies

1
exporter.h
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@ -16,6 +16,7 @@ extern void tosgtax();
extern void tosleax();
extern void tosgeax();
extern void bnegax();
extern void negax();
// Two bytes each.
extern unsigned int ptr1;

2
exporter.s
View File

@ -31,6 +31,8 @@
.export _tosgeax := tosgeax
.import bnegax
.export _bnegax := bnegax
.import negax
.export _negax := negax
.importzp ptr1
.exportzp _ptr1 = ptr1

20
main.c
View File

@ -516,6 +516,10 @@ static void pop_operator_stack() {
add_call(bnegax);
break;
case OP_NEG:
add_call(negax);
break;
case OP_OPEN_PARENS:
// No-op.
break;
@ -535,7 +539,7 @@ static void pop_operator_stack() {
*/
static void push_operator_stack(uint8_t op) {
// Don't pop anything off if op is unary.
if (op != OP_NOT) {
if (op != OP_NOT && op != OP_NEG) {
// All our operators are left-associative, so no special check for the case
// of equal precedence.
while (g_op_stack_size > 0 &&
@ -556,6 +560,7 @@ static void push_operator_stack(uint8_t op) {
*/
static uint8_t *compile_expression(uint8_t *s) {
char have_value_in_ax = 0;
uint8_t expect_unary_minus = 1; // Expect unary minus at start of expression.
while (1) {
if (IS_DIGIT(*s)) {
@ -567,6 +572,9 @@ static uint8_t *compile_expression(uint8_t *s) {
compile_load_ax(parse_uint16(&s));
have_value_in_ax = 1;
// Expect binary minus after operand.
expect_unary_minus = 0;
} else if (IS_FIRST_VARIABLE_LETTER(*s)) {
// Variable reference.
uint8_t var = find_variable(&s);
@ -590,6 +598,9 @@ static uint8_t *compile_expression(uint8_t *s) {
g_c += 4;
}
have_value_in_ax = 1;
// Expect binary minus after operand.
expect_unary_minus = 0;
} else {
// Check if it's an operator.
uint8_t op = OP_INVALID;
@ -597,8 +608,7 @@ static uint8_t *compile_expression(uint8_t *s) {
if (*s == T_PLUS) {
op = OP_ADD;
} else if (*s == T_MINUS) {
// TODO check for unary.
op = OP_SUB;
op = expect_unary_minus ? OP_NEG : OP_SUB;
} else if (*s == T_ASTERISK) {
op = OP_MULT;
} else if (*s == T_SLASH) {
@ -656,6 +666,10 @@ static uint8_t *compile_expression(uint8_t *s) {
}
}
// Expect unary minus after operators or open parenthesis. Expect
// binary minus after close parenthesis.
expect_unary_minus = op != OP_CLOSE_PARENS;
if (op != OP_INVALID) {
s += 1;
if (op != OP_CLOSE_PARENS) {