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Add AND and OR.

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This commit is contained in:
Lawrence Kesteloot 2018-08-05 16:12:58 -07:00
parent e3739f92c2
commit 007cf3e670
2 changed files with 66 additions and 2 deletions
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2
README.md
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@ -9,7 +9,7 @@ line numbers, 16-bit integer variables, `HOME`, `PRINT`, `IF/THEN`,
`FOR/NEXT`, `GOTO`, low-res graphics (`GR`, `PLOT`, `COLOR=`, `TEXT`),
`POKE`, and basic arithmetic.
Not supported: Floating point, strings, `AND`, `OR`, `NOT`, negative
Not supported: Floating point, strings, `NOT`, negative
integers, high-res graphics, `DATA/READ/RESUME`, `GOSUB/RETURN/POP`,
`DIM` (arrays), `REM`, keyboard input, and cassette I/O.

66
main.c
View File

@ -450,6 +450,66 @@ static void pop_operator_stack() {
add_call(tosgeax);
break;
case OP_AND:
// AppleSoft BASIC does not have short-circuit logical operators.
// See if second operand is 0.
g_c[0] = I_STX_ZPG;
g_c[1] = (uint8_t) &tmp1;
g_c[2] = I_ORA_ZPG;
g_c[3] = (uint8_t) &tmp1;
// If so, skip other test. A contains 0.
g_c[4] = I_BEQ_REL;
g_c[5] = 11; // 3 + 6 + 2
g_c += 6;
add_call(popax); // 3 instructions
// See if first operand is 0.
g_c[0] = I_STX_ZPG;
g_c[1] = (uint8_t) &tmp1;
g_c[2] = I_ORA_ZPG;
g_c[3] = (uint8_t) &tmp1;
// If so, skip setting A to 1. A contains 0.
g_c[4] = I_BEQ_REL;
g_c[5] = 2; // The LDA below.
g_c += 6;
// Set A to 1.
g_c[0] = I_LDA_IMM;
g_c[1] = 1;
g_c[2] = I_LDX_IMM; // The BEQs above arrive here.
g_c[3] = 0;
g_c += 4;
break;
case OP_OR:
// AppleSoft BASIC does not have short-circuit logical operators.
// See if second operand is 0.
g_c[0] = I_STX_ZPG;
g_c[1] = (uint8_t) &tmp1;
g_c[2] = I_ORA_ZPG;
g_c[3] = (uint8_t) &tmp1;
// If not, skip other test.
g_c[4] = I_BNE_REL;
g_c[5] = 9; // 3 + 6
g_c += 6;
add_call(popax); // 3 instructions
// See if first operand is 0.
g_c[0] = I_STX_ZPG;
g_c[1] = (uint8_t) &tmp1;
g_c[2] = I_ORA_ZPG;
g_c[3] = (uint8_t) &tmp1;
// If so, skip setting A to 1. A contains 0.
g_c[4] = I_BEQ_REL;
g_c[5] = 2; // The LDA below.
g_c += 6;
// Set A to 1.
g_c[0] = I_LDA_IMM; // The BNE arrives here.
g_c[1] = 1;
g_c[2] = I_LDX_IMM; // The BEQ arrives here.
g_c[3] = 0;
g_c += 4;
break;
case OP_OPEN_PARENS:
// No-op.
break;
@ -534,6 +594,10 @@ static uint8_t *compile_expression(uint8_t *s) {
op = OP_MULT;
} else if (*s == T_SLASH) {
op = OP_DIV;
} else if (*s == T_AND) {
op = OP_AND;
} else if (*s == T_OR) {
op = OP_OR;
} else if (*s == T_EQUAL) {
if (s[1] == T_LESS_THAN) {
s += 1;
@ -1270,7 +1334,7 @@ int16_t main(void)
int16_t a, b, c;
b = 5;
c = 6;
a = b == c;
a = b && c;
}
*/