From 007cf3e6703967bc0df233abb4410a00c6b8ca62 Mon Sep 17 00:00:00 2001
From: Lawrence Kesteloot <lk@teamten.com>
Date: Sun, 5 Aug 2018 16:12:58 -0700
Subject: [PATCH] Add AND and OR.

---
 README.md |  2 +-
 main.c    | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 66 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 140ca2b..aaa1b14 100644
--- a/README.md
+++ b/README.md
@@ -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.
 
diff --git a/main.c b/main.c
index 3a8e975..ea2fd21 100644
--- a/main.c
+++ b/main.c
@@ -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;
     }
     */