initial

asm/twotrail.ant

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+; ── SWARM FORAGER ────────────────────────────
+; Random walk to find food, dead reckoning to
+; navigate home. Pheromone marks food for others.
+; Hit play, then try improving it!
+
+; ── Registers ──
+.alias dx   r1           ; x displacement from nest
+.alias dy   r2           ; y displacement from nest
+.alias ret  r3           ; return address for CALL
+
+; ── Pheromone ──
+.const PH_FOOD CH_RED      ; marks food locations
+.const PH_NEST CH_BLUE
+.const PHER_INIT 255
+.const PHER_DECAY 2
+; ── Roles (visible in simulation viewer) ──
+.tag 0 foraging
+.tag 1 homing
+
+; ──────────────────────────────────────────────
+main:
+    set r7 PHER_INIT
+loop:
+    CARRYING
+    JNE r0 0 go_home
+    TAG foraging
+
+; ── SEARCH: find food ─────────────────────────
+search:
+    SENSE FOOD
+    JNE r0 0 grab
+
+; if we are too far from the food, dont mark
+    JLT r7 PHER_DECAY smell_trail
+    SUB r7 PHER_DECAY
+; if there is already a trail here, dont mark
+    SNIFF PH_NEST HERE r0
+    JNE r0 0 smell_trail
+    MARK PH_NEST r7
+
+smell_trail:
+    SMELL PH_FOOD
+    JNE r0 0 step
+    SENSE EMPTY
+step:
+    CALL ret move_track
+    JMP loop
+
+grab:
+    CALL ret move_track
+    PICKUP
+    MARK PH_FOOD 255
+    SET r6 PHER_INIT
+    JMP loop
+
+; ── GO HOME: dead reckon toward nest ──────────
+go_home:
+    TAG homing
+; if we are too far from the food, dont mark
+    JLT r6 PHER_DECAY sense_nest
+    SUB r6 PHER_DECAY
+; if there is already a trail here, dont mark
+    SNIFF PH_FOOD HERE r0
+    JNE r0 0 sense_nest
+    MARK PH_FOOD r6
+sense_nest:
+    SENSE NEST
+    JNE r0 0 deliver
+smell_nest:
+    SMELL PH_NEST
+    JNE r0 0 move_track
+    RANDOM r0 4
+    JEQ r0 0 wander       ; 25% random to unstick walls
+    CALL ret home_dir
+    CALL ret move_track
+    JMP main
+wander:
+    SENSE EMPTY
+    CALL ret move_track
+    JMP main
+
+deliver:
+    CALL ret move_track
+    DROP
+    SET r7 PHER_INIT
+    JMP main
+
+; ══════════════════════════════════════════════
+; SUBROUTINES — CALL ret <label>, return JMP ret
+; ══════════════════════════════════════════════
+
+; home_dir: set r0 = direction toward nest
+home_dir:
+    SET r4 dx
+    JGT dx 0 hd_dxp
+    SET r4 0
+    SUB r4 dx
+hd_dxp:
+    SET r5 dy
+    JGT dy 0 hd_dyp
+    SET r5 0
+    SUB r5 dy
+hd_dyp:
+    JGT r5 r4 hd_y
+    JGT dx 0 hd_w
+    SET r0 2
+    JMP ret
+hd_w:
+    SET r0 4
+    JMP ret
+hd_y:
+    JGT dy 0 hd_n
+    SET r0 3
+    JMP ret
+hd_n:
+    SET r0 1
+    JMP ret
+
+; move_track: MOVE r0, then update dx/dy
+move_track:
+    MOVE r0
+    JEQ r0 1 mt_n
+    JEQ r0 2 mt_e
+    JEQ r0 3 mt_s
+    SUB dx 1
+    JMP ret
+mt_n:
+    SUB dy 1
+    JMP ret
+mt_e:
+    ADD dx 1
+    JMP ret
+mt_s:
+    ADD dy 1
+    JMP ret