Routines
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6E3C: Check whether a boy can be seen by a teacher
Used by the routines at 6F1E, 7000 and F41F. Returns with the carry flag set if the boy can be seen by a teacher, and the teacher's character number in H'.
Input
H 0xA7 (BOY WANDER), 0xA8 (ANGELFACE) or 0xAC (ERIC)
6E3C CALL \$6E90 Get the floor (0x9B, 0xA2, 0xA9) nearest to the character in D
This entry point is used by the routine at 77AC.
6E3F CALL \$6EA7 Get the teacher's visibility range in [C,B]
6E42 EXX
6E43 LD B,\$04 There are 4 teachers
6E45 LD H,\$A3 And the first is 0xA3=MR WACKER
6E47 LD L,\$62 Collect the teacher's x-coordinate from byte 0x62 of his buffer
6E49 LD A,(HL)
6E4A EXX
6E4B CP B Is the teacher at or to the left of the upper bound of the visibility range?
6E4C JR Z,\$6E57 Jump if so
6E4E JR C,\$6E57
6E50 EXX
6E51 INC H Next teacher
6E52 DJNZ \$6E47 Jump back until all four teachers are done
6E54 AND A Clear the carry flag to indicate that the boy wasn't seen by a teacher
6E55 EXX
6E56 RET
6E57 CP C Is the teacher to the left of the lower bound of the visibility range?
6E58 JR C,\$6E50 Jump back to consider the next teacher if so
The teacher's x-coordinate is within the visibility range [C,B]. Now check his y-coordinate.
6E5A EXX
6E5B LD L,\$70 Is there an uninterruptible subcommand routine address in bytes 0x6F and 0x70 of the teacher's buffer?
6E5D LD A,(HL)
6E5E AND A
6E5F JR NZ,\$6E51 Jump back to consider the next teacher if so (this one is occupied)
6E61 LD L,\$61 Collect the teacher's y-coordinate from byte 0x61 of his buffer
6E63 LD A,(HL)
6E64 INC L L=0x62
6E65 EXX
6E66 CP \$9E Is the teacher near or on the top floor?
6E68 JR NC,\$6E6E Jump if not
6E6A LD A,\$9B This is the y-coordinate of the top floor
6E6C JR \$6E76
6E6E CP \$A5
6E70 LD A,\$A2 This is the y-coordinate of the middle floor
6E72 JR C,\$6E76 Jump if the teacher is near or on the middle floor
6E74 LD A,\$A9 This is the y-coordinate of the bottom floor
6E76 CP D Is the teacher within the y-coordinate visibility range?
6E77 JR NZ,\$6E50 Jump back to consider the next teacher if not
The teacher is close enough to the boy to see him. But is the teacher facing the right way?
6E79 EXX
6E7A LD A,(HL) A=teacher's x-coordinate
6E7B EXX
6E7C CP E Is the teacher standing right where the boy is?
6E7D SCF Return with the carry flag set if so
6E7E RET Z
6E7F CP E A=0x80 if the boy is to the right of the teacher, 0x00 if the boy is to the left
6E80 LD A,\$00
6E82 RRA
6E83 EXX
6E84 LD L,\$60 Byte 0x60 of the teacher's buffer holds his animatory state
6E86 XOR (HL) Reset bit 7 of A if the teacher is facing the boy
6E87 LD L,\$62
6E89 EXX
6E8A RLCA Push bit 7 of A into the carry flag
6E8B CCF Return with the carry flag set if the teacher is facing the boy
6E8C RET C
6E8D JR \$6E50 Otherwise consider the next teacher
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