Routines
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71EA: Match a command against an action table entry
Compares the verb, particle and preposition in an action table entry (at HL) with those of the parsed command (at IY) using 7225. The verb must match. The particle and preposition may match in the same order, or crossed over, so that for example both 'take off the ring' and 'take the ring off' find the TAKE OFF action.
Returns with Z set for a match; A is 0 if the words matched in order and 1 if they were crossed over, and $B5D0 is set to 1 once the verb alone has matched (so the caller can tell 'wrong verb' from 'right verb, wrong words').
Input
HL Action table entry
IY Parsed command
Output
F Z set if they match
A 0 = in order, 1 = crossed over
71EA PUSH DE Save the caller's DE, HL and IY
71EB PUSH HL
71EC PUSH IY
71EE CALL $7225 Do the verbs match? (this also moves both pointers on to their next word)
71F1 JR NZ,$7220 No: there is no match at all - give up straight away
71F3 LD A,$01 Record that at least the verb has matched...
71F5 LD ($B5D0),A ...so a later failure can be blamed on "the wrong words", not "an unknown verb"
71F8 CALL $7225 Do the particles match, in the same order?
71FB JR NZ,$7204 No: they might just be the wrong way round - go and check that below
71FD CALL $7225 They do: now do the prepositions match too, in the same order?
7200 LD A,$00 If so, this is a plain, in-order match
7202 JR Z,$7220 ...so finish here, with A=0
7204 POP IY Not a straightforward match: restore the command's own pointer...
7206 POP HL ...and the action-entry's pointer, saved right at the very start...
7207 PUSH HL ...pushing them straight back so they can be recovered again below
7208 PUSH IY
720A LD DE,$0004 Move the command's pointer on 4 bytes, to its own preposition word...
720D ADD IY,DE
720F INC HL ...and the action-entry's pointer on 2, to its particle word instead
7210 INC HL
7211 CALL $7225 Does the entry's PARTICLE match the command's own PREPOSITION?
7214 JR NZ,$7220 No: there is no match, in either order
7216 LD DE,$FFFC Move the command's pointer back 4, to its own particle word...
7219 ADD IY,DE
721B CALL $7225 ...and does THAT match the entry's PREPOSITION?
721E LD A,$01 Yes: it is a match, but with particle and preposition crossed over
7220 POP IY Restore the caller's IY, HL and DE
7222 POP HL
7223 POP DE
7224 RET
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