kep-hack/engine/pokemon/experience.asm
2020-11-14 20:52:10 -06:00

150 lines
2.8 KiB
NASM

; calculates the level a mon should be based on its current exp
CalcLevelFromExperience::
ld a, [wLoadedMonSpecies]
ld [wd0b5], a
call GetMonHeader
ld d, $1 ; init level to 1
.loop
inc d ; increment level
call CalcExperience
push hl
ld hl, wLoadedMonExp + 2 ; current exp
; compare exp needed for level d with current exp
ldh a, [hExperience + 2]
ld c, a
ld a, [hld]
sub c
ldh a, [hExperience + 1]
ld c, a
ld a, [hld]
sbc c
ldh a, [hExperience]
ld c, a
ld a, [hl]
sbc c
pop hl
jr nc, .loop ; if exp needed for level d is not greater than exp, try the next level
dec d ; since the exp was too high on the last loop iteration, go back to the previous value and return
ret
; calculates the amount of experience needed for level d
CalcExperience::
ld a, [wMonHGrowthRate]
add a
add a
ld c, a
ld b, 0
ld hl, GrowthRateTable
add hl, bc
call CalcDSquared
ld a, d
ldh [hMultiplier], a
call Multiply
ld a, [hl]
and $f0
swap a
ldh [hMultiplier], a
call Multiply
ld a, [hli]
and $f
ldh [hDivisor], a
ld b, $4
call Divide
ldh a, [hQuotient + 1]
push af
ldh a, [hQuotient + 2]
push af
ldh a, [hQuotient + 3]
push af
call CalcDSquared
ld a, [hl]
and $7f
ldh [hMultiplier], a
call Multiply
ldh a, [hProduct + 1]
push af
ldh a, [hProduct + 2]
push af
ldh a, [hProduct + 3]
push af
ld a, [hli]
push af
xor a
ldh [hMultiplicand], a
ldh [hMultiplicand + 1], a
ld a, d
ldh [hMultiplicand + 2], a
ld a, [hli]
ldh [hMultiplier], a
call Multiply
ld b, [hl]
ldh a, [hProduct + 3]
sub b
ldh [hProduct + 3], a
ld b, $0
ldh a, [hProduct + 2]
sbc b
ldh [hProduct + 2], a
ldh a, [hProduct + 1]
sbc b
ldh [hProduct + 1], a
; The difference of the linear term and the constant term consists of 3 bytes
; starting at hProduct + 1. Below, hExperience (an alias of that address) will
; be used instead for the further work of adding or subtracting the squared
; term and adding the cubed term.
pop af
and $80
jr nz, .subtractSquaredTerm ; check sign
pop bc
ldh a, [hExperience + 2]
add b
ldh [hExperience + 2], a
pop bc
ldh a, [hExperience + 1]
adc b
ldh [hExperience + 1], a
pop bc
ldh a, [hExperience]
adc b
ldh [hExperience], a
jr .addCubedTerm
.subtractSquaredTerm
pop bc
ldh a, [hExperience + 2]
sub b
ldh [hExperience + 2], a
pop bc
ldh a, [hExperience + 1]
sbc b
ldh [hExperience + 1], a
pop bc
ldh a, [hExperience]
sbc b
ldh [hExperience], a
.addCubedTerm
pop bc
ldh a, [hExperience + 2]
add b
ldh [hExperience + 2], a
pop bc
ldh a, [hExperience + 1]
adc b
ldh [hExperience + 1], a
pop bc
ldh a, [hExperience]
adc b
ldh [hExperience], a
ret
; calculates d*d
CalcDSquared:
xor a
ldh [hMultiplicand], a
ldh [hMultiplicand + 1], a
ld a, d
ldh [hMultiplicand + 2], a
ldh [hMultiplier], a
jp Multiply
INCLUDE "data/growth_rates.asm"