ConvFloat

ConvOP1:
;;Output: HL is the 16-bit result.
    ld de,OP1
ConvFloat:
;;Input: DE points to the float.
;;Output: HL is the 16-bit result.
;;Errors: DataType if the float is negative or complex
;;        Domain if the integer exceeds 16 bits.
;;Timings:  Assume no errors were called.
;;  Input is on:
;;  (0,1)         => 59cc                        Average=59
;;  0 or [1,10)   => 120cc or 129cc                     =124.5
;;  [10,100)      => 176cc or 177cc                     =176.5
;;  [100,1000)    => 309cc, 310cc, 318cc, or 319cc.     =314
;;  [1000,10000)  => 376cc to 378cc                     =377
;;  [10000,65536) => 514cc to 516cc, or 523cc to 525cc  =519.5
;;Average case:  496.577178955078125cc
;;vs 959.656982421875cc
;;87 bytes

    ld a,(de)
    or a
    jr nz,ErrDataType
    inc de
    ld hl,0
    ld a,(de)
    inc de
    sub 80h
    ret c
    jr z,final
    cp 5
    jp c,enterloop
ErrDomain:
;Throws a domain error.
    bcall(_ErrDomain)
ErrDataType:
;Throws a data type error.
    bcall(_ErrDataType)
loop:
    ld a,b
    ld b,h
    ld c,l
    add hl,hl
    add hl,bc
    add hl,hl
    add hl,hl
    add hl,hl
    add hl,bc
    add hl,hl
    add hl,hl
enterloop:
    ld b,a
    ex de,hl
    ld a,(hl) \ and $F0 \ rra \ ld c,a \ rra \ rra \ sub c \ add a,(hl)
    inc hl
    ex de,hl
    add a,l
    ld l,a
    jr nc,$+3
    inc h
    dec b
    ret z
    djnz loop
    ld b,h
    ld c,l
    xor a
;check overflow in this mul by 10!
    add hl,hl \ adc a,a
    add hl,hl \ adc a,a
    add hl,bc \ adc a,0
    add hl,hl \ adc a,a
    jr nz,ErrDomain
final:
    ld a,(de)
    rrca
    rrca
    rrca
    rrca
    and 15
    add a,l
    ld l,a
    ret nc
    inc h
    ret nz
    jr ErrDomain