158 lines
3.2 KiB
ArmAsm
158 lines
3.2 KiB
ArmAsm
;; Parse a number from the input buffer at (basic_current_statement_ptr)
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;; Result is put into FAC1.
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;; basic_current_statement_ptr is updated with first position after the number.
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;; XXX - Remember decimal position and exponent, and apply them
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;; after to produce normalised floating point number.
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;; XXX - Doesn't use routines to access memory under ROMs etc.
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;; This is important, because this routine operates on numbers in BASIC text.
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ij_not_a_digit:
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;; XXX check for "." or "E"
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;; Other chars terminate the accumulation.
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;; Look for exponentiation marker
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;; XXX - Implement me!
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;; Probably should have a flag so that we know if we are accumulating
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;; exponent or mantissa digits
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;; Look for decimal point
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cmp #$2e
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bne ij_not_decimal
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lda tokenise_work4
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cmp #$ff
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beq ij_found_decimal
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;; More than one decimal point in a number means we have reached the end of the number
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clc
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rts
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ij_found_decimal:
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;; Found decimal.
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;; Thus start counting digits after the decimal, so that we
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;; can do the necessary number of divide by 10s on the final
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;; number.
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lda #$00
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sta tokenise_work4
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jmp ij_consider_next_digit
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ij_not_decimal:
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CLC
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RTS
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injest_number:
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;; Clear FAC1
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jsr erase_fac1
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;; Clear decimal position flag
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lda #$ff
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sta tokenise_work4
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;; Check if leading char is a - sign
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;; Note: the - will have been tokenised to $AB
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;; XXX - implement
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ldy #$00
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lda (basic_current_statement_ptr),y
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cmp #$AB
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bne ij_not_minus
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;; Set sign to negative
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lda #$ff
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sta basic_fac1_sign
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;; Skip over the minus sign
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jsr basic_consume_character
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ij_not_minus:
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ij_loop1:
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ldy #$00
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lda (basic_current_statement_ptr),y
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cmp #$30
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bcc ij_not_a_digit
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cmp #$3a
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bcs ij_not_a_digit
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;; It is a digit
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;; Only add digit if we have not overflowed the accuracy of
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;; the mantissa
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lda basic_fac1_exponent
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beq ij_accept_precision
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;; We have an extra digit after saturating our precision.
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;; Thus we should ignore the digit, and just multiply the FAC
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;; by 10, but only if we have not seen a decimal point.
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;; If we have seen a decimal point, then we can completely ignore
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;; the digit, as it is contributing not recordable information
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lda tokenise_work4
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cmp #$ff
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bne ij_seen_decimal_point
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jsr fac1_mul10
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;; Fall through
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ij_seen_decimal_point:
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jmp ij_consider_next_digit
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ij_accept_precision:
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;; We can accept more precision, so multiply the mantissa by 10, so that
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;; we can add the new digit in
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jsr fac1_mul10
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lda basic_fac1_exponent
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bne ij_consider_next_digit
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;; Get digit
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ldy #$00
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lda (basic_current_statement_ptr),y
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sec
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sbc #$30
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;; Add to FAC1 mantissa
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clc
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adc basic_fac1_mantissa+0
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sta basic_fac1_mantissa+0
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ldx #1
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ldy #3
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ij_loop2:
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lda basic_fac1_mantissa,x
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adc #$00
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sta basic_fac1_mantissa,x
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inx
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dey
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bne ij_loop2
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bcc +
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;; Carry set, so we have overflowed.
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;; We should shift everything right one digit, and increase
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;; the exponent by one. The non-zero exponent tells us that we
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;; can't fit any more precision in.
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jsr fac1_mantissa_div2
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*
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ij_consider_next_digit:
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;; Consider next digit
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jsr basic_consume_character
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jmp ij_loop1
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rts
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erase_fac1:
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lda #$00
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ldx #8
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*
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sta basic_fac1_exponent,x
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dex
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bpl -
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sta basic_fac1_mantissa_lob
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rts
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