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Used by the routines at E_LINE_NO and DEC_TO_FP.
This subroutine returns a 'last value' on the calculator stack that is the result of converting an integer in a BASIC line, i.e. the integer part of the decimal number or the line number, to its floating-point form.
Repeated calls to CH_ADD_1 fetch each digit of the integer in turn. An exit is made when a code that does not represent a digit has been fetched.
A Code of the current character
A Code of the next non-digit character
INT_TO_FP 2D3B PUSH AF Save the first digit - in A.
2D3C RST $28 Use the calculator.
2D3D DEFB $A0 stk_zero: (the 'last value' is now zero)
2D3E DEFB $38 end_calc
2D3F POP AF Restore the first digit.
Now a loop is set up. As long as the code represents a digit then the floating-point form is found and stacked under the 'last value' (V, initially zero). V is then multiplied by 10 and added to the 'digit' to form a new 'last value' which is carried back to the start of the loop.
NXT_DGT_2 2D40 CALL STK_DIGIT If the code represents a digit (D) then stack the floating-point form; otherwise return.
2D43 RET C
2D44 RST $28 Use the calculator.
2D45 DEFB $01 exchange: D, V
2D46 DEFB $A4 stk_ten: D, V, 10
2D47 DEFB $04 multiply: D, 10*V
2D48 DEFB $0F addition: D+10*V
2D49 DEFB $38 end_calc: D+10*V (this is 'V' for the next pass through the loop)
2D4A CALL CH_ADD_1 The next code goes into A.
2D4D JR NXT_DGT_2 Loop back with this code.
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