Enhanced BASIC, useful routines by Lee Davison
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Introduction.

There are many subroutines within BASIC that can be useful if you wish to use your own assembly routines with it. Here are some of them with a brief description of their function. For full details see the source code.

LAB_IGBY

BASIC increment and get byte routine. gets the next byte from the BASIC command stream. If the byte is a numeric character then the carry flag will be set, if the byte is a termination byte, either null or a statement separator, then the zero flag will be set. Spaces in the command stream will automatically be ignored.

LAB_GBYT

BASIC get byte routine. Gets the current byte from the BASIC command stream but does not change the pointer. Otherwise the same as above.

LAB_COLD

Performs a cold start. BASIC is reset and all BASIC memory is cleared.

LAB_WARM

Performs a warm start. Execution is stopped and BASIC returns to immediate mode.

LAB_OMER

Do "Out of memory" error, then warm start. The same as error $0C below.

LAB_XERR

With X set, do error #X, then warm start.

X	Error	X	Error
$00	NEXT without FOR	$02	syntax
$04	RETURN without GOSUB	$06	out of data
$08	function call	$0A	overflow
$0C	out of memory	$0E	undefined statement
$10	array bounds	$12	double dimension array
$14	divide by 0	$16	illegal direct
$18	type mismatch	$1A	long string
$1C	string too complex	$1E	continue error
$20	undefined function	$22	LOOP without DO

LAB_INLN

Print "? " and get BASIC input. Returns XY (low/high) as a pointer to the start of the input line. The input is null terminated.

LAB_SSLN

Search Basic for a line, the line number required is held in the temporary integer, from start of program memory. Returns carry set and a pointer to the line in Baslnl/Baslnh if found, if not it returns carry and a pointer to the next numbered line in Baslnl/Baslnh.

LAB_SHLN

Search Basic for temporary integer line number from AX. Same as above but starts the search from AX (low/high).

LAB_SNBS

Scan for next BASIC statement (: or [EOL]). Returns Y as index to : or [EOL] from (Bpntrl).

LAB_SNBL

Scan for next BASIC line. Same as above but only returns on [EOL].

LAB_REM

Perform REM, skip (rest of) line.

LAB_GFPN

Get fixed-point number into temporary integer.

LAB_CRLF

Print [CR]/[LF] to output device.

LAB_PRNA

Print character in A to output device.

LAB_GVAR

Get variable address. Returns a pointer to the variable in Lvarpl/h and sets the data type flag, $FF=string, $00=numeric.

LAB_EVNM

Evaluates an expression and checks the result is numeric, if not it does a type mismatch. The result of the expression is returned in FAC1.

LAB_CTNM

Check if source is numeric, else do type mismatch.

LAB_CTST

Check if source is string, else do type mismatch.

LAB_CKTM

Type match check, set carry for string, clear carry for numeric.

LAB_EVEX

Evaluate expression.

LAB_GVAL

Get numeric value from line. Returns the result in FAC1.

LAB_SCCA

Scan for the byte in A as the next byte. If so return here, else do syntax error then warm start.

LAB_SNER

Do syntax error, then warm start.

LAB_CASC

Check byte is alpha ("A" to "Z" or "a" to "z"), return carry clear if so.

LAB_EVIN

Evaluate integer expression. Return integer in FAC1_3/FAC1_2 (low/high).

LAB_EVPI

Evaluate +ve integer expression.

LAB_EVIR

Evaluate integer expression, check is in range -32786 to 32767

LAB_FCER

Do function call error, then warm start.

LAB_CKRN

Check that the interpreter is not in immediate mode. If not then return, if so do illegal direct error.

LAB_GARB

Perform garbage collection routine.

LAB_EVST

Evaluate string.

LAB_ESGL

Evaluate string, return string length in Y.

LAB_SGBY

Scan and get byte parameter, return the byte in X.

LAB_GTBY

Get byte parameter and ensure numeric type, else do type mismatch error. Return the byte in X.

LAB_EVBY

Evaluate byte expression, return the byte in X.

LAB_GADB

Get two parameters as in POKE or WAIT. Return the byte (second parameter) in X and the integer (first parameter) in the temporary integer pair, Itempl/Itemph.

LAB_SCGB

Scan for "," and get byte, else do Syntax error then warm start. Return the byte in X.

LAB_F2FX

New convert float to fixed routine. accepts any value that fits into 24 bits, +ve or -ve and converts it into a right truncated integer in the temporary integer pair, Itempl/Itemph.

LAB_UFAC

Unpack the four bytes starting (AY) into FAC1 as a floating point number.

LAB_PFAC

Pack the floating point number in FAC1 into the current variable (Lvarpl).

LAB_STFA

Stores a 16 bit number in FAC1. Set X to the exponent required (usually $90) and the carry set for +ve numbers and clear for -ve numbers. The routine will clear FAC1 mantissa3 and then normalise it.

LAB_AYFC

Save integer AY (A = high byte, Y = low byte) in FAC1 and convert to float. The result will be -32768 to +32767.

LAB_MSSP

Make string space A bytes long. This returns the following. str_ln = A = string length str_pl = Sutill = string pointer low byte str_ph = Sutilh = string pointer high byte

LAB_RTST

Return string. Takes the string described instr_ln, str_pl and str_ph and puts it on the string stack. This is how you return a string to BASIC.

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