Enhanced BASIC, useful routines By Lee Davison.

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.

Note that most, if not all, of these routines need EhBASIC to be initialised before they will work properly and can not be used in isolation from EhBASIC.

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.

Last page update: 14th July, 2003.

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