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 increment the execute 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_XERR

With d0 set, do error #d0, then warm start.

The equivalent can be achieved by calling the routine in the name column.

Name	d0	Error	Name	d0	Error
LAB_NFER	$00	NEXT without FOR	LAB_SNER	$04	syntax
LAB_RGER	$08	RETURN without GOSUB	LAB_ODER	$0C	out of data
LAB_FCER	$10	function call	LAB_OFER	$14	overflow
LAB_OMER	$18	out of memory	LAB_USER	$1C	undefined statement
LAB_ABER	$20	array bounds	LAB_DDER	$24	double dimension array
LAB_DZER	$28	divide by 0	LAB_IDER	$2C	illegal direct
LAB_TMER	$30	type mismatch	LAB_SLER	$34	string too long
LAB_SCER	$38	string too complex	LAB_CCER	$3C	can't continue
LAB_UFER	$40	undefined function	LAB_LDER	$44	LOOP without DO
LAB_UVER	$48	undefined variable	LAB_UDER	$4C	undimensioned array
LAB_WDER	$50	wrong dimensions	LAB_ADER	$54	address

You may add your own error messages by extending the error message pointer and error message tables.

LAB_INLN

Print "? " and get BASIC input. Returns a0 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 a0 if found, if not it returns carry and a pointer to the next numbered line in a0.

LAB_SHLN

Search Basic for temporary integer line number from a0. Same as above but starts the search from a0.

LAB_SNBS

Scan for next BASIC statement (: or [EOL]). Returns d1 as index to : or [EOL] from (a5).

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 d0 to output device.

LAB_GVAR

Get variable address. Returns a pointer to the variable in Cvaral and a0 and sets the data type flag, $80=string, $40=integer and $00=float.

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 d0 as the next byte. If so return here, else 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 d0 and Itemp.

LAB_EVPI

Evaluate +ve integer expression.

LAB_EVIR

Evaluate integer expression, no sign check.

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_SGBY

Scan and get byte parameter, return the byte in d0 and Itemp.

LAB_GTBY

Get byte parameter and ensure numeric type, else do type mismatch error. Return the byte in d0 and Itemp.

LAB_EVBY

Evaluate byte expression, return the byte in d0 and Itemp.

LAB_GADB

Get two parameters as in POKE or WAIT. Return the first parameter in a0, second in d0.

LAB_SCGB

Scan for "," and get byte, else do Syntax error then warm start. Return the byte in d0 and Itemp.

LAB_UFAC

Unpack the four bytes starting (a0) into FAC1 as a floating point number.

LAB_PFAC

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

LAB_AYFC

Convert d0 to signed longword in FAC1.

LAB_RTST

Put string address and length on descriptor stack & update stack pointers. Pointer is in a0, length is in d1. This is how you return a string to BASIC.

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