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README.md

This is a fork of ubasic with the aims of

  • Making it smaller (removing lots of the more memory expensive coding)
  • Bringing it up to ECMA55 and a bit beyond
  • Making it faster (pretokenisation etc)
  • Making it run on FUZIX boxen usefully

Currently

  • Negative numbers are now supported
  • Types for things are a bit clearer as they will matter
  • Upper or lower case is permitted
  • Errors in the original debugging code are fixed
  • Variables may now be A-Z or A0-A9..Z0-Z9 as per ECMA55
  • PRINT supports , for tab fields, ; for supressing newline
  • PRINT constant string length is unlimited
  • INPUT is added including support for a prompt
  • FOR NEXT now supports STEP as per ECMA55
  • PEEK() is now a function as in normal basic - X = PEEK(4)
  • STOP replaces the rather odd "END"
  • ABS() INT() and SGN() are implemented
  • REM works as in normal BASIC
  • DATA and RESTORE are supported but not yet READ !
  • AND and OR keywords work (but not yet NOT)
  • GOTO and GOSUB allow expressions ("computed GOTO")
  • GO SUB and GO TO are two tokens so can be spaced
  • PRINT TAB() (SPC() is not ECMA55 nor is PRINT AT)
  • String variables (A$-Z$ required)
  • LEFT$(), RIGHT$(), MID$(), CHR$()
  • VAL(),CODE()
  • LEN()
  • Proper print parsing (we don't allow PRINT ABC printing A then B then C. You must as in normal basic use ; or , .
  • Faster RETURN and loops - we save the tokenizer pointer rather than mucking about playing hunt the line number
  • Statements can be separated by :
  • Removed the existing IF THEN ELSE in favour of a traditional IF THEN and : usage (IF THEN IF THEN ELSE ELSE ... gets horrible to parse and the old code messed it up badly)
  • Arrays (1 or 2 dimensions required by ECMA55)
  • Stdio is not used
  • Logical expressions with AND and OR differently priorities to boolean & |
  • Introduce "mod" to replace use of % - which we may need for other stuff later
  • CLS
  • PRINT AT

In comparison with ECMA55, then apart from all the floaty stuff it's missing

  • Implicit dimensioning of arrays
  • The ^ operator (or ** equivalent)
  • RND
  • SQR
  • DEF FN / FN (single or no variable required by ECMA55)
  • READ
  • Unquoted data strings

Space saving work needed

  • Replace malloc() with a proper sbrk based basic allocator
  • Only prealloc A-Z/A$-Z$ pointers
  • Work out why factor and relation are so big - and shrink them
  • Why are input_statement and dim_statement so big ?
  • Maybe kill the line finding array
  • Fast way to walk lines
  • Pretokenize code to make smaller and faster
  • Switch to compiling ?

Other useful stuff to add

  • XOR
  • USR()
  • INKEY$
  • ON expr GO TO/SUB ... {ELSE}
  • ON ERROR
  • ON TIMER/SIGNAL
  • PAUSE
  • Short tokens "P." etc
  • DO WHILE
  • DO UNTIL
  • I/O streams PRINT# INPUT# OPEN# CLOSE# etc
  • Command mode
  • CLEAR
  • NEW
  • SAVE / LOAD / CHAIN
  • Unix syscall bindings 8)
  • Unify GOSUB/NEXT/etc stack so that RETURN wipes out next frames etc

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A compact near ECMA55 compliant BASIC derived from ubasic

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