php-basic

Basic language interpreter in PHP

• supports both numeric (old-style) and literal (with colon) labels.
• variables can hold numeric and string values
• multi-dimension arrays with zero-based indices
• calculated goto (both with numeric and text labels)

interactive mode (REPL) is not added yet, mainly due to lack of usage for it

Supported statements

We follow "mainstream" from original (Dartmouth) BASIC which was also widely found in "home computers era", like Apple, Commodore, ZX Spectrum.

• IF ... THEN (no else, multiple statements per line, old-school style)
• PRINT with commans and semicolons
• INPUT automatically deciding on type of value (numeric or string)
• GOTO and GOSUB allowing expression as argument, RETURN
• FOR and NEXT statements (with optional positive STEP)
• READ, DATA and RESTORE
• DIM allocating arrays
• DEF for defining custom functions
• LET which could be omitted in assignment
• END which just stops the program
• REM skips till the end of line

Supported operations

+ - * / MOD
^ (power)
> < = <> >= <= (true represented by 1, false by 0)
AND OR

Supported built-in functions

Numerical functions:

ABS SGN INT
SIN COS TAN ATN
EXP SQR LOG - first two could also be represented with power operator
RND - requires argument but ignores it

Text functions: ASC CHR - character to code - and back conversion MID LEFT RIGHT - taking substrings LEN

Extra features yet to come

• arrays declared with no dimension to serve as hashtables (e.g. using string variables)

Javascript Executor

As program execution consists of two steps (slightly not in the mood of interpreted BASIC) - parsing and running, we provide Javascript runner, which can take parsed code (in form of JSON) as input. To export parsed code we still need PHP first, for example:

PARSED_JS=js/parsed.js php main.js someprogram.bas

This feature has specific intended usage (running in-browser visualization for "arcade" type of coding problems) so probably it is of no interest for general user.