ewancroft.uk / sigi
[READ-ONLY] Mirror of https://github.com/ewanc26/sigi.
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README.md

Sigi #

A pure symbolic stack language that compiles to C or runs in an interpreter.

Character set: !@#$%^&*()-+=[]{}|;:'",.<>/?\~ plus digits 0-9

All syntax is symbolic. No alphanumeric keywords. User-defined names are prefixed with ..

Also available on Tangled

Install #

pip install -e .

This installs the sigic compiler.

Usage #

# Interactive REPL
sigic

# Compile to C
sigic hello.si -o hello.c

# Compile and run
sigic hello.si --run

# Reference interpreter (faster startup)
sigic hello.si --interpret

# Debug — show tokens or AST
sigic hello.si --emit-tokens
sigic hello.si --emit-ast

Symbol reference #

Symbol Name Effect
!N PUSH Push number N (int or float)
@ DUP Duplicate top of stack
# SWAP Swap top two elements
$ DROP Discard top of stack
+ ADD Pop b, pop a → push a + b
- SUB Pop b, pop a → push a - b
* MUL Pop b, pop a → push a * b
/ DIV Pop b, pop a → push a / b
% MOD Pop b, pop a → push fmod(a, b)
= EQ Pop b, pop a → push 1 if equal, else 0
< LT Pop b, pop a → push 1 if a < b
> GT Pop b, pop a → push 1 if a > b
~ NOT Pop a → push 1 if zero, else 0
| PRINT Pop and print as number
^ PRINTC Pop and print as character
? INPUT Read number from stdin
: STORE Pop address, pop value → store to var
:.name STOREN Pop value → store to named variable
.name LOADN Push value of named variable or call function
<n> LOAD Push value of variable n (digits 0-99)
[ body ] WHILE Loop while stack top nonzero
{ then ; else } IF-ELSE Pop condition, execute then or else
{N body } FUNC Define function N (0-99)
{.name body } FUNCN Define named function
(N) CALL Call function N
(.name) CALLN Call named function
"text" STRING Print characters
'x CHAR Push character code
\\ COMMENT Line comment
/* body */ BLOCK COMMENT Multi-line comment
S SIN Pop a → push sin(a)
C COS Pop a → push cos(a)
T TAN Pop a → push tan(a)
R SQRT Pop a → push sqrt(a)
P POW Pop exp, pop base → push pow(base, exp)
F FLOOR Pop a → push floor(a)
L LOG Pop a → push log(a)
E EXP Pop a → push exp(a)
M ABS Pop a → push fabs(a)
N ATAN2 Pop y, pop x → push atan2(y, x)
W RAND Push random 0.0-1.0
X EXIT Pop code → exit program
Z TIME Push current time in seconds
_ AINIT Pop id, pop size → initialize array
K AFREE Pop id → free array
O FILE_OPEN Pop mode, pop len, pop chars → fd
G FILE_READ Pop fd, pop size → push bytes, read_len
H FILE_WRITE Pop fd, pop size, pop data → bytes_written
Y FILE_CLOSE Pop fd → close
A ALOAD Pop idx, pop id → push array[idx]
a ASTORE Pop idx, pop id, pop val → array[idx] = val
U USLEEP Pop microseconds → sleep

Error handling #

  • Checks for undefined function calls and redefinitions before compiling
  • All errors (Lex, Parse, Semantic, Runtime) include line, column, source snippet, and pointer
  • Reference interpreter provides a second implementation for verification

Examples #

Named identifiers #

{.greet "Hello!\n"}
(.greet)

!42 :.answer
.answer |  \\ prints 42

File I/O #

!116 !101 !115 !116 !46 !116 !120 !116 !8 !1 O :.my_fd
!116 !101 !115 !116 !4 .my_fd H $
.my_fd Y

Design #

Every operation is a single character. No reserved words — only punctuation. Stack-based with postfix notation, making parsing trivial.

Inspired by Forth, Joy, and other concatenative languages.