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.