Language Documentation

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A stack-based language. Words consume values from the stack and push results back.

• Case of words does not count, dup and DUP are the same.
• The notation ( before -- after ) shows a word's effect on the stack.

Editor

During typing, following shortcuts are working.

CTRL+S

Run code.

CTRL+I

Show trace tab.

CTRL+O

Show output tab.

CTRL+H

Show help tab.

Comments

(...)

Block scoped comment.

\ ...

Comment to the end of the line.

Numeric Operations

+

( n1 n2 -- n1+n2 )

Adds the top two numbers.

-

( n1 n2 -- n1-n2 )

Subtracts the top number from the second.

*

( n1 n2 -- n1*n2 )

Multiplies the top two numbers.

/

( n1 n2 -- n1/n2 )

Divides the second number by the top one.

= > <

( n1 n2 -- bool )

Pushes true or false after comparison.

String Operations

'+

( s1 s2 -- s1s2 )

Concatenates two strings.

'*

( s n -- s*n )

Repeats a string n times.

'=

( s1 s2 -- s1=s2 )

String comparison, returns boolean.

'LEN

( s -- n )

String length, returns number.

'I

( s n -- s[n] )

Char at index, returns string.

Boolean Logic

NOT

( bool -- !bool )

Inverts a boolean value.

Stack Manipulation

DUP

( a -- a a )

Duplicates the top stack item.

DROP

( a -- )

Removes the top stack item.

SWAP

( a b -- b a )

Swaps the top two stack items.

OVER

( a b -- a b a )

Copies the second item to the top.

5 9 over over > .s

--- PRINT-STACK ---
[0]: false
[1]: 9
[2]: 5
---

PICK

( .. xn..x0 n -- ..xn..x0 xn )

Copies the n-th item (0-indexed) to the top.

20 15 10 .s
(
[0]: 10
[1]: 15
[2]: 20 <---
)
2 pick .s
(
[0]: 20 <---
[1]: 10
[2]: 15
[3]: 20
)

EMPTY?

( -- bool )

Pushes boolean if the stack is empty.

STACK-LEN

( -- len )

Pushes the current stack depth.

Printing & Output

.

( a -- )

Pops and prints the top value.

.p or PRINT

( a -- a )

Prints the top value without affecting stack.

.s or PRINT-STACK

( -- )

Prints the entire stack non-destructively.

Definitions & Control Flow

: <name> ... ;

Defines a new word.

: SQUARE DUP * ;
5 SQUARE . ( prints 25 )

<cond> IF ... THEN

<cond> IF ... ELSE ... THEN

Conditional branching.

5 3 > IF "Bigger" . THEN
\OUTPUT: "Bigger"

3 5 > IF "Bigger" ELSE "Lesser" THEN .
\OUTPUT: "Lesser"

BEGIN ... <cond> UNTIL

Loops until the condition is true.

( Counts 0 to 4 )
0
BEGIN
  DUP . 1 +
  DUP 5 =
UNTIL

\OUTPUT: 0 1 2 3 4