3. Syntax Overview
Sym language commands are divided into six categories: stack operations, arithmetic operations, comparison, control flow, input/output, and debugging.
3.1 Stack Operations
Sym language uses a stack to manipulate data. Below are the commands related to stack operations.
| Command | Description | Usage example |
|---|---|---|
_ | Remove the value at the top of the stack. | _ |
@ | Copy the value at the top of the stack. | @ |
& | Swap the two values at the top of the stack. | & |
n | Push n onto the stack (e.g. 10). | 10 |
3.2 Arithmetic Operations
Sym language allows basic arithmetic operations to be performed on numbers in the stack. Arithmetic commands use the value at the top of the stack to perform operations.
| Command | Description | Example |
|---|---|---|
+ | Add the two values on the top of the stack. | + |
- | Subtract the two values on the top of the stack. | - |
* | Multiply the two values on the top of the stack. | * |
/ | Divide the two values on the top of the stack. | / |
% | Calculate the remainder of the two values on the top of the stack. | % |
3.3 Comparison Operations
The Sym language provides instructions for comparing values. These instructions compare the values on the top of the stack and push the result onto the stack (1 or 0).
| Command | Description | Example |
|---|---|---|
= | Compare whether the two values on the top of the stack are equal. | = |
> | Is the top value of the stack greater than the second value? | > |
< | Is the top value of the stack less than the second value? | < |
3.4 Control Flow
Control flow commands allow you to branch program execution. They allow you to jump or loop based on certain conditions.
| Command | Description | Usage example |
|---|---|---|
^n | Unconditionally jump to the specified line number n. | ^10 |
|n | If the top of the stack is 0, jump to line number n. | |10 |
~n | If the top of the stack is not 0, jump to line number n. | ~10 |
; | Stop the program. | ; |
3.5 Input/Output
The Sym language provides basic input/output commands. These allow you to receive values from standard input and display values on standard output.
| Command | Description | Example |
|---|---|---|
? | Receive a single value from standard input and push it onto the stack. | ? |
! | Print the top value on the stack to standard output. | ! |
3.6 Debugging
There are also several debugging commands. You can check the state of the stack while the program is running, and input and output debugging information.
| Command | Description | Example |
|---|---|---|
$? | Receive a number from standard input and push it onto the stack. | $? |
$! | Print the top value on the stack for debugging purposes. | $! |
3.7 Comments
A line is a comment only if the first character of the line is #.
The Sym language instruction set is designed to be simple and intuitive. Understanding these basic instructions will give you the foundations of programming in the Sym language.