Simply

Simply is an experimental programming language focused on explicit, readable code. The GitHub repository is named Simpy, but the language is Simply.

Simply 0.2

STRING name = INPUT("Name: ")
INT age = INPUT("Age: ")
BOOL access = True

IF age >= 18 AND access:
    DISPLAY("Welcome", name)
ELSE IF age >= 13:
    DISPLAY("Teen access")
ELSE:
    DISPLAY("Blocked")

END

v0.2 includes:

• ELSE IF
• AND, OR, NOT
• INPUT(...)
• WHILE
• isolated TEST(...) blocks

It intentionally does not include FOR, EXPECT, functions, RETURN, BREAK, CONTINUE, lists, or classes yet.

Install

After the first PyPI release, install the Simply runtime from any terminal:

python -m pip install simply-lang

Then run .sim files from any folder:

simply program.sim

Run test blocks with:

simply test program.sim

For local development from a clone of this repository:

python -m pip install -e .

VS Code

After the Marketplace release, install editor support with:

code --install-extension gamasdorpg.simply-language-support

Then .sim files are recognized as Simply anywhere. Ctrl+K M will list Simply as a language mode, and the extension provides syntax highlighting plus live lexer/parser/type diagnostics in the Problems panel.

The extension no longer needs a cloned Simpy repository. It communicates with the installed runtime through:

simply diagnostics

If the CLI is installed outside VS Code's PATH, set Simply: Executable Path in VS Code.

Until the Marketplace release is published, repository development can still use the local extension tooling.

Architecture

.sim source
    ↓
Lexer
    ↓
Tokens + INDENT/DEDENT
    ↓
Recursive-descent Parser
    ↓
AST
    ↓
Semantic Analyzer + Symbol Scopes
    ↓
Tree-walking Interpreter
    ↓
Runtime
    ↓
Output

The implementation is written in Python 3.10+ and has no third-party runtime dependencies.

INPUT

The declared variable type determines how input is converted:

INT age = INPUT("Age: ")
FLOAT score = INPUT("Score: ")
STRING name = INPUT("Name: ")
BOOL ready = INPUT("Ready (True/False): ")

WHILE

INT x = 0

WHILE x < 5:
    DISPLAY(x)
    x = x + 1

END

TEST

Tests are isolated and receive copies only of the variables listed in TEST(...).

INT x = 10
INT y = 2

TEST(x, y):
    x = x + y
    DISPLAY(x)
END

DISPLAY(x)
END

Normal execution skips test blocks. Test mode executes them.

Quality checks

Run the Python test suite:

python -m unittest discover -s tests -v

GitHub Actions also verifies the Python package build and packages the VS Code extension as a VSIX on pushes and pull requests.

Publishing

See DISTRIBUTION.md for the complete PyPI and Visual Studio Marketplace release procedure.

Project layout

simply/
    tokens.py
    lexer.py
    parser.py
    ast_nodes.py
    semantic.py
    typesys.py
    environment.py
    interpreter.py
    runtime.py
    runner.py
    diagnostics.py
    cli.py

main.py
LANGUAGE_SPEC.md
DISTRIBUTION.md
examples/
tests/
.vscode/
vscode-extension/

See LANGUAGE_SPEC.md for the exact v0.2 rules.