FrogLang

FrogLang is a programming language that is:

• stack based
• concatenative
• statically typed
• compiled to C

Requirements

Building FrogLang requires a POSIX environment, just, and a C11-capable GCC installation. The repository's devenv configuration provides these tools together with the Python formatting and type-checking tools used by the test suite.

Quick start

just frogc-seed
build/frogc -h
build/frogc check examples/01_simple.frog
build/frogc fmt examples/01_simple.frog
build/frogc inspect examples/01_simple.frog
build/frogc cursor --byte 0 examples/01_simple.frog
build/frogc run examples/01_simple.frog

Every module permits declarations only at the top level. Every root program must define exactly one func main -- do ... end with no inputs or outputs; empty and declaration-only root sources are invalid.

Command-line interface

build/frogc -h shows CLI help. With no arguments, build/frogc is a compiler filter: it reads Frog source from standard input and writes generated C to standard output. check performs full semantic analysis without generating C; it reads the named file, or standard input when no file is given. fmt accepts input the same way and writes stack-aware indentation to standard output without changing the source file or adding line breaks. See the formatter reference. inspect prints the analyzed program for developer tools. Pass --builtins to include implicitly imported builtin function bodies. Pass --lexemes to include lossless source lexemes and syntax regions; both options may be combined. cursor --byte OFFSET [FILE] reports semantic identities, visible names, and typed stacks at a root-source byte position. These versioned outputs are diagnostic interfaces and may change between versions. See the compiler inspection reference and semantic cursor reference. Imported module paths are relative to the root source directory. run writes reusable scratch artifacts under build/, compiles them, and executes the binary. build writes the source-adjacent .c and executable directly; build -r runs the resulting executable.

Prefix a filter, check, fmt, inspect, cursor, run, or build invocation with --debug to trace compile-time type stacks to standard error. Use --release to omit calls to the implicit builtin assert while retaining operand evaluation. See the language reference for details.

Bootstrap

The checked fixed-point C bootstrap seed is compiler/frogc.c, so a C compiler is sufficient to bootstrap Frog:

just frogc-seed
build/frogc < compiler/frogc.frog > build/frogc.next.c
cmp compiler/frogc.c build/frogc.next.c

Run the complete two-generation fixed-point verification with:

just bootstrap-check

To bootstrap manually without Python:

mkdir -p build
gcc -std=c11 -pedantic -Wall -Wextra -Wconversion -Werror -O2 compiler/frogc.c -o build/frogc
build/frogc < compiler/frogc.frog > build/frogc.next.c

Documentation

• Language reference
• Standard library
• Stack-aware formatter
• Compiler inspection output
• Semantic cursor queries
• Testing and bootstrap verification
• VS Code support
• Examples

The complete documentation index is available in docs/README.md.