lfe_internal.erl - Type and Form Validation

Purpose: Centralized knowledge of core forms, BIFs, guards, and types.

Location: src/lfe_internal.erl Size: 360 LOC, 14KB

Module Classification: Utilities, validation

Public API

Form Classification:

is_core_form(Name) -> boolean()
is_core_func(Name, Arity) -> boolean()
is_guard_func(Name, Arity) -> boolean()
is_bif(Name, Arity) -> boolean()
is_erl_bif(Name, Arity) -> boolean()
is_lfe_bif(Name, Arity) -> boolean()
is_type(Name, Arity) -> boolean()

Check if name/arity is a known form/function/type. Lines 32-89.

Core Forms

Special Forms (is_core_form/1 at lines 123-178):

is_core_form(quote) -> true;
is_core_form(cons) -> true;
is_core_form(car) -> true;
is_core_form(cdr) -> true;
is_core_form(list) -> true;
is_core_form(tuple) -> true;
is_core_form(binary) -> true;
is_core_form(map) -> true;
is_core_form(lambda) -> true;
is_core_form('match-lambda') -> true;
is_core_form(let) -> true;
is_core_form('let-function') -> true;
is_core_form('letrec-function') -> true;
is_core_form('let-macro') -> true;
is_core_form(progn) -> true;
is_core_form(if) -> true;
is_core_form('case') -> true;
is_core_form(receive) -> true;
is_core_form(after) -> true;
is_core_form(call) -> true;
is_core_form(try) -> true;
is_core_form('catch') -> true;
is_core_form(funcall) -> true;
is_core_form(_) -> false.

Guard Functions

Allowed in Guards (is_guard_func/2 at lines 201-267):

Type tests, comparisons, arithmetic, boolean operators, bitwise operators, etc.

is_guard_func(is_atom, 1) -> true;
is_guard_func(is_list, 1) -> true;
is_guard_func('==', 2) -> true;
is_guard_func('=:=', 2) -> true;
is_guard_func('+', 2) -> true;
is_guard_func('and', 2) -> true;
is_guard_func('or', 2) -> true;
...

Not Allowed: User-defined functions, most BIFs.

BIF Lists

Erlang BIFs (is_erl_bif/2 at lines 289-367):

Comprehensive list of Erlang's built-in functions.

LFE BIFs (is_lfe_bif/2 at lines 369-399):

LFE-specific functions in lfe module.

Type Names

Built-in Types (is_type/2 at lines 421-467):

is_type(any, 0) -> true;
is_type(none, 0) -> true;
is_type(atom, 0) -> true;
is_type(integer, 0) -> true;
is_type(float, 0) -> true;
is_type(list, 0) -> true;
is_type(list, 1) -> true;  % list(T)
is_type(tuple, 0) -> true;
is_type(map, 0) -> true;
...

Dependencies

• None (self-contained)

Used By

• lfe_eval - Validation
• lfe_translate - Validation
• lfe_lint - Validation
• lfe_macro - Form checking

Special Considerations

Central Authority: Single source of truth for "what's valid in LFE".

Frequently Updated: When adding language features, this module must be updated.

Performance: Functions are called frequently; must be fast (usually constant-time lookups).