lfe_io_write.erl - Compact Writer

Purpose: Write LFE terms in compact (non-pretty) format with depth limiting.

Location: src/lfe_io_write.erl Size: 156 LOC, 5.3KB

Module Classification: I/O support, compact formatting

Public API

term(Term) -> [char()]
term(Term, Depth) -> [char()]

Convert term to compact string representation. Located at lfe_io_write.erl:36-38.

Output Format

Data Types:

; Atoms
foo          → "foo"
'foo-bar'    → "foo-bar"
'|complex|'  → "|complex|"

; Numbers
42           → "42"
3.14         → "3.14"

; Strings
"hello"      → "\"hello\""

; Lists
(1 2 3)      → "(1 2 3)"
'()          → "()"

; Improper lists
(a . b)      → "(a . b)"

; Tuples
#(a b c)     → "#(a b c)"

; Binaries
#"bytes"     → "#\"bytes\""

; Maps
#M(a 1 b 2)  → "#M(a 1 b 2)"

Depth Limiting:

term([a, [b, [c, [d, [e]]]]], 3)
→ "(a (b (c ...)))"

The ... indicates truncation at depth limit.

Implementation

Main Dispatch (term/2 at lines 45-92):

term(Atom, _D) when is_atom(Atom) ->
    write_atom(Atom);
term(Number, _D) when is_number(Number) ->
    write_number(Number);
term(List, D) when is_list(List) ->
    write_list(List, D);
term(Tuple, D) when is_tuple(Tuple) ->
    write_tuple(Tuple, D);
term(Binary, D) when is_binary(Binary) ->
    write_binary(Binary, D);
term(Map, D) when is_map(Map) ->
    write_map(Map, D).

List Writing (write_list/2 at lines 95-123):

Handles:

• Empty lists: ()
• Proper lists: (a b c)
• Improper lists: (a . b)
• Depth limiting

Atom Quoting (write_atom/1 at lines 126-141):

Quotes atoms when necessary:

• Contains special characters
• Starts with uppercase
• Is a reserved word

Dependencies

• lists, io_lib (Erlang stdlib)

Used By

• lfe_io - Via print1/1,2
• lfe_error - Error formatting
• Internal modules - Debugging output

Special Considerations

No Line Breaks: Output is single-line (compact).

Performance: Optimized for speed over readability.

Erlang Compatibility: Output can be read by Erlang's erl_scan (mostly).