The simplest expressions in every language are constants: atoms, strings, paths. (Strings and paths aren't all constants per se, because they have interpolations.)
Cold Atom
A constant, cold atom.
Syntax
Any warm atom form, prefixed with %.
AST
[%rock p=term q=*]
Discussion
A cold atom is one whose type is inferred to be of a single atom constant.
Examples
We can see the contrast with warm atoms by using the compiler parser function, ream:
> (ream '%hi')[%rock p=%tas q=26.984]> (ream '\'hi\'')[%sand p=%t q=26.984]> (ream '%12')[%rock p=%ud q=12]
Paths
Path with interpolation.
Syntax
/this/is/a/path
Produces
A null-terminated list of the items, which are either constant @ta atoms (knots), or expressions producing a knot.
Examples
> `path`/this/is/a/path/this/is/a/path> `path`/this/is/[`@ta`(cat 3 %a- %test)]/path/this/is/a-test/path> `path`/this/is/(scot %tas 'test')/path/this/is/test/path> /~
Strings with Interpolation
Text string with interpolation.
Syntax
A $tape
"abcdefg"
"abc{(weld "lmnop" "xyz")}defg"
> "abcdefg""abcdefg"> "abc{(weld "lmnop" "xyz")}defg""abclmnopxyzdefg"> (ream '"abcdefg"')[%knit p=~[97 98 99 100 101 102 103]]
AST
[%knit p=(list woof)]
Produces
A tape.
Examples
String:
> "hello, world.""hello, world."
String with interpolation:
> =+(planet="world" "hello, {planet}.")"hello, world."
String with interpolated prettyprinting:
> =+(planet=%world "hello, {<planet>}.")"hello, %world."
Warm Atoms
A constant, warm atom.
Syntax
A table of examples:
Aura Meaning Example Literal Syntax-------------------------------------------------------------------------@ empty aura@c UTF-32 ~-~45fed@d date@da absolute date ~2018.5.14..22.31.46..1435@dr relative date (ie, timespan) ~h5.m30.s12@f Loobean (for compiler, not castable) &@i Internet address@if IPv4 address .195.198.143.90@is IPv6 address .0.0.0.0.0.1c.c3c6.8f5a@n nil (for compiler, not castable) ~@p phonemic base (ship name) ~sorreg-namtyv@q phonemic base, unscrambled .~litsyn-polbel@r IEEE-754 floating-point@rh half precision (16 bits) .~~3.14@rs single precision (32 bits) .6.022141e23@rd double precision (64 bits) .~6.02214085774e23@rq quad precision (128 bits) .~~~6.02214085774e23@s signed integer, sign bit low@sb signed binary --0b11.1000@sd signed decimal --1.000.056@sv signed base32 -0v1df64.49beg@sw signed base64 --0wbnC.8haTg@sx signed hexadecimal -0x5f5.e138@t UTF-8 text (cord) 'howdy'@ta ASCII text (knot) ~.howdy@tas ASCII text symbol (term) %howdy@u unsigned integer@ub unsigned binary 0b11.1000@ud unsigned decimal 1.000.056@uv unsigned base32 0v1df64.49beg@uw unsigned base64 0wbnC.8haTg@ux unsigned hexadecimal 0x5f5.e138
AST
[%sand p=term q=*]
Discussion
A 'warm' atom is one whose type is inferred to be general, i.e., not just a single atom type.
> `@`1212> `%12`12nest-fail
Produces
A warm (variable) atom q with aura p. Use the Hoon compiler parser function ream to take a closer look:
> (ream '12')[%sand p=%ud q=12]> (ream '\'Hello!\'')[%sand p=%t q=36.762.444.129.608]