Identifiers

Flix has several types of identifiers:

  • Uppercase name: An identifier that starts with an uppercase letter followed by any number of uppercase and lowercase letters, underscore, and exclamation mark (A…Z, a…z, _, !).
    • e.g. String, ALL_UPPER, Shriek!
    • Can be used to name: namespaces, annotations, traits, effects, predicates (within datalog), tags (within enums), types
  • Lowercase name: An identifier that starts with aa lowercase letter followed by any number of uppercase and lowercase letters, underscore, and exclamation mark (A…Z, a…z, _, !).
    • e.g. anIdentifier, x, this_and_that
    • Can be used to name: annotations, attributes (within datalog), functions, labels (within records), variables
  • Greek name: An identifier consisting of any combination of letters from the Greek alphabet (the unicode range U+0370 to U+03FF).
    • e.g. Χαίρετε, αναγνωριστικό
    • Can be used to name: functions, variables
  • Math name: An identifier consisting of any combination of math symbols (the unicode range U+2190 to U+22FF).
    • e.g. ⊆, √, ⊙
    • Can be used to name: functions, variables
  • Operator name: An identifier of minimum length 2 consisting of any combination of +, -, *, <, >, =, !, &, |, ^, and $.
    • e.g. >==>, <*>
    • Can be used to name: functions

Note that greek letters, math symbols, and operator letters cannot be combined within a single identifier.

Reserved Identifiers

The following are reserved by Flix and cannot be redefined within user code:

!=, **, .., ::, :=, <-, <=, ==, =>, >=, or, &&&, <+>, <<<, <=>, >>>, ???, ^^^, and, mod, not, |||, ~~~, $DEFAULT$, *, +, -, /, :, <, >, @, Absent, Bool, Impure, Nil, Predicate, Present, Pure, Read, RecordRow, Region, SchemaRow, Type, Write, alias, case, catch, chan, class, def, deref, else, enum, false, fix, force, if, import, inline, instance, into, lat, law, lawful, lazy, let, match, mod, null, opaque, pub, redef, ref, region, reify, reifyBool, reifyEff, reifyType, rel, sealed, set, spawn, Static, trait, true, type, use, where, with, discard, object, choose, solve, inject, project