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Overview
Agena offers various flow control
facilities such as
- if/then/elif/else conditions,
- case of/else conditions
similar to C's switch/case statements,
- is operator to return
alternative values,
- numerical for/from/to/by loops where
start, stop, and step values are optional, and automatic round-off error correction of iteration variables,
- combined numerical for/while loops,
- for/in loops over
strings and complex data
structures,
- while and do/as loops similar to
Modula's while and repeat/until not() iterators,
- a skip statement to
prematurely trigger
the next iteration of a loop,
- a break statement
to prematurely leave a loop,
- data type validation with the try/else statement and the optional double colon facility in parameter lists.
Data
types provided are:
- rational and complex numbers, with
extensions such as infinity
and undefined,
- strings,
- Booleans such as true, false, and fail,
- the null value meaning
'nothing',
- multi-purpose tables
implemented as associative arrays to hold any kind of data, taken from
Lua,
- Cantor sets as collections of unique items,
- sequences, i.e. vectors, to internally store items
in strict
sequential order,
- pairs to hold two values
or pass arguments in any order to procedures,
- user-defined
types for sequences, tables, and pairs to allow for special-purpose handling,
- threads, userdata, and
lightuserdata inherited from Lua.
For
performance, most basic operations on these types were built into the
Agena kernel.
Procedures
with full lexical scoping are supported, as well, and provide
the following extensions:
- the <<
(args) ->
expression >>
syntax to easily define simple functions,
- remember tables to conduct recursion at high speed and at low memory consumption,
- remember tables for fast access to predefined results,
- user-defined
types,
- the nargs system
variable which holds the number of arguments actually passed to a
procedure,
- metamethods inherited from Lua to define
operations for tables, sets, sequences, and pairs,
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