Module otpcl_core

Description
Data Types
Function Index
Function Details

Core OTPCL commands.

Description

Core OTPCL commands. These commands are technically optional, but leaving them out (i.e. in a custom interpreter state) can create some rather peculiar results, in particular since this is where basic commands like return and | live (yes, the OTPCL standard pipe is internally an ordinary command, so you can call it on its own; you can also define your own pipe-commands, as detailed below).

Data Types

funs()

funs() = map()

state()

state() = {funs(), vars()}

vars()

vars() = map()

Function Index

'\|'/2	Inline command chaining operator.
return/2	Sets `$RETVAL` in the given state.

Function Details

'|'/2

'|'(Args::[any() | [any()]], State::state()) -> {any(), state()}

Inline command chaining operator. Takes the result of the preceding command (stored in $RETVAL) and passes it as the first argument to the named command (the rest of the arguments passed being passed through as additional arguments to the named command).

OTPCL's parser treats any "free" instance of a pipe character (i.e. unescaped and not already part of some other word) as a command terminator, so OTPCL will interpret a line like foo | bar | baz as equivalent to separately calling foo, | bar, and | baz (which would in turn be equivalent to baz [bar [foo]]). This means that it's possible to define custom commands with pipe-like behavior, and rather simply, too; for example, to define a |! command that sends the result of a command to a process:

 '|!'([Pid], State) ->
     {RetVal, State} = otpcl_meta:get(['RETVAL', State),
     Pid ! RetVal,
     {ok, State}.

Assuming the above function is tied to a command name somehow, one could then call foo bar baz |! $pid to send the result of the command foo bar baz as a message to the process identified via $pid.

return/2

return(Args::any(), State::state()) -> {any(), state()}

Sets $RETVAL in the given state. $RETVAL will be set to one of ok (if passed an empty list), the list element (if passed a single-element list) or the given return value as-is (if passed literally anything else). Because $RETVAL is an ordinary OTPCL variable, it's possible to write functions/commands that read it, allowing for, say, chained operations on an item (this is, notably, how OTPCL's pipe functionality works; more on that in the documentation for '|'/2).

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