public class AstFrame extends AstRoot
Modifier and Type | Method and Description |
---|---|
java.lang.String |
description()
Return the detailed description (help) for what this language construct
does or how it is supposed to be used.
|
java.lang.String |
example()
Return an example of how this Ast construct ought to be used.
|
Val |
exec(Env env)
"Execute" this AST expression, and return the result.
|
java.lang.String |
str()
String representation of this Ast object in the Rapids language.
|
asBytes, clone, copyOver, frozenType, read, readExternal, readJSON, reloadFromBytes, toJsonString, write, writeExternal, writeJSON
public AstFrame()
public AstFrame(Frame fr)
public java.lang.String str()
AstRoot
AstPrimitive
s this is the name of the function; for
AstParameter
s this is either the name of the variable, or the
value of the numeric constant that the parameter represents. For more
complicated constructs such as AstExec
or AstFunction
this method should return those objects as a Rapids string.public java.lang.String example()
AstRoot
Return an example of how this Ast construct ought to be used. This
method is used to build documentation for the Rapids language. It is
different from AstRoot.str()
, in particular it must provide a valid
example even in a static context. For example, an AstStr
may
return "Hello, world!"
as an example. At the same time,
for different AstPrimitive
s this method should generally provide
a typical example of how that function is to be used.
Return null
to indicate that the object should not be
included in the documentation.
public java.lang.String description()
AstRoot
Return the detailed description (help) for what this language construct
does or how it is supposed to be used. This method is used in conjunction
with AstRoot.example()
to build the documentation of the Rapids
language.
If you need to include any formatting, then please use Markup language. Although it is up to the client to support it, Markup is one of the simplest and easiest alternatives.
Return null
to indicate that the object should not be
included in the documentation.
description
in class AstRoot
public Val exec(Env env)
AstRoot
"Execute" this AST expression, and return the result. For different ASTs this may have different interpretation. For example, consider this Rapids expression:
(mean frame True False)
It will be parsed into the following structure:
AstExec() instance with _asts = [AstMean() singleton instance, new AstId(frame), AstConst.TRUE, AstConst.FALSE]
Execution of AstExec
will execute its first argument, _asts[0],
verify that it produces a function (ValFun
), then call
AstPrimitive.apply(Env, Env.StackHelp, AstRoot[])
on that function
passing down the list of _asts arguments.
The AstMean
class will in turn execute all its arguments,
where execution of AstId
fetches the referred symbol from the
environment, and execution of AstConst
returns the value of that
constant.
Certain other functions may choose not to evaluate all their arguments (for example boolean expressions providing short-circuit evaluation).