Generator Language

conditional root rule

Generates a root node in the output model. Applied only one time (max) during a single generation step.

condition function (optional), missing condition function is equivalent to a function always returning true.

root template (ref)

root mapping rule

Generates a root node in the output model.

concept- applicable concept (concept of the input node)
inheritors- if true then the rule is applicable to the specified concept and all its sub-concepts. If false (default) then the sub-concepts are not applicable.
condition function (optional) - see conditional root rule above.
keep input root- if false then the input root node (if it's a root node) will be dropped. If true then input root will be copied to the output model.

root template (ref)

weaving rule

Allows to insert additional child nodes into the output model. Weaving rules are processed at the end of a generation micro-step just before map_src and reference resolving. The rule is applied on each input node of the specified concept. The parent node for insertion should be provided by the context function.

concept- same as above
inheritors- same as above
condition function (optional) - same as above

• external template (ref)

• weave-each 

• context - function that computes the (parent) output node into which the output node(s) generated by this rule will be inserted.

• anchor (available in Inspector) - specifies a node within the context collection, in front of which the nodes should be inserted, null means insert at the end of the collection

reduction rule

Transforms the input node while this node is being copied to the output model.

concept- same as above
inheritors- same as above
condition function (optional) - same as above

• external template (ref)

• in-line template

• in-line switch

• dismiss top rule

• abandon input

pattern rule

Transforms the input node, which matches the pattern.

pattern- pattern expression
condition function (optional) - same as above

• external template (ref)

• in-line template

• dismiss top rule

• abandon input

abandon root rule

Allows to drop an input root node which otherwise would be copied into the output model.

applicable concept ( including all its sub-concepts)
condition function (optional) - same as above

n/a

n/a

Attribute is not copied when the rule matches

root template (ref)

• conditional root rule

• (root) mapping rule

Applies the root template

external template (ref)

• weaving rule

• reduction rule

• pattern rule

Applies an external template. Parameters should be passed if required, they can be one of:

• pattern captured variable (starting with # sign)

• integer or string literal

• null, true, false

• query function

weave-each

weaving rule

Applies an external template to a set of input nodes.
Weave-each consequence consists of:

• foreach function - returns a sequence of input nodes

• reference on an external template

in-line template

• reduction rule

• pattern rule

Applies the template code which is written right here.

in-line switch

reduction rule

Consists of set of conditional cases and a default case.
Each case specify a consequence, which can be one of:

• external template (ref)

• in-line template

• dismiss top rule

• abandon input

dismiss top rule

• reduction rule

• pattern rule

Drops all reduction-transformations up to the point where this sequence of transformations has been initiated by an attempt to copy the input node to the output model. The input node will be copied 'as is' (unless some other reduction rules are applicable). The user can also specify an error, warning or an information message.

abandon input

• reduction rule

• pattern rule

Prevents the input node from being copied into the output model.

Property macro

Computes the value of a property.

value function:

• return type - string, boolean or int - depending on the property type.

• parameters - standard + templateValue- value in the template code wrapped by the macro.

Reference macro

Computes the referent node in the output model.
Normally executed at the end of a generation micro-step, when the output model (tree) is already constructed.
Can also be executed earlier, if the user code is trying to obtain the target of the reference.

Reference macro supports  SNodeReference  as specification of a new target. With that, templates don't need access to a target's node model the moment they are applied. 

referent function:

• return type

  • node (type depends on the reference link declaration)

  • SNodeReference

  • string identifying the target node.

• parameters - standard + outputNode- source of the reference link (in the output model).

IF

The wrapped template code is applied only if the condition is true. Otherwise the template code is ignored and an 'alternative consequence' (if any) is applied.

condition function
alternative consequence (optional) - any of:

• external template (ref)

• in-line template

• abandon input

• dismiss top rule

LOOP

Computes new input nodes and applies the wrapped template to each of them. It also introduces a LOOP variable that becomes available for queries on macros that are attached to nodes wrapped by the LOOP macro. The LOOP variable gives access to the node that is currently being processed by the LOOP macro. For example, LOOP.index holds the index of the current node in the iteration, LOOP.inputNode holds the current node itself.

mapped nodes function

INCLUDE

The wrapped template code is ignored (it only serves as an anchor for the INCLUDE-macro), a reusable external template will be used instead.

Null input makes INCLUDE effectively a no-op.

mapped node function (optional)
include template- reference to a reusable external template

CALL

Invokes template and replaces wrapped template code with the result of template invocation. Supports templates with parameters.

Null input node is tolerated, and the template is ignored altogether in this case, i.e. CALL yields empty collection of nodes as a result when input/mapped node is null.

mapped node function (optional)
call template- reference to a reusable external template

argument- one of

• pattern captured variable

• integer or string literal

• null, true, false

• query function

SWITCH

Provides a way to many alternative transformations in the given place in the template code.
The wrapped template code is applied, if none of switch cases is applicable and no default consequence is specified in #template switch.

For null input node, SWITCH may react with a message (specified along with its rules), anchor template node is ignored, and SWITCH macro yields no results.

mapped node function (optional)
template switch- reference to a template switch

CALL-SITE

Facilitates insertion of a node attributed with a SWITCH/CALL macro in a designated place of the invoked template. In the scenarios when the node wrapped with the SWITCH/CALL macro is relevant in the invoked template/switch, this macro attaches it as a 'call site node'. The node is in such cases processed as a regular template (including potential macros) and the outcome is then supplied to the invoked template/switch as an implicit argument, ready to get inserted into desired location.

Templates and switch declarations have a flag (toggled by intention) that indicates that they like to use the call site node. It's an error to use the $CALL-SITE$ macro inside a template/switch that didn't flag the need to get call site. There's no need to specify any explicit argument in CALL/SWITCH, The MPS generator notices that a template/switch needs its call site and in such cases evaluates further templates (including the macros) prior to processing it. This functionality comes handy in scenarios like conditional type casts (IF needCast (Type) expression ELSE expression) or conversions when there are multiple sources of expression that may serve as an input, and it's therefore impractical to have dedicated switch/template for each case:
switch { case Double : Double.valueOf(expression); case Integer : Integer.valueOf(expression, 16); ... }

COPY-SRC

Copies an input node to the output model. The wrapped template code is ignored.

mapped node function - computes the input node to be copied.

COPY-SRCL

Copies input nodes to the output model. The wrapped template code is ignored.
Can be used only for children with multiple aggregation cardinality.

mapped nodes function - computes the input nodes to be copied.

MAP-SRC

Multifunctional macro, can be used for:

• marking a template code with a mapping label;

• replacing the current input node with a new one;

• perform a non-template based transformation;

• accessing the output node for some reason.
  The MAP-SRC macro is executed at the end of a generator micro-step - after all node- and property-macros, but before any reference-macro is run.

mapped node function (optional)
mapping func function (optional) - performs non-template based transformation.
If defined then the wrapped template code will be ignored.
Parameters: standard + parentOutputNode- parent node in the output model.
post-processing function (optional) - give access to the output node.
Parameters: standard + outputNode

MAP-SRCL

Same as MAP-SRC but can handle many new input nodes (similar to the LOOP-macro)

mapped nodes function
mapping func function (optional)
post-processing function (optional)

WEAVE

Allows to insert additional child nodes into the output model in a similar way Weaving rules are used. The node wrapped in the WEAVE macro  (or provided by the use input  function) will have the supplied template applied to it and the generated nodes will be inserted.

use input  a function returning a collection of nodes to apply the macro to
weave  reference to a template to weave into the nodes supplied as the input

VAR

Introduces one or more named values into the generator context, which can then be obtained from the genContext object. The stored variables are read-only and live in the generator context within the scope of the VAR macro.

Each variable has the following parameters:
type the optional BaseLanguage type of the stored value, defaults to the type inferred from the value function.
value function - returns the value to store in the variable.

modifies model

only available if script kind = pre-process input model
If set true and the input model is the original input model, then MPS will create a transient input model before applying the script.
If set false but the script tries to modify the input model, then MPS will issue an error.

genContext

The generation context to give access to transient/session or step objects.

invocation context

Operation context (jetbrains.mps.smodel.IOperationContext java interface) associated with the module - the owner of the original input model