feat: Add rounding to language specification

docs/language/common/functions.md

@@ -67,6 +67,11 @@ function taxes(name: String): List GroupedBy XYZ_id {...}
 
 In this example the return value of the function is grouped by XYZ_id.
 
+## Rounding
+
+The [rounding modifier][rounding] can be added to a function of a single [timespan][Validity] in the function to define the rounding direction for the return value. More detailed Documentation can be found in the [rounding modifier][rounding] section.
+
+
 [Parameters]: parameters.md
 [Type]: types.md
 [id]: modifier.md#id
@@ -77,3 +82,4 @@ In this example the return value of the function is grouped by XYZ_id.
 [modifier timespan]: modifier.md#timespan
 [Statement]: statements.md
 [Aggregations]: aggregations.md
+[rounding]: modifier.md#rounding

docs/language/common/modifier.md

@@ -57,7 +57,25 @@ var x = per week f()
 y = per year salary
 ```
 
+## Rounding
+
+[Functions][Functions] can return a rounded value. The direction in which the value should be rounded can be specified for the whole function of for specific [timespans][Timespans].
+
+```ttsl
+# For the whole function:
+function f() round:ceil : Int {...}
+
+# For a specific timespan:
+from 2001-01-01: ceil {}
+```
+
+The options for rounding are following:
+- ceil: round up
+- floor: round down
+- round: round depending on the following
+
 [Constants]:constants.md
 [Data]:data.md
 [Functions]:functions.md
 [Aggregation]: aggregations.md
+[Timespans]: validity.md

packages/ttsl-lang/src/language/grammar/safe-ds.langium

@@ -307,6 +307,7 @@ TslEnumVariant returns TslEnumVariant:
 interface TslFunction extends TslCallable, TslClassMember, TslModuleMember {
     isID: boolean
     typeParameterList?: TslTypeParameterList
+    rounding?: TslRounding
     resultList?: TslResultList
     timeunit?: TslTimeunit
     groupedBy?: TslGroupedBy
@@ -322,23 +323,22 @@ fragment TslFunctionFragment:
     name=ID
     typeParameterList=TslTypeParameterList?
     parameterList=TslParameterList
+    ('round' rounding=TslRounding)?
     resultList=TslResultList?
     (groupedBy=TslGroupedBy)?
     constraintList=TslConstraintList?
     body=TslFunctionBlock
 ;
 
 interface TslFunctionBlock extends TslBlock{
-    timespans: TslTimespan[]
+    timespanStatement: TslTimespanStatement[]
 }
 
 TslFunctionBlock returns TslFunctionBlock:
-    {TslFunctionBlock} 
-    '{' ( statements+=TslStatement* 
-    | timespans+=TslTimespan 
-    '{' ( timespans+=TslTimespan statements+=TslStatement 
-    | statements+=TslStatement)* 
-    '}')* '}'
+    {TslFunctionBlock}
+    '{' ( timespanStatement+=TslTimespanStatement
+    | statements+=TslStatement)*
+    '}'
 ;
 
 interface TslConstant extends TslModuleMember {
@@ -1019,7 +1019,7 @@ TslTemplateStringEnd returns TslExpression:
 interface TslModifier extends TslObject{}
 
 interface TslVisibility extends TslModifier{
-    isPublic?: boolean 
+    isPublic?: boolean
     isPackageprivate?: boolean
     isPrivate?: boolean
 }
@@ -1044,6 +1044,14 @@ TslGroupedBy returns TslGroupedBy:
     'groupedBy' id=TslExpression
 ;
 
+interface TslRounding extends TslModifier{
+    rounding: string
+}
+
+TslRounding returns TslRounding:
+    ':' rounding=('round'|'ceil'|'floor')
+;
+
 // -----------------------------------------------------------------------------
 // Timespan
 // -----------------------------------------------------------------------------
@@ -1057,6 +1065,16 @@ TslTimespan returns TslTimespan:
     ('from' start=TslDate)? ('to' end=TslDate)?
 ;
 
+interface TslTimespanStatement extends TslBlock, TslStatement{
+    timespan: TslTimespan
+    rounding?: TslRounding
+    block: TslFunctionBlock
+}
+
+TslTimespanStatement returns TslTimespanStatement:
+    timespan=TslTimespan (rounding=TslRounding)? '{' block=TslFunctionBlock '}'
+;
+
 // -----------------------------------------------------------------------------
 // Types
 // -----------------------------------------------------------------------------