Merge pull request #632 from jansule/interpolate

feat: add interpolate function

functions.ts

@@ -25,6 +25,7 @@ Fcos |
 Fdiv |
 Fexp |
 Ffloor |
+Finterpolate |
 Flog |
 Fmax |
 Fmin |
@@ -84,8 +85,7 @@ FparseBoolean |
 FstrEndsWith |
 FstrEqualsIgnoreCase |
 FstrMatches |
-FstrStartsWith |
-FtoBoolean;
+FstrStartsWith;
 
 export type GeoStylerUnknownFunction = Fcase | Fstep | Fproperty;
 
@@ -740,17 +740,6 @@ export interface Ftan extends FunctionCall<number> {
   ];
 };
 
-/**
- * Converts an unknown value to boolean
- */
-export interface FtoBoolean extends FunctionCall<boolean> {
-  name: 'toBoolean';
-  args: [
-    Expression<unknown>
-  ];
-};
-
-
 /**
  * Converts an angle expressed in radians into degrees
  */
@@ -790,3 +779,34 @@ export interface FtoString extends FunctionCall<string> {
     Expression<unknown>
   ];
 };
+
+export type FInterpolateTypeLinear = {
+  name: 'linear';
+};
+
+export type FInterpolateType = FInterpolateTypeLinear;
+
+export type FInterpolateParameter = {
+  stop: Expression<number>;
+  value: Expression<PropertyType>;
+};
+
+/**
+ * Textual representation of a interpolate function.
+ * argument[0] is the interpolation type.
+ * argument[1] is the input value.
+ * argument[2] - argument[args.length] are objects with 'stop' and 'value'.
+ *
+ * Will produce continuous results by interpolating between pairs
+ * of FInterpolateParamters.
+ */
+export interface Finterpolate extends FunctionCall<number> {
+  name: 'interpolate';
+  args: [
+    FInterpolateType,
+    Expression<number>,
+    FInterpolateParameter,
+    FInterpolateParameter,
+    ...FInterpolateParameter[]
+  ];
+};

typeguards.ts

@@ -203,6 +203,7 @@ export const isGeoStylerNumberFunction = (got: any): got is GeoStylerNumberFunct
     'div',
     'exp',
     'floor',
+    'interpolate',
     'log',
     'max',
     'min',
@@ -221,6 +222,7 @@ export const isGeoStylerNumberFunction = (got: any): got is GeoStylerNumberFunct
     'sub',
     'tan',
     'toDegrees',
+    'toNumber',
     'toRadians'
   ];
   return functionNames.includes(got?.name);
@@ -238,6 +240,7 @@ export const isGeoStylerStringFunction = (got: any): got is GeoStylerStringFunct
     'strSubstring',
     'strSubstringStart',
     'strToLowerCase',
+    'strToString',
     'strToUpperCase',
     'strTrim'
   ];
@@ -271,6 +274,7 @@ export const isGeoStylerUnknownFunction = (got: any): got is GeoStylerUnknownFun
   const functionNames: GeoStylerUnknownFunction['name'][] = [
     'case',
     'property',
+    'step'
   ];
   return functionNames.includes(got?.name);
 };