feat(graphing): automatically select distinct function names, e.g. f(x), g(x), ...

app/src/main/java/net/youapps/calcyou/data/graphing/Defaults.kt

@@ -45,6 +45,7 @@ object Defaults {
     )
     val defaultVarNameChars: Set<Char> =
         "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_$".toCharArray().toSet()
+    val defaultFuncNameChars: List<Char> = "fghijklmnopqrstuvw".toList()
 
     fun getDefaultGenericFunctions(): Map<String, EvalFunctionBlock> {
         return mapOf(

app/src/main/java/net/youapps/calcyou/data/graphing/EvalConfig.kt

@@ -82,6 +82,5 @@ class EvalConfiguration(
         this.varNameChars = Defaults.defaultVarNameChars
         this.genericConstants = Defaults.defaultGenericConstants.toMutableMap()
         this.genericFunctions = Defaults.getDefaultGenericFunctions().toMutableMap()
-
     }
 }

app/src/main/java/net/youapps/calcyou/data/graphing/Function.kt

@@ -5,14 +5,15 @@ import androidx.compose.ui.graphics.Color
 class Function(
     val expression: String,
     val color: Color,
+    val name: String,
     val function: (Float) -> Float?
 ) {
 
     companion object {
-        fun create(expression: String, color: Color): Function {
+        fun create(expression: String, color: Color, functionName: String): Function {
             val compiled: CompiledExpression = Evaluator.compile(expression)
             return Function(
-                expression, color
+                expression, color, functionName
             ) { value ->
                 compiled.execute("x" to value.toDouble())?.toFloat()
             }

app/src/main/java/net/youapps/calcyou/ui/components/AddNewFunctionDialog.kt

@@ -39,20 +39,22 @@ import net.youapps.calcyou.viewmodels.GraphViewModel
 @Composable
 fun AddNewFunctionDialog(
     graphViewModel: GraphViewModel,
+    functionName: String,
     initialExpression: String,
     initialColor: Color,
     onDismissRequest: () -> Unit
 ) {
     Dialog(onDismissRequest) {
         DialogContent(
             onConfirm = { expression, color ->
-                graphViewModel.addFunction(expression, color)
+                graphViewModel.addFunction(expression, color, functionName)
                 onDismissRequest()
             },
             onCancel = onDismissRequest,
             checkExpression = graphViewModel::checkExpression,
             isError = graphViewModel.isError,
             errorMessage = graphViewModel.errorText,
+            functionName = functionName,
             initialExpression = initialExpression,
             initialColor = initialColor
         )
@@ -67,6 +69,7 @@ private fun DialogContent(
     checkExpression: (String) -> Unit,
     isError: Boolean,
     errorMessage: String,
+    functionName: String,
     initialExpression: String = "",
     initialColor: Color = rainbowColors.first(),
 ) {
@@ -92,7 +95,7 @@ private fun DialogContent(
                 isError = isError,
                 prefix = {
                     Text(
-                        text = "f(x) = ", style = TextStyle(
+                        text = "${functionName}(x) = ", style = TextStyle(
                             fontFamily = FontFamily.Serif,
                             fontWeight = FontWeight.Medium,
                             fontSize = MaterialTheme.typography.bodyLarge.fontSize,
@@ -149,6 +152,7 @@ private fun DialogContentPreview() {
         onCancel = {},
         checkExpression = {},
         isError = true,
-        errorMessage = "Invalid token at index 0"
+        errorMessage = "Invalid token at index 0",
+        functionName = "f"
     )
 }

app/src/main/java/net/youapps/calcyou/ui/screens/graphing/GraphingScreen.kt

@@ -33,6 +33,7 @@ import androidx.compose.ui.text.font.FontStyle
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
 import androidx.lifecycle.viewmodel.compose.viewModel
+import net.youapps.calcyou.data.graphing.Defaults
 import net.youapps.calcyou.data.graphing.Function
 import net.youapps.calcyou.ui.components.AddNewFunctionDialog
 import net.youapps.calcyou.viewmodels.GraphViewModel
@@ -82,6 +83,7 @@ fun GraphingScreen(graphViewModel: GraphViewModel = viewModel()) {
                 graphViewModel.updateSelectedFunction(-1)
                 showAddFunctionDialog = false
             },
+            functionName = remember(graphViewModel.selectedFunctionIndex) { graphViewModel.functionName },
             initialColor =
             remember(graphViewModel.selectedFunctionIndex) { graphViewModel.functionColor },
             initialExpression =
@@ -100,6 +102,7 @@ fun FunctionList(
     Column(modifier = modifier) {
         functions.forEachIndexed { index, function ->
             FunctionRow(
+                functionName = function.name,
                 text = function.expression,
                 color = function.color,
                 onClick = { onClickFunction(index) },
@@ -112,7 +115,7 @@ fun FunctionList(
 }
 
 @Composable
-fun FunctionRow(text: String, color: Color, onClick: () -> Unit, onClickRemove: () -> Unit) {
+fun FunctionRow(functionName: String, text: String, color: Color, onClick: () -> Unit, onClickRemove: () -> Unit) {
     Row(
         modifier = Modifier
             .fillMaxWidth()
@@ -122,7 +125,7 @@ fun FunctionRow(text: String, color: Color, onClick: () -> Unit, onClickRemove:
     ) {
 
         Text(
-            text = "f(x) = ", style = TextStyle(
+            text = "${functionName}(x) = ", style = TextStyle(
                 fontFamily = FontFamily.Serif,
                 fontWeight = FontWeight.Bold,
                 fontSize = MaterialTheme.typography.titleMedium.fontSize,

app/src/main/java/net/youapps/calcyou/viewmodels/GraphViewModel.kt

@@ -11,14 +11,16 @@ import androidx.compose.runtime.setValue
 import androidx.compose.ui.graphics.Color
 import androidx.lifecycle.AndroidViewModel
 import net.youapps.calcyou.R
+import net.youapps.calcyou.data.graphing.Defaults
 import net.youapps.calcyou.data.graphing.Evaluator
 import net.youapps.calcyou.data.graphing.Function
 import net.youapps.calcyou.data.graphing.Window
+import net.youapps.calcyou.ui.components.rainbowColors
 import java.text.ParseException
 import kotlin.random.Random
 
 class GraphViewModel(private val application: Application) : AndroidViewModel(application) {
-    val context: Context
+    private val context: Context
         get() = application.applicationContext
     var window by mutableStateOf(Window(), neverEqualPolicy())
     val functions = mutableStateListOf<Function>()
@@ -30,17 +32,24 @@ class GraphViewModel(private val application: Application) : AndroidViewModel(ap
 
     var selectedFunctionIndex by mutableIntStateOf(-1)
         private set
-    var functionColor by mutableStateOf(Color.Red)
+    var functionName by mutableStateOf(Defaults.defaultFuncNameChars.first().toString())
+
+    var functionColor by mutableStateOf(rainbowColors.first())
 
     var expression by mutableStateOf("")
 
     fun updateSelectedFunction(index: Int) {
         selectedFunctionIndex = index
         if (index == -1) {
             expression = ""
+            functionName = Defaults.defaultFuncNameChars[
+                functions.size % Defaults.defaultFuncNameChars.size
+            ].toString()
+            functionColor = rainbowColors[functions.size % rainbowColors.size]
             return
         }
         val function = functions[index]
+        functionName = function.name
         functionColor = function.color
         expression = function.expression
     }
@@ -64,13 +73,13 @@ class GraphViewModel(private val application: Application) : AndroidViewModel(ap
         }
     }
 
-    fun addFunction(expression: String, color: Color) {
+    fun addFunction(expression: String, color: Color, functionName: String) {
         if (selectedFunctionIndex != -1) {
-            functions[selectedFunctionIndex] = Function.create(expression, color)
+            functions[selectedFunctionIndex] = Function.create(expression, color, functionName)
             updateSelectedFunction(-1)
             return
         }
-        functions.add(Function.create(expression, color))
+        functions.add(Function.create(expression, color, functionName))
     }
 
     fun removeFunction(index: Int) {