feat(otherwise): Added otherwise expression for null value handling

ast.json

@@ -1 +1 @@
-{"type":"Program","body":[{"type":"ObjectDeclaration","identifier":"person","count":30,"body":[{"type":"VariableDeclaration","variableType":"Const","identifier":"speed","value":{"type":"NumericLiteral","value":4}},{"type":"VariableDeclaration","variableType":"Property","identifier":"angle","value":{"type":"BinaryExpression","left":{"type":"Identifier","identifier":"angle"},"right":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"choice"},"args":[{"type":"UnaryExpression","operator":"-","value":{"type":"NumericLiteral","value":0.1}},{"type":"NumericLiteral","value":0.1}]},"operator":"+"},"default":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"random"},"args":[{"type":"NumericLiteral","value":0},{"type":"BinaryExpression","left":{"type":"NumericLiteral","value":2},"right":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"pi"},"args":[]},"operator":"*"}]}},{"type":"VariableDeclaration","variableType":"Property","identifier":"shouldStay","value":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"prob"},"args":[{"type":"NumericLiteral","value":0.5}]}},{"type":"VariableDeclaration","variableType":"Property","identifier":"xNew","value":{"type":"BinaryExpression","left":{"type":"BinaryExpression","left":{"type":"Identifier","identifier":"x"},"right":{"type":"BinaryExpression","left":{"type":"Identifier","identifier":"speed"},"right":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"cos"},"args":[{"type":"Identifier","identifier":"angle"}]},"operator":"*"},"operator":"+"},"right":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"width"},"args":[]},"operator":"%"},"default":{"type":"NumericLiteral","value":0}},{"type":"VariableDeclaration","variableType":"Property","identifier":"yNew","value":{"type":"BinaryExpression","left":{"type":"BinaryExpression","left":{"type":"Identifier","identifier":"y"},"right":{"type":"BinaryExpression","left":{"type":"Identifier","identifier":"speed"},"right":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"sin"},"args":[{"type":"Identifier","identifier":"angle"}]},"operator":"*"},"operator":"+"},"right":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"height"},"args":[]},"operator":"%"},"default":{"type":"NumericLiteral","value":0}},{"type":"VariableDeclaration","variableType":"Property","identifier":"x","value":{"type":"ConditionalExpression","condition":{"type":"Identifier","identifier":"shouldStay"},"consequent":{"type":"Identifier","identifier":"x"},"alternate":{"type":"Identifier","identifier":"xNew"}},"default":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"random"},"args":[{"type":"NumericLiteral","value":50},{"type":"BinaryExpression","left":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"width"},"args":[]},"right":{"type":"NumericLiteral","value":50},"operator":"-"}]}},{"type":"VariableDeclaration","variableType":"Property","identifier":"y","value":{"type":"ConditionalExpression","condition":{"type":"Identifier","identifier":"shouldStay"},"consequent":{"type":"Identifier","identifier":"y"},"alternate":{"type":"Identifier","identifier":"yNew"}},"default":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"random"},"args":[{"type":"NumericLiteral","value":50},{"type":"BinaryExpression","left":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"height"},"args":[]},"right":{"type":"NumericLiteral","value":50},"operator":"-"}]}},{"type":"VariableDeclaration","variableType":"Const","identifier":"distance","value":{"type":"NumericLiteral","value":20}},{"type":"VariableDeclaration","variableType":"Property","identifier":"people","value":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"agents"},"args":[{"type":"Identifier","identifier":"person"}]}},{"type":"VariableDeclaration","variableType":"Property","identifier":"closePeople","value":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"filter"},"args":[{"type":"LambdaExpression","base":{"type":"Identifier","identifier":"people"},"param":"p","value":{"type":"BinaryExpression","left":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"sqrt"},"args":[{"type":"BinaryExpression","left":{"type":"BinaryExpression","left":{"type":"BinaryExpression","left":{"type":"MemberExpression","caller":{"type":"Identifier","identifier":"p"},"value":{"type":"Identifier","identifier":"x"}},"right":{"type":"Identifier","identifier":"x"},"operator":"-"},"right":{"type":"BinaryExpression","left":{"type":"MemberExpression","caller":{"type":"Identifier","identifier":"p"},"value":{"type":"Identifier","identifier":"x"}},"right":{"type":"Identifier","identifier":"x"},"operator":"-"},"operator":"*"},"right":{"type":"BinaryExpression","left":{"type":"BinaryExpression","left":{"type":"MemberExpression","caller":{"type":"Identifier","identifier":"p"},"value":{"type":"Identifier","identifier":"y"}},"right":{"type":"Identifier","identifier":"y"},"operator":"-"},"right":{"type":"BinaryExpression","left":{"type":"MemberExpression","caller":{"type":"Identifier","identifier":"p"},"value":{"type":"Identifier","identifier":"y"}},"right":{"type":"Identifier","identifier":"y"},"operator":"-"},"operator":"*"},"operator":"+"}]},"right":{"type":"Identifier","identifier":"distance"},"operator":"<="}}]}},{"type":"VariableDeclaration","variableType":"Property","identifier":"closeInfected","value":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"filter"},"args":[{"type":"LambdaExpression","base":{"type":"Identifier","identifier":"closePeople"},"param":"c","value":{"type":"BinaryExpression","left":{"type":"MemberExpression","caller":{"type":"Identifier","identifier":"c"},"value":{"type":"Identifier","identifier":"infected"}},"right":{"type":"BooleanLiteral","value":true},"operator":"=="}}]}},{"type":"VariableDeclaration","variableType":"Const","identifier":"timespan","value":{"type":"NumericLiteral","value":200}},{"type":"VariableDeclaration","variableType":"Property","identifier":"remaining","value":{"type":"ConditionalExpression","condition":{"type":"Identifier","identifier":"infected"},"consequent":{"type":"BinaryExpression","left":{"type":"Identifier","identifier":"remaining"},"right":{"type":"NumericLiteral","value":1},"operator":"-"},"alternate":{"type":"Identifier","identifier":"timespan"}},"default":{"type":"Identifier","identifier":"timespan"}},{"type":"VariableDeclaration","variableType":"Property","identifier":"shouldInfect","value":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"prob"},"args":[{"type":"NumericLiteral","value":0.4}]}},{"type":"VariableDeclaration","variableType":"Property","identifier":"infected","value":{"type":"LogicalExpression","left":{"type":"LogicalExpression","left":{"type":"Identifier","identifier":"infected"},"right":{"type":"BinaryExpression","left":{"type":"Identifier","identifier":"remaining"},"right":{"type":"NumericLiteral","value":0},"operator":">"},"operator":"and"},"right":{"type":"LogicalExpression","left":{"type":"BinaryExpression","left":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"count"},"args":[{"type":"Identifier","identifier":"closeInfected"}]},"right":{"type":"NumericLiteral","value":0},"operator":">"},"right":{"type":"Identifier","identifier":"shouldInfect"},"operator":"and"},"operator":"or"},"default":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"prob"},"args":[{"type":"NumericLiteral","value":0.5}]}},{"type":"VariableDeclaration","variableType":"Property","identifier":"coloured","value":{"type":"Identifier","identifier":"infected"},"default":{"type":"BooleanLiteral","value":false}}]}]}
+{"type":"Program","body":[{"type":"ObjectDeclaration","identifier":"person","count":10,"body":[{"type":"VariableDeclaration","variableType":"Const","identifier":"x","value":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"random"},"args":[{"type":"NumericLiteral","value":0},{"type":"CallExpression","caller":{"type":"Identifier","identifier":"width"},"args":[]}]}},{"type":"VariableDeclaration","variableType":"Const","identifier":"y","value":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"random"},"args":[{"type":"NumericLiteral","value":0},{"type":"CallExpression","caller":{"type":"Identifier","identifier":"height"},"args":[]}]}},{"type":"VariableDeclaration","variableType":"Property","identifier":"close","value":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"filter"},"args":[{"type":"LambdaExpression","base":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"agents"},"args":[{"type":"Identifier","identifier":"person"}]},"param":"p","value":{"type":"LogicalExpression","left":{"type":"BinaryExpression","left":{"type":"MemberExpression","caller":{"type":"Identifier","identifier":"p"},"value":{"type":"Identifier","identifier":"x"}},"right":{"type":"NumericLiteral","value":0},"operator":">="},"right":{"type":"BinaryExpression","left":{"type":"MemberExpression","caller":{"type":"Identifier","identifier":"p"},"value":{"type":"Identifier","identifier":"x"}},"right":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"width"},"args":[]},"operator":"<="},"operator":"and"}}]}},{"type":"VariableDeclaration","variableType":"Property","identifier":"closest","value":{"type":"CallExpression","caller":{"type":"Identifier","identifier":"min"},"args":[{"type":"LambdaExpression","base":{"type":"Identifier","identifier":"close"},"param":"c","value":{"type":"MemberExpression","caller":{"type":"Identifier","identifier":"c"},"value":{"type":"Identifier","identifier":"x"}}}]}},{"type":"VariableDeclaration","variableType":"Property","identifier":"color","value":{"type":"BooleanLiteral","value":true}},{"type":"VariableDeclaration","variableType":"Property","identifier":"coloured","value":{"type":"OtherwiseExpression","left":{"type":"MemberExpression","caller":{"type":"Identifier","identifier":"closest"},"value":{"type":"Identifier","identifier":"color"}},"right":{"type":"BooleanLiteral","value":false}}}]}]}

code.txt

@@ -1,26 +1,12 @@
-agent person 30 {
-    const speed = 4;
-    property angle: random(0, 2 * pi()) = angle + choice(-0.1, 0.1);
-
-    property shouldStay = prob(0.5);
-
-    property xNew: 0 = (x + speed * cos(angle)) % width();
-    property yNew: 0 = (y + speed * sin(angle)) % height();
-
-    property x: random(50, width() - 50) = if shouldStay then x else xNew;
-    property y: random(50, height() - 50) = if shouldStay then y else yNew;
-
-    const distance = 20;
-
-    property people = agents(person);
-    property closePeople = filter(people => p => sqrt((p.x - x) * (p.x - x) + (p.y - y) * (p.y - y)) <= distance);
-    property closeInfected = filter(closePeople => c => c.infected == true);
-
-    const timespan = 200;
-    property remaining: timespan = if infected then remaining - 1 else timespan;
-
-    property shouldInfect = prob(0.4);
-    property infected: prob(0.5) = (infected and remaining > 0) or (count(closeInfected) > 0 and shouldInfect);
-
-    property coloured: false = infected;
+
+agent person 10 {
+    const x = random(0, width());
+    const y = random(0, height());
+
+    property close = filter(agents(person) => p => p.x >= 0 and p.x <= width());
+    property closest = min(close => c => c.x);
+
+    property color = true;
+
+    property coloured = closest.color otherwise false;
 }

src/parser/parser.ts

@@ -1,8 +1,8 @@
 import { exit } from "process";
 import { Token, TokenType } from "../lexer/lexer.types";
-import { BinaryExpression, BooleanLiteral, CallExpression, ConditionalExpression, Expression, Identifier, LambdaExpression, LogicalExpression, MemberExpression, NodeType, NumericLiteral, ObjectDeclaration, ParserValue, Program, Statement, UnaryExpression, VariableDeclaration, VariableType } from "./parser.types";
+import { BinaryExpression, BooleanLiteral, CallExpression, ConditionalExpression, Expression, Identifier, LambdaExpression, LogicalExpression, MemberExpression, NodeType, NumericLiteral, ObjectDeclaration, OtherwiseExpression, ParserValue, Program, Statement, UnaryExpression, VariableDeclaration, VariableType } from "./parser.types";
 import { Position } from "../symbolizer/symbolizer.types";
-import { getProgram } from "./optimizer";
+import { getProgram } from "./topology/optimizer";
 import { ErrorParser } from "../utils/errors";
 
 export class Parser {
@@ -141,7 +141,25 @@ export class Parser {
     }
 
     private parseExpression(): ParserValue {
-        return this.parseLambdaExpression();
+        return this.parseOtherwiseExpression();
+    }
+
+    private parseOtherwiseExpression(): ParserValue {
+        const left = this.parseLambdaExpression();
+
+        if (this.at().type === TokenType.Otherwise) {
+            this.next();
+
+            const right = this.parseLambdaExpression();
+
+            return {
+                type: NodeType.OtherwiseExpression,
+                left,
+                right
+            } as OtherwiseExpression;
+        }
+
+        return left;
     }
 
     private parseLambdaExpression(): ParserValue {

src/parser/parser.types.ts

@@ -20,6 +20,7 @@ export enum NodeType {
     CallExpression = "CallExpression",
     LambdaExpression = "LambdaExpression",
     MemberExpression = "MemberExpression",
+    OtherwiseExpression = "OtherwiseExpression",
 }
 
 export interface ParserValue {
@@ -96,6 +97,12 @@ export interface MemberExpression extends Expression {
     value: Expression;
 }
 
+export interface OtherwiseExpression extends Expression {
+    type: NodeType.OtherwiseExpression;
+    left: Expression;
+    right: Expression;
+}
+
 export interface Identifier extends Expression {
     type: NodeType.Identifier;
     identifier: string;

src/parser/optimizer.ts → src/parser/topology/optimizer.ts

@@ -1,6 +1,6 @@
-import { BinaryExpression, CallExpression, ConditionalExpression, Expression, Identifier, LambdaExpression, LogicalExpression, MemberExpression, NodeType, ObjectDeclaration, ParserValue, Program, UnaryExpression, VariableDeclaration } from "./parser.types";
+import { BinaryExpression, CallExpression, ConditionalExpression, Expression, Identifier, LambdaExpression, LogicalExpression, MemberExpression, NodeType, ObjectDeclaration, ParserValue, Program, UnaryExpression, VariableDeclaration } from "../parser.types";
 import { DependencyGraph, Node, topologicalSort } from "./topology";
-import { ErrorParser } from "../utils/errors";
+import { ErrorParser } from "../../utils/errors";
 
 const agentIdentifiers: string[] = [];
 

src/parser/topology.ts → src/parser/topology/topology.ts

@@ -1,4 +1,4 @@
-import { ErrorParser } from "../utils/errors";
+import { ErrorParser } from "../../utils/errors";
 
 export type DependencyGraph = { [key: string]: Node };
 

src/runtime/runtime.ts

@@ -10,6 +10,7 @@ import {
     NodeType,
     NumericLiteral,
     ObjectDeclaration,
+    OtherwiseExpression,
     ParserValue,
     Program,
     UnaryExpression,
@@ -43,6 +44,8 @@ export class Runtime {
 
     private output: RuntimeOutput = { type: ValueType.Output, step: 0, agents: [] };
 
+    private inOtherwiseExpression = false;
+
     constructor(program: Program, environment: Environment) {
         this.program = program;
 
@@ -167,6 +170,8 @@ export class Runtime {
                 return this.evaluateLambdaExpression(node as LambdaExpression, id);
             case NodeType.MemberExpression:
                 return this.evaluateMemberExpression(node as MemberExpression, id);
+            case NodeType.OtherwiseExpression:
+                return this.evaluateOtherwiseExpression(node as OtherwiseExpression, id);
             default:
                 throw new ErrorRuntime(`Unknown runtime node '${node.type}'`);
         }
@@ -213,6 +218,16 @@ export class Runtime {
         const leftHandSide = this.evaluateRuntimeValue(expression.left, id);
         const rightHandSide = this.evaluateRuntimeValue(expression.right, id);
 
+        // handle otherwise expression
+        if (this.inOtherwiseExpression && leftHandSide.type === ValueType.Null) {
+            return leftHandSide;
+        }
+
+        // handle otherwise expression
+        if (this.inOtherwiseExpression && rightHandSide.type === ValueType.Null) {
+            return rightHandSide;
+        }
+
         const isValid = (
             (expression.operator === "==" || expression.operator === "!=") &&
             (
@@ -239,6 +254,11 @@ export class Runtime {
         const operator = expression.operator;
         const value = this.evaluateRuntimeValue(expression.value, id);
 
+        // handle otherwise expression
+        if (this.inOtherwiseExpression && value.type === ValueType.Null) {
+            return value;
+        }
+
         if (operator === "-") {
             if (value.type !== ValueType.Number) {
                 throw new ErrorRuntime("Unary expression with '-' operator requires numeric value as operand");
@@ -308,6 +328,16 @@ export class Runtime {
         const leftHandSide = this.evaluateRuntimeValue(expression.left, id);
         const rightHandSide = this.evaluateRuntimeValue(expression.right, id);
 
+        // handle otherwise expression
+        if (this.inOtherwiseExpression && leftHandSide.type === ValueType.Null) {
+            return leftHandSide;
+        }
+
+        // handle otherwise expression
+        if (this.inOtherwiseExpression && rightHandSide.type === ValueType.Null) {
+            return rightHandSide;
+        }
+
         if (leftHandSide.type === ValueType.Boolean && rightHandSide.type === ValueType.Boolean) {
             let result;
 
@@ -330,6 +360,11 @@ export class Runtime {
     private evaluateConditionalExpression(expression: ConditionalExpression, id: string): RuntimeValue {
         const condition = this.evaluateRuntimeValue(expression.condition, id);
 
+        // handle otherwise expression
+        if (this.inOtherwiseExpression && condition.type === ValueType.Null) {
+            return condition;
+        }
+
         if (condition.type !== ValueType.Boolean) {
             throw new ErrorRuntime("Conditional expression requires a boolean expression as its condition");
         }
@@ -385,6 +420,11 @@ export class Runtime {
     private evaluateMemberExpression(expression: MemberExpression, id: string): RuntimeValue {
         const caller = this.evaluateRuntimeValue(expression.caller, id);
 
+        // handle otherwise expression
+        if (this.inOtherwiseExpression && caller.type === ValueType.Null) {
+            return caller;
+        }
+
         if (caller.type !== ValueType.Agent) {
             throw new ErrorRuntime("The caller of member expression must be of type 'agent'");
         }
@@ -405,6 +445,18 @@ export class Runtime {
         return value;
     }
 
+    private evaluateOtherwiseExpression(expression: OtherwiseExpression, id: string): RuntimeValue {
+        this.inOtherwiseExpression = true;
+        const left = this.evaluateRuntimeValue(expression.left, id);
+        this.inOtherwiseExpression = false;
+
+        if (left.type === ValueType.Null) {
+            return this.evaluateRuntimeValue(expression.right, id);
+        }
+
+        return left;
+    }
+
     private customModulo(a: number, b: number): number {
         return ((a % b) + b) % b;
     }

src/runtime/runtime.types.ts

@@ -3,7 +3,7 @@ export enum ValueType {
     Number = "Number",
     Boolean = "Boolean",
     Function = "Function",
-    Void = "Void",
+    Null = "Null",
     Agent = "Agent",
     Agents = "Agents",
     Lambda = "Lambda",
@@ -43,6 +43,10 @@ export interface RuntimeAgent {
     variables: Map<string, RuntimeValue>;
 }
 
+export interface NullValue extends RuntimeValue {
+    type: ValueType.Null;
+}
+
 export interface AgentValue extends RuntimeValue {
     type: ValueType.Agent;
     value: RuntimeAgent;