JavaScript generator for nub.

generated.js

// Input:
//     def printRange(from, to) { let i = from; while(i < to) { println(i); i = i + 1; } } printRange(1, 10); // Loop
// Raw output:
//     (function(){ let __last__ = 0;let printRange = function(from,to){ let __last__ = 0;let i = from;__last__ = i;__last__ = (function(){ let __last__ = 0;while( (i<to) ){__last__ = console.log(i);;__last__ = (i = (i+1));}return __last__;})();;return __last__;};__last__ = printRange;__last__ = (printRange)(1,10);return __last__;})();

(function() {
    let __last__ = 0;
    let printRange = function(from, to) {
        let __last__ = 0;
        let i = from;
        __last__ = i;
        __last__ = (function() {
            let __last__ = 0;
            while ((i < to)) {
                __last__ = console.log(i);;
                __last__ = (i = (i + 1));
            }
            return __last__;
        })();;
        return __last__;
    };
    __last__ = printRange;
    __last__ = (printRange)(1, 10);
    return __last__;
})();

JavaScriptGenerator.java

package com.github.kmizu.nub;

import java.util.*;

public class JavaScriptGenerator implements AstNode.ExpressionVisitor<Object> {

    private Set<String> functions = new HashSet<>();

    private StringBuilder stringBuilder = new StringBuilder();


    public Object visitBinaryOperation(AstNode.BinaryOperation node) {
        switch (node.operator()) {
            case "+":
            case "-":
            case "*":
            case "<=":
            case ">=":
            case "<":
            case ">":
            case "&&":
            case "||":
                stringBuilder.append('(');
                node.lhs().accept(this);
                stringBuilder.append(node.operator());
                node.rhs().accept(this);
                stringBuilder.append(')');
                return null;
            case "/":
                stringBuilder.append("((");
                node.lhs().accept(this);
                stringBuilder.append(node.operator());
                node.rhs().accept(this);
                stringBuilder.append("|0)");
                return null;
            case "==":
                stringBuilder.append('(');
                node.lhs().accept(this);
                stringBuilder.append("===");
                node.rhs().accept(this);
                stringBuilder.append(')');
                return null;
            case "!=":
                stringBuilder.append('(');
                node.lhs().accept(this);
                stringBuilder.append("!==");
                node.rhs().accept(this);
                stringBuilder.append(')');
                return null;
            default:
                throw new RuntimeException("cannot reach here");
        }
    }

    @Override
    public Object visitNumber(AstNode.Number node) {
        stringBuilder.append(node.value());
        return null;
    }

    @Override
    public Object visitLetExpression(AstNode.LetExpression node) {
        stringBuilder.append("let ");
        stringBuilder.append(node.variableName());
        stringBuilder.append(" = ");
        Object value = node.expression().accept(this);
        return null;
    }

    @Override
    public Object visitAssignmentOperation(AstNode.AssignmentOperation node) {
        stringBuilder.append("(");
        stringBuilder.append(node.variableName());
        stringBuilder.append(" = ");
        Object value = node.expression().accept(this);
        stringBuilder.append(")");
        return null;
    }

    @Override
    public Object visitPrintExpression(AstNode.PrintExpression node) {
        stringBuilder.append("console.log(");
        node.target().accept(this);
        stringBuilder.append(");");
        return null;
    }

    @Override
    public Object visitPrintlnExpression(AstNode.PrintlnExpression node) {
        stringBuilder.append("console.log(");
        node.target().accept(this);
        stringBuilder.append(");");
        return null;
    }

    private void visitExpressions(List<AstNode.Expression> nodes)
    {
        for (AstNode.Expression e : nodes) {
            if(e instanceof AstNode.DefFunction) {
                e.accept(this);
                stringBuilder.append(";");
                stringBuilder.append("__last__ = ");
                stringBuilder.append(((AstNode.DefFunction)e).name());
            } else if(e instanceof AstNode.LetExpression) {
                e.accept(this);
                stringBuilder.append(";");
                stringBuilder.append("__last__ = ");
                stringBuilder.append(((AstNode.LetExpression)e).variableName());
            } else {
                stringBuilder.append("__last__ = ");
                e.accept(this);
            }
            stringBuilder.append(";");
        }
    }

    @Override
    public Object visitExpressionList(AstNode.ExpressionList node) {
        stringBuilder.append("(function(){ let __last__ = 0;"); {
            visitExpressions(node.expressions());
            stringBuilder.append("return __last__;})();");
        }
        return null;
    }

    @Override
    public Object visitWhileExpression(AstNode.WhileExpression node) {
        stringBuilder.append("(function(){ let __last__ = 0;");
        {
            stringBuilder.append("while( ");
            node.condition().accept(this);
            stringBuilder.append(" ){");
            {
                visitExpressions(node.body());
                stringBuilder.append("}");
            }
            stringBuilder.append("return __last__;})();");
        }
        return null;
    }

    @Override
    public Object visitIfExpression(AstNode.IfExpression node) {
        stringBuilder.append("(function(){ let __last__ = 0;"); {
            stringBuilder.append("if( ");
            node.condition().accept(this);
            stringBuilder.append(" ){");
            {
                visitExpressions(node.thenClause());
                stringBuilder.append("}");
            }
            if(node.elseClause().size() > 0) {
                stringBuilder.append("else{"); {
                    visitExpressions(node.elseClause());
                    stringBuilder.append("}");
                }
            }
            stringBuilder.append("return __last__;})();");
        }
        return null;
    }

    @Override
    public Object visitDefFunction(AstNode.DefFunction node) {
        stringBuilder.append("let ");
        stringBuilder.append(node.name());
        stringBuilder.append(" = function(");
        boolean isFirst = true;
        for(String e:node.args()) {
            stringBuilder.append(e);
            if(isFirst){
                isFirst = false;
                stringBuilder.append(",");
            }
        }
        stringBuilder.append("){ let __last__ = 0;"); {
            visitExpressions(node.body());
            stringBuilder.append("return __last__;}");
        }
        return null;
    }

    @Override
    public Object visitIdentifier(AstNode.Identifier node) {
        stringBuilder.append(node.name());
        return null;
    }

    public Object evaluate(AstNode.ExpressionList program) {
        stringBuilder = new StringBuilder();
        program.accept(this);
        return stringBuilder.toString();
    }

    @Override
    public Object visitFunctionCall(AstNode.FunctionCall node) {
        //if(!functions.contains(node.name())) {
        //    throw new NubRuntimeException("function " + node.name().name() + " is not defined");
        //}
        {
            stringBuilder.append("(");
            node.name().accept(this);
            stringBuilder.append(")(");
            boolean isFirst = true;
            for(AstNode.Expression e:node.params()) {
                e.accept(this);
                if(isFirst){
                    isFirst = false;
                    stringBuilder.append(",");
                }
            }
            stringBuilder.append(")");
            return null;
        }
    }

    @Override
    public Object visitReturn(AstNode.Return node) {
        stringBuilder.append("return ");
        node.expression().accept(this);
        stringBuilder.append(";");
        return null;
    }
}