function(expr, context) {
      if(context.isConstant(expr)) {
        return new OperatorNode('*', 'multiply', [
          expr.clone(),
          context.variable.clone()
        ]);
      }
    }
function(expr, context) {
      if(context.isConstant(expr)) {
        return new OperatorNode('*', 'multiply', [
          expr.clone(),
          context.variable.clone()
        ]);
      }
    }
function ( expr , context ) { if ( context . isConstant ( expr ) ) { return new OperatorNode ( '*' , 'multiply' , [ expr . clone ( ) , context . variable . clone ( ) ] ) ; } }
integral(c, x) = c * x
integral ( c x ) = c * x