Java Expression Evaluator

Last updated: Fri Oct 20 12:50:46 EDT 2017. The expression nonterminal allows us to pick any kind of expression as an operand, regardless of the operator we picked. The & operator always evaluates both expressions. An instance of the ExpressionEvaluator can be obtained via the JspContext / PageContext. Here you can learn C, C++, Java, Python, Android Development, PHP, SQL, JavaScript,. Interested candidates should possess relevant qualifications with at least 10 years work experience. I am NOT asking how to write a ternary expression. An easy to use editor for crontab schedules. /* class Expression Carol Wolf Fall 2001 The following is a Java application that uses recursive descent to evaluate an infix expression. A regular expression is a “prefix expression” if it starts with a caret (^) or a left anchor (\A), followed by a string of simple symbols. An operator is a symbol (or sometimes word) used to manipulate expressions. Many functions and operations returns boolean objects. It started out as a calculator component for TradeTrax , but quickly matured into a standalone project. Java applications process data by evaluating expressions, which are combinations of literals, method calls, variable names, and operators. To make best use of computer resources FlexiHub is a must have software for mid to large scale. Subexpressions can be parsed in the same way as the whole expression (you again found the summands inside the brackets, then factors, and then atoms). We can run Groovy code from Java code in several ways. ; The AST must be used in evaluation, also, so the input may not be directly evaluated (e. Only then, the test expression is checked. Create a stack-based evaluator for an expression in reverse Polish notation (RPN) that also shows the changes in the stack as each individual token is processed as a table. Java Conditional or Relational Operators: The relational operators determine the relationship that one operand has to the other. Java Program to Evaluate PostFix Expressions. //***** import jss2. A function that doesn't have a name and doesn't belong to any class. Following is the example that shows evaluation of the Postfix expression using stack as data structure. Both symbolical and numerical computations are supported. after(ExpressionBasedPostInvocationAdvice. With our new 0. JSONPath Syntax Example '$. Tal Weiss has written a good blog on how Java compiles the lambda expressions into bytecode. The class com. There are times when you need to evaluate some expression in your program. You can evaluate MATLAB ® statements from Java ® using the MatlabEngine eval and evalAsync methods. If you run the benchmark for yourself, you might find a couple of interesting things: the “Janino” test continuously warns about recompilation. Java: Select if you want to debug only code written in Java or Kotlin—the Java debugger ignores any breakpoints or watches you set in your native code. Freeware Secure Remote Ping downloads. A CRON expression is a string of 6 or 7 fields, separated by a white space, that represents a schedule. Example Code, OpenSource, Tips. Abu Naser Abstract: This study presents an Intelligent Tutoring System called JEE-Tutor for teaching Java operator precedence, associativity and expressions evaluation to freshman students in the Faculty of Engineering and Information Technology in Al-Azhar University. Any comments are appreciated. For example, return user. The above code computes the value of a mathematical expression supplied at command line by using the concept of converting infix to postfix,then evaluating the postfix expression. NET Regex class library directly. I've been reading the C++ for dummies book and I'm loving it! I'm on the section where he is talking about short circuit evaluation. Matching values Normalized path expressions Jayway options. You can use the following algorithm to evaluate postfix expressions: Initialize an empty stack. This is also not available without starting the app, whereas e. Table of Contents1 Expression Evaluation2 Assignment Operator Augmentation3 Increment & Decrement Operators3. Check out t. Evaluating Expressions. It is the positioning of the exponent, the 3 in this example, to the right and up from the base, the 2 in this example,. The rules of precedence limit that. This is first part of a series about writing expression evaluator in C#. 4, from Java(TM) SE Runtime Environment (build 1. 9/22/2008 A + A-Email Print. All the normal rules for evaluating expressions, including variable substitution, are performed by the eval function. Sometimes you can create something that is not text/string based, that is you construct the expression in a different way - typically so it is easier to validate, evaluate, etc. From splitting a bill at a restaurant to shopping for a DIY project, most of our activities that involve numbers require us to form math expressions. Create a new Visual C# Console Application in Visual Studio. Expression definition, the act of expressing or setting forth in words: the free expression of political opinions. To evaluate internet sources: The internet is a great place to find both scholarly and popular sources, but it's especially important to ask questions about authorship and publication when you're evaluating online resources. NET Regex Tester. The placeholder expressions are surrounded by ${}. The Token class is used to store the name and value of each operator and operand in the expression. You first create a Pattern object which defines the regular expression. It can handle normal arithmetics (includings powers wit ^ or ** ), builtin functions like sin() and variables. If an operand is * encountered, it is pushed onto the stack. When you supply values for interpolations or directive parameters you can use variables or more complex expressions. The Evaluate method takes an XPath expression, evaluates it and returns a W3C XPath type of Boolean, Number, String, or Node Set based on the result of the. execute the script. Examples: • 2 + 3 is an expression • 3 − x/2 is also an expression. As Postfix expression is without parenthesis and can be evaluated as two operands and an operator at a time, this becomes easier for the compiler and the computer to handle. See source code here:. We have seen How to select XML elements value as text using text() function and counted matching elements using count() function. NameValuePair;. Expression Evaluation. For example, the regex /^abc. Here b is false, so b && c must be false regardless of whether c is or is not true, so Java doesn't bother checking the value of c. java in the previous article to run this demo. Description: Assignments in Boolean conditions can be confused with equality tests and make the condition more difficult to understand. PostFix expression evaluator - Java This program evaluates postfix expressions entered by the user. There are a number of good articles in CodeProject on this subject. Many functions and operations returns boolean objects. com> To: robots Subject: The robots mailing list at WebCrawler From: Martijn Koster Date: Thu, 12 Oct 1995 14:39:19 -0700 Sender: owner-robots Precedence: bulk Reply-To: [email protected] String and in the “new I/O” package). In Java SE 7, a single method interface can be implemented with one of the following options. 0 2018-07-21 17:38 Regina Obe * [r16656] Update templates 2018-07-21 16:35. The class com. 7801 to display as $12. see-programming is a popular blog that provides information on C programming basics, data structure, advanced unix programming, network programming, basic linux commands, interview question for freshers, video tutorials and essential softwares for students. Evaluating an expression typically produces a new value, which can be stored in a variable, used to make a decision, and so on. Any Groovy expression can be interpolated in all string literals, apart from single and triple-single-quoted strings. type' See also JSONPath expressions. Model import oracle. The following program will convert a infix expression into a postfix expression, then evaluate the value using the Evaluator in the previous article. In this part of the Java tutorial, we will talk about expressions. In this paper it is presented a solution that combines both options: the problem can be expressed at run-time as a string of chars that are converted to Java code, compiled and loaded dynamically. For example, an operand of a * expression cannot be a + expression , since the latter has lower precedence. Last updated: Fri Oct 20 12:50:46 EDT 2017. java The prefix calculator that exercises an ExpressionTree object (link to the same as a text file) — 44 lines. The operators + and - work as unary operators as well. First go to the Algebra Calculator main page. 0M) id AA20349; Thu, 12 Oct 95 14:39:19 -0700 Message-Id: 9510122139. I've assumed you know at least a little bit about context-free grammars and parsing. JavaScript XPath Implementation. Infix Expressions are harder for Computers to evaluate because of the addional work needed to decide precedence. a) If the element is a number, push it into the stack. When an expression is said to have evaluated to a value, the process has been completed. regex package. JSONPath Syntax Example '$. I was using various ad-hoc techniques and free libraries for this. //***** // PostfixEvaluator. Example Code, OpenSource, Tips. You can use the following algorithm to evaluate postfix expressions: Initialize an empty stack. much faster than you can find the parentheses for the first expression. An instance of the ExpressionEvaluator can be obtained via the JspContext / PageContext. When there are multiple instances of the same precedence, Java reads from left to right. The Prefix notation is also known as Polish Notation. Parsing Expressions by Recursive Descent. As you can see execution of simple bits of code is pretty straight forward. me(' 2 * 4 + 2') == 10 assert Eval. Read and write an algebraic expression containing a variable From. This process goes on until the test expression is evaluated to false. It enables users to schedule tasks to run periodically at a specified date/time. Infix Expression : Any expression in the standard form like "2*3-4/5" is an Infix(Inorder) expression. Type the following: First type the expression 2x. Below is the syntax javac Evaluate. The result of the CASE expression is the evaluation of the THEN expression that corresponds to the first WHEN expression for which the comparison is true. Software delivers easy to use API for JAVA, Android and C#. Here is a simple example that demonstrates how you can use Java regular expression to find a string or a phrase in a text file. Evaluation of an infix expression that is fully parenthesized using stack in java. Download Java Expression Evaluator for free. Can avoid this by checking for null in your expression. For example, if you want to solve the following Kepler's equation;. The only difference is the format. You will need PostfixEvaluator. Expression Evaluation The debugger now enables you to evaluate expressions in variable watch window as well as debug console at runtime. 0 2018-07-21 17:53 Regina Obe * [r16657] Add license info to tiger_geocoder code Closes #3287 for PostGIS 2. The syntax consists of a pair of parentheses. 4, from Java(TM) SE Runtime Environment (build 1. In this section we'll discuss methods that are related to regular expressions. An extensible general purpose expression evaluator in Java. Terms and names e= xplained. This means that expressions will only be evaluated as far as necessary. Create a dictionary. Standard boolean and mathematical operators. Jep is a Java library for parsing and evaluating mathematical expressions. ‘push’ operation is used to add an element to stack and ‘pop’ operation is used to remove an element from stack. Infix expression is the most commonly used expression and we are all familiar with this. The simplest arithmetic expressions in Java are made up of two operands and one operator. Parsing Expressions by Recursive Descent. It needs no external library in order to run. The position is located in Abuja. Evaluating an expression typically produces a new value, which can be stored in a variable, used to make a decision, and so on. In postfix notation, the need for parentheses is eliminated and the priority of the operators is no longer relevant. Java: Select if you want to debug only code written in Java or Kotlin—the Java debugger ignores any breakpoints or watches you set in your native code. You can also add add as many strings as possible by including the + operator between them. Java Expression Language (JEXL) JEXL is a library intended to facilitate the implementation of dynamic and scripting features in applications and frameworks written in Java. Chapter 7 Expressions and Assignment Statements Introduction Expressions are the fundamental means of specifying computations in a programming language. The XPathNavigator class provides the Evaluate method to evaluate an XPath expression. The library used in this page is jaxp, Java API for XML Processing, version 1. java /** * Expression Tree of TreeNode objects, built from a prefix expression. Jasmine parses the expression and then uses the excellent ASM byte code manipulation library to convert it to Java byte code. It enables users to schedule tasks to run periodically at a specified date/time. Operand Evaluation Order 1. //***** import jss2. exp4j is capable of evaluating expressions and functions in the real domain. C Program to Evaluate POSTFIX Expression Using Stack, the program implemented with push and pop operations. The "convert" process working fine - it outputs the postfix value like it should. Consider a situation, Employee object contains many informations such as id, name, emailId etc. The first is a. Software delivers easy to use API for JAVA, Android and C#. To start, enter a regular expression and a test string. Evaluation of infix expressions. JSONPath Online Evaluator - jsonpath. Only then, the test expression is checked. Evaluating Expressions. Here is an example that shows that the second expression is not automatically. ‘peek’ operation. It's a handy way to test regular expressions as you write them. Evaluating an infix-notation expression (that's when the operators appear between the operands, as in A + B) is a classic computer science problem, and most computer science majors probably had to do it in their "Compilers and Interpreters" class. java * Execution: java Evaluate * Removing them yields an expression known as a postfix expression. For example, if x is the number 8 and y is 5, the value of (x + y)/2 resolves to the numerical value 6. Expressions are constructed from operands and operators. Precision: low. Evaluate a string expression java-forums. Generally postfix expressions are free from Operator Precedence thats why they are preferred in Computer system. Left-associativity (left-to-right) means that it is processed as (a * b) * c, while right-associativity (right-to-left) means it is interpreted as a * (b * c). A very simple and easy way is to use the Eval class. The rules of precedence limit that. Postfix Expression Evaluation using Stack Data Structure. Can we keep track of the expression's value as well so as to avoid the evaluation at the very end of recursion?. Jayway JsonPath Evaluator - Go! JSONPath options. You can evaluate MATLAB ® statements from Java ® using the MatlabEngine eval and evalAsync methods. Learn more. JSONPath expressions always refer to a JSON structure in the same way as XPath expression are used in combination with an XML document. 11/04/2016; 2 minutes to read +3; In this article. Evaluation of postfix expression ; Algorithm for Evaluation of Postfix Expression; Infix to Postfix Expression Conversion ; Algorithm for Infix to Postfix Conversion ; Stack Data Structure Using C Programming ; Infix to Postfix Conversion Example (Using Stack) C Program to Convert Infix Expression to Postfix Using Stack; Video 1 ; Video 3. org Hi all, I have like crazy 20 variables and any five of them will decide how the user want the output. Pattern javadoc) Wikipedia on regular expressions; A regular expressions tutorial; External sample parsing Tomcat. The order of evaluation of operators in an expression is determine. type' See also JSONPath expressions. 1) Create a stack to store operands (or values). regex package. If you need more examples or solutions, please contact me. The basic syntax is very similar to the new JAVA Expression Language, introduced with the JSP 2. An expression needs to be parsed and compiled only once, after which the expression can be evaluated repeatedly. An easy to use editor for crontab schedules. Or give this example a try. Integer Division. Using XPath Expressions, we can find nodes in any xml document satisfying the query string. There are no precedence rules to learn, and parentheses are never needed. At the same time it generates the corresponding postfix expression. This is due on the 23rd. Java Programming - How do I evaluate a string of arithmetic expression? For example, I have: string x = "1+2+3". The expression is evaluated but is not loaded in place of the current document. Classes that implement an expression language expose their functionality via this abstract class. A special construct (?ifthen|else) allows you to create conditional regular expressions. Java 4 and later include an excellent regular expression library in the form of the java. Next, we need blobs of code to implement the evaluation logic for each kind of expression we can parse. The rules of precedence limit that. An expression can be thought of as a formula that is made up of multiple pieces. Matching values Normalized path expressions Jayway options. The canonical reference for building a production grade API with Spring. Thus precedence of operators and availability of brackets must be kept in mind for evaluating a given prefix string to result in a correct output. A multi-faceted language for the Java platform. The XPathNavigator class provides the Evaluate method to evaluate an XPath expression. You can use the void operator to specify an expression as a hypertext link. RegexSearch is a Java application that searches multiple files for specified text or a regular expression. You can repeat Step 2 many times by entering different XPath expressions of your XML document. The code is mostly from the Aray v7. The rules of precedence limit that. There are a number of good articles in CodeProject on this subject. For example, an operand of a * expression cannot be a + expression , since the latter has lower precedence. Java expressions. cwd - The working directory of the program. ; The AST must be used in evaluation, also, so the input may not be directly evaluated (e. See source code here:. HackerRank for Work is the leading end-to-end technical recruiting platform for hiring developers. I needed something which would do basic math with variables, expressions like: "Top+2", "Bottom-2" and "(Right+1-Left)/2". That is, your class will contain a private Java Stack object, and it will use Java's provided methods for operations on the class. The Stack you will use is from the Java API: java. HOME C C++ DS Java AWT Collection Jdbc JSP Servlet SQL PL/SQL C-Code C++-Code Java-Code Project Word Excel. You can easily use the ExpressionInterpreter from your own code. May 5, 2015 Ankur Leave a comment. NET regex reference. There could be duplicated class names in different projects. If the current character of the expression is an operand, we push it to the stack else if current character is a operator we pop top two elements from the stack, evaluate them using the current operator and push the result back to the stack. In this page you can check a XPath expression against your XML. Question: Java (Evaluate expression) Modify. Parsing expressions by recursive descent poses two classic. com offers free software downloads for Windows, Mac, iOS and Android computers and mobile devices. Single Mode Arithmetic Expressions An arithmetic expression is an expression using additions +, subtractions -, multiplications *, divisions /, and exponentials **. 1 Example 13. In Infix expression, the operator is between two operands, as in 1 + 2, or “5 + ((2 + 6) × 9) − 8”. java to add operators ^ for exponent and % for modulus. Conceptually, there are two types of expressions: those that assign a value to a variable, and those that simply have a value. NameValuePair;. Files are shown in a scrollable window with the matched text highlighted. Following is the example that shows evaluation of the Postfix expression using stack as data structure. In postfix notation, the need for parentheses is eliminated and the priority of the operators is no longer relevant. User can evaluate instantly a string setting variables, adding its own functions or operators. The LINQ support classes include the class Expression, you can build these yourself at runtime by adding/removing/inserting nodes, so for any input expression (text) there is an equivalent expression tree. I was using various ad-hoc techniques and free libraries for this. For advanced regular expressions the java. An extensible general purpose expression evaluator in Java. You can use it to evaluate small Groovy scripts that don't need large Binding objects. 1) Create a stack to store operands (or values). The leaves of a binary expression tree are operands, such as constants or variable names, and the other nodes contain operators. RegEx can be used to check if a string contains the specified search pattern. JBEE - Java Basic Expression Evaluator (library) JBEE is yet another parser and evaluator for arithmetic expressions. There are a few other regex packages for Java, and you may occasionally meet code using them, but pretty well all code from this century can be. Appendix A: Operator Precedence in Java. Alrighty, here goes. The most common Boolean expressions compare the value of a variable with the value of some other variable, a constant, or perhaps a simple arithmetic. Java Regular Expression Tester. I needed something which would do basic math with variables, expressions like: “Top+2”, “Bottom-2” and “(Right+1-Left)/2”. The "convert" process working fine - it outputs the postfix value like it should. a) If the element is a number, push it into the stack. Watch on YouTube You can also ‘watch’ this post on YouTube I have some code which fills a dynamic array with “*” to simulate a set of ‘pixels’ - whatever. It supports some SQL predicase (is null, like, in, between) and almost all Oracle's and MaxDB's functions. In this case, the expression evaluator can take in a set of parameters and use them as additional input. The rules of precedence limit that. Some common situation includes on a program contest evaluation system, on a dynamic business logic control, on evaluation of dynamic math expression, or even on evaluation of test case. compile() is invoked as a method of a regular expression. exp4j comes with a standard set of built-in functions and operators. Inspired by Rubular it gives you a simple way to test javascript regular expressions as you write them. 2 For projects that support PackageReference , copy this XML node into the project file to reference the package. + 1 or more of previous expression. {"categories":[{"categoryid":387,"name":"app-accessibility","summary":"The app-accessibility category contains packages which help with accessibility (for example. JSONPath expressions always refer to a JSON structure in the same way as XPath expression are used in combination with an XML document. Note that while reversing the string you must interchange left and right parentheses. Arithmetic expressions evaluate to numeric values; a Boolean expression, sometimes called a predicate , evaluates to false or true. 7801 to display as $12. NET Regular Expression Tester and Reference. You can actually use this API in your Java code, not unlike how you might use other expression languages to evaluate strings for value. If a class have an entity reference, it is known as Aggregation. Software delivers easy to use API for JAVA, Android and C#. This function is extremely powerful simply because it evaluates any JavaScript (JScript) expression, no matter. The Token class is used to store the name and value of each operator and operand in the expression. Step 4: Repeatedly pop from the stack and add it to the postfix expression until the stack is empty ; Step 5: EXIT ; Prefix. In this lesson, we have described how we can evaluate Prefix and Postfix expressions efficiently using stack data structure. Y'all are misunderstanding - I want to dynamically evaluate ANY expression this is just the simplest example. regular expressions testing, online check, replacement, evaluation i. - ExpressionEvaluator. Last updated: Fri Oct 20 12:50:46 EDT 2017. After that I explain when JavaScript makes a variable false and finally how to see if an object exists. Although Postfix and Prefix notations have similar complexity, Postfix is slightly easier to evaluate in simple circumstances, such as in some calculators (e. If an XPath expression is only used once, you can use one of the four evaluate() methods in the XPath interface to evaluate the XPath expression without compiling it first. H4H Affiliate Program for osCommerce is a PHP based script designed to support and increase traffics of osCommerce. The not keyword can also be used to inverse a boolean type. The vector product and the scalar product are the two ways of multiplying vectors which see the most application in physics and astronomy. Need help? Post your question and get tips & solutions from a community of 435,961 IT Pros & Developers. Expressions are constructed from operands and operators. In the discussions below we consider all operators to be binary. An instance of the ExpressionEvaluator can be obtained via the JspContext / PageContext. When you supply values for interpolations or directive parameters you can use variables or more complex expressions. Create a stack-based evaluator for an expression in reverse Polish notation (RPN) that also shows the changes in the stack as each individual token is processed as a table. Name: Assignment in Boolean expression. java -cp janino. When writing your own calculator it is necessary to build a converter that can transform an input mathematical expression such as ( 1 + 8 ) – ( ( 3 * 4 ) / 2 ), into a format that is more suited for evaluation by computers. NET regular expression tester with real-time highlighting and detailed results output. You can repeat Step 2 many times by entering different XPath expressions of your XML document. java The prefix calculator that exercises an ExpressionTree object (link to the same as a text file) — 44 lines. This class is a simple helper on top of GroovyShell. The JSTL expression language is one of JSTL's most exciting features. The position is located in Abuja. Assumes the // operands are constants. Given that they are harder to evaluate, they are generally converted to one of the two remaining forms. Using PEMDAS to Evaluate Numerical Expressions. We have rules to indicate which operations take precedence over others, and we often use parentheses to override those rules. Try it now: 2x @ x=3 Clickable Demo Try entering 2x @ x=3 into the text box. Let's see a couple of examples to split a comma separated String in Java. These methods are similar to the MATLAB eval function. EDIT:What i’m actually looking for is something that would spit out an answer to this expression, maybe parse was a bad word. a) If the element is a number, push it into the stack. Example Problem Evaluate the expression 2x for x=3. The table in section Expressions, Statements, and Blocks shows the relative precedence assigned to the operators in the Java platform. mXparser is a super easy, rich, fast and highly flexible math expression parser library (parser and evaluator of mathematical expressions / formulas provided as plain text / string). Scanner; import java. Simply put, cron is a basic utility available on Unix-based systems. Expressions in JsonPath are basically code snippets that evaluate to the Boolean value. 0 release, we’re adding two new exciting features: Expression Evaluation and Support Step Filters. Lambda expressions simplify the use of interfaces that declare a single abstract method, which are also called functional interfaces. In this section we'll discuss methods that are related to regular expressions. HOME C C++ DS Java AWT Collection Jdbc JSP Servlet SQL PL/SQL C-Code C++-Code Java-Code Project Word Excel. Many functions and operations returns boolean objects. Please wait while Regex Hero loads. Using this little language, you specify the rules for the set of possible strings that you want to. On evaluation, an optional scope can be provided, which is used to resolve symbols and to write assigned variables or functions. To test JAVA regular expression you can use java-applet. The parentheses surrounding the expression are optional, but it is good style to use them. Variables: fetch the value from memory 2. Welcome to Java XPath Example Tutorial. 6 Testing Regular Expressions¶ Since JMeter 2. Java Forums on Bytes. It is the positioning of the exponent, the 3 in this example, to the right and up from the base, the 2 in this example,. A lambda expression is an anonymous function. Assumes the // operands are constants. The fact-checkers, whose work is more and more important for those who prefer facts over lies, police the line between fact and falsehood on a day-to-day basis, and do a great job. Today, my small contribution is to pass along a very good overview that reflects on one of Trump’s favorite overarching falsehoods. Namely: Trump describes an America in which everything was going down the tubes under  Obama, which is why we needed Trump to make America great again. And he claims that this project has come to fruition, with America setting records for prosperity under his leadership and guidance. “Obama bad; Trump good” is pretty much his analysis in all areas and measurement of U.S. activity, especially economically. Even if this were true, it would reflect poorly on Trump’s character, but it has the added problem of being false, a big lie made up of many small ones. Personally, I don’t assume that all economic measurements directly reflect the leadership of whoever occupies the Oval Office, nor am I smart enough to figure out what causes what in the economy. But the idea that presidents get the credit or the blame for the economy during their tenure is a political fact of life. Trump, in his adorable, immodest mendacity, not only claims credit for everything good that happens in the economy, but tells people, literally and specifically, that they have to vote for him even if they hate him, because without his guidance, their 401(k) accounts “will go down the tubes.” That would be offensive even if it were true, but it is utterly false. The stock market has been on a 10-year run of steady gains that began in 2009, the year Barack Obama was inaugurated. But why would anyone care about that? It’s only an unarguable, stubborn fact. Still, speaking of facts, there are so many measurements and indicators of how the economy is doing, that those not committed to an honest investigation can find evidence for whatever they want to believe. Trump and his most committed followers want to believe that everything was terrible under Barack Obama and great under Trump. That’s baloney. Anyone who believes that believes something false. And a series of charts and graphs published Monday in the Washington Post and explained by Economics Correspondent Heather Long provides the data that tells the tale. The details are complicated. Click through to the link above and you’ll learn much. But the overview is pretty simply this: The U.S. economy had a major meltdown in the last year of the George W. Bush presidency. Again, I’m not smart enough to know how much of this was Bush’s “fault.” But he had been in office for six years when the trouble started. So, if it’s ever reasonable to hold a president accountable for the performance of the economy, the timeline is bad for Bush. GDP growth went negative. Job growth fell sharply and then went negative. Median household income shrank. The Dow Jones Industrial Average dropped by more than 5,000 points! U.S. manufacturing output plunged, as did average home values, as did average hourly wages, as did measures of consumer confidence and most other indicators of economic health. (Backup for that is contained in the Post piece I linked to above.) Barack Obama inherited that mess of falling numbers, which continued during his first year in office, 2009, as he put in place policies designed to turn it around. By 2010, Obama’s second year, pretty much all of the negative numbers had turned positive. By the time Obama was up for reelection in 2012, all of them were headed in the right direction, which is certainly among the reasons voters gave him a second term by a solid (not landslide) margin. Basically, all of those good numbers continued throughout the second Obama term. The U.S. GDP, probably the single best measure of how the economy is doing, grew by 2.9 percent in 2015, which was Obama’s seventh year in office and was the best GDP growth number since before the crash of the late Bush years. GDP growth slowed to 1.6 percent in 2016, which may have been among the indicators that supported Trump’s campaign-year argument that everything was going to hell and only he could fix it. During the first year of Trump, GDP growth grew to 2.4 percent, which is decent but not great and anyway, a reasonable person would acknowledge that — to the degree that economic performance is to the credit or blame of the president — the performance in the first year of a new president is a mixture of the old and new policies. In Trump’s second year, 2018, the GDP grew 2.9 percent, equaling Obama’s best year, and so far in 2019, the growth rate has fallen to 2.1 percent, a mediocre number and a decline for which Trump presumably accepts no responsibility and blames either Nancy Pelosi, Ilhan Omar or, if he can swing it, Barack Obama. I suppose it’s natural for a president to want to take credit for everything good that happens on his (or someday her) watch, but not the blame for anything bad. Trump is more blatant about this than most. If we judge by his bad but remarkably steady approval ratings (today, according to the average maintained by 538.com, it’s 41.9 approval/ 53.7 disapproval) the pretty-good economy is not winning him new supporters, nor is his constant exaggeration of his accomplishments costing him many old ones). I already offered it above, but the full Washington Post workup of these numbers, and commentary/explanation by economics correspondent Heather Long, are here. On a related matter, if you care about what used to be called fiscal conservatism, which is the belief that federal debt and deficit matter, here’s a New York Times analysis, based on Congressional Budget Office data, suggesting that the annual budget deficit (that’s the amount the government borrows every year reflecting that amount by which federal spending exceeds revenues) which fell steadily during the Obama years, from a peak of $1.4 trillion at the beginning of the Obama administration, to $585 billion in 2016 (Obama’s last year in office), will be back up to $960 billion this fiscal year, and back over $1 trillion in 2020. (Here’s the New York Times piece detailing those numbers.) Trump is currently floating various tax cuts for the rich and the poor that will presumably worsen those projections, if passed. As the Times piece reported: