infix-notation

I'm trying to replicate, roughly, the dplyr package from R using Python/Pandas (as a learning exercise). Something I'm stuck on is the "piping" functionality. In R/dplyr, this is done using the pipe-operator %>% , where x %>% f(y) is equivalent to f(x, y) . If possible, I would like to replicate this using infix syntax (see here ). To illustrate, consider the two functions below. import pandas as pd def select(df, *args): cols = [x for x in args] df = df[cols] return df def rename(df, **kwargs): for name, value in kwargs.items(): df = df.rename(columns={'%s' % name: '%s' % value}) return df

How to calculate user given Expression in java. E:g, if the given exp is 3*4+(5*6) how to calculate this. can anyone help me out. Paulpro I found this code after a quick google: import java.util.Stack; /** * Class to evaluate infix and postfix expressions. * * @author Paul E. Davis (feedback@willcode4beer.com) */ public class InfixPostfixEvaluator { /** * Operators in reverse order of precedence. */ private static final String operators = "-+/*"; private static final String operands = "0123456789"; public int evalInfix(String infix) { return evaluatePostfix(convert2Postfix(infix)); } public

I have an associative operation >> . The problem is that its cost linearly depends on the size of its left operand. So an expression formed by a sequence of n applications of >> like a >> a >> a >> a >> a >> ... >> a it has quadratic cost in terms of n , because by default infix operators are left-associative . How to make it right-associative so that the cost of such an expression is kept linear in terms of n ? Petr Pudlák I found a solution. Scala reference says in section 6.12.3 Infix Operations : The associativity of an operator is determined by the operator’s last character. Operators

Is there a best practice for one over the other? I've been reading the Scala book by Odersky, et al. and it seems like infix is used for a lot of the Collections API functions, whereas dot is reserved for programmer-defined functions. I personally do not have any hard and fast rules for this, but I tend to use infix notation only with symbolic method names, and dot notation for alphanumeric ones. Infix notation makes it cumbersome to modify code later. Here are some examples. Imagine you have this line of code: xs filter { f } map { g } Suppose at some latter point in time you need to add a

When programming in Scala, I do more and more functional stuff. However, when using infix notation it is hard to tell when you need parenthesis and when you don't. For example the following piece of code: def caesar(k:Int)(c:Char) = c match { case c if c isLower => ('a'+((c-'a'+k)%26)).toChar case c if c isUpper => ('A'+((c-'A'+k)%26)).toChar case _ => c } def encrypt(file:String,k:Int) = (fromFile(file) mkString) map caesar(k)_ The (fromFile(file) mkString) needs parenthesis in order to compile. When removed I get the following error: Caesar.scala:24: error: not found: value map def encrypt

Challenge Here is the challenge (of my own invention, though I wouldn't be surprised if it has previously appeared elsewhere on the web). Write a function that takes a single argument that is a string representation of a simple mathematical expression and evaluates it as a floating point value. A "simple expression" may include any of the following: positive or negative decimal numbers, + , - , * , / , ( , ) . Expressions use (normal) infix notation . Operators should be evaluated in the order they appear, i.e. not as in BODMAS , though brackets should be correctly observed, of course. The