macros,lisp,common-lisp , Backquote String Interpolation

Backquote String Interpolation


Tag: macros,lisp,common-lisp

Is it possible to use lisp's macro to do string interpolation?

For instance, can I make a macro like this:

(defmacro test (a) `",a")

So that (test abc) returns "abc" as a string? I could probably cheat by quoting it and turning that quote into a string, but that doesn't work for arguments like "9:00" (without double quotes).


Lisp macros operate on arguments that have already been read by lisp's reader. Because of that a macro can't change how it's arguments are read, and if you pass an argument that will signal an error when you try to read it, e.g. 9:00 in (test 9:00), the reader signals the error before the macro even starts to run.

The reader is also customizable. Not in a way that would let you read 9:00 as "9:00" in a straightforward manner, but for example you could write a short reader macro that read @9:00 as either "9:00" or as a date object.

Edit: Something like this:

(defvar *arguments-rt* (copy-readtable ()))

(defun timestring-reader (stream char &optional count)
  (declare (ignore char count))
  (with-output-to-string (s)
    (loop repeat 4 do (write-char (read-char stream) s))))

(set-macro-character #\@ #'timestring-reader () *arguments-rt*)

(let ((*readtable* *arguments-rt*))
  (let ((args "dinner @9:00"))
    (with-input-from-string (stream args)
      (loop for arg = (read stream () ())
            while arg collect arg))))

-> (DINNER "9:00")


Append the string provided by __FUNCTION__ macro

I have defined a macro as following: #define ADD_TIME_ENTRY(_name_) m_pTimeMeasurement->addTimeEntry(_name_); Now, I want to pass the function name through ADD_TIME_ENTRY() in whichsoever function I put ADD_TIME_ENTRY() ADD_TIME_ENTRY(__FUNCTION__) works fine for me but now, I want to add "_start" or "_stop" at the end of the function name. I mean, I...

C++ / C #define macro calculation

Suppose I have #define DETUNE1 sqrt(7)-sqrt(5) #define DETUNE2 sqrt(11)-sqrt(7) And I call these multiple times in my program. Are DETUNE1 and DETUNE2 calculated every time it is called? Thanks. Please don't downvote this, I really want to know and a search didn't turn up anything definite. ...

Parentheses and macro overloading in C++

My codebase has an existing macro: #define SOME_MACRO <macro definition> For some changes I'm making, I want to add a new version of the macro that takes an argument. #define SOME_MACRO(arg1) <macro definition> I see that this question addresses selecting from multiple argument versions of a macro. However, the SOME_MACRO...

defining recursive values C

#define BLOCK_OFFSET(block) (BASE_OFFSET+(block-1)*block_size) usage lseek(fd, BLOCK_OFFSET(group->bg_inode_table)+(inode_no-1)*sizeof(struct ext2_inode),SEEK_SET); This is a fragment of a code im trying to understand and I have no idea how that definition works. Is it recursive? Can someone explain step by step whats happening in that lseek?...

in clojure, function argument type mismatch

clojure, function argument is vector, but it takes a map without problem. (defn flower-colors [colors] (str "The flowers are " (:flower1 colors) " and " (:flower2 colors))) (flower-colors {:flower1 "red" :flower2 "blue"}) ;; -> "The flowers are red and blue" Function flower-colors suppose to take vector type argument, but with...

Backquote String Interpolation

Is it possible to use lisp's macro to do string interpolation? For instance, can I make a macro like this: (defmacro test (a) `",a") So that (test abc) returns "abc" as a string? I could probably cheat by quoting it and turning that quote into a string, but that doesn't...

Defining Macros that are equal to functions that return objects in C++

So I have the singleton pattern working the way I want to, I think the main problem is something with pointers and refrences. ("..." represents irrelevent code). Universe.h ... #define TheUniverse Universe::GetInstance (); ... public: static Universe& GetInstance (); ... private: static Universe* x_instance; ... Universe.cpp ... Universe* Universe::x_instance =...

What does the non-terminating-p argument of set-macro-character do?

Set-macro-character has an optional argument called non-terminating-p. It seems to be used to indicate whether another character should be read after reading the macro character, but the reader algorithm seems to ignore this argument. Is there a difference whether I set it to true or false?

How to control C Macro Precedence

#define VAL1CHK 20 #define NUM 1 #define JOIN(A,B,C) A##B##C int x = JOIN(VAL,NUM,CHK); With above code my expectation was int x = 20; But i get compilation error as macro expands to int x = VALNUMCHK; // Which is undefined How to make it so that NUM is replaced first...

Dose VS2010 pre-calculate preprocessor defined by #define?

For Visual Studio 2010, if I define #define PI 4.0f*atan(1.0f) when PI is used somewhere later in the code, does the value needs to be calculate again or simply 3.1415926... being plugged in? Thanks. EDIT: Because I heard someone says the compiler might optimize to replace it with 3.1415926.., depending...

clojure quoting inside let

Quoting (both syntax and non-syntax) seems to fail to detect vars inside a let statement: (let [foo 1] (eval `(print foo))) This will generate an error or use whatever prior value bound was bound to foo in (def foo bar). Is there a way to make the syntax quote use...

SAS Concatenate Multiple Variables to Create Data-Driven Macro Statements

In order to keep my process data-driven, I'm trying to concatenate multiple variables, separated by comma, in order to ultimately put them in a PROC SQL list to call in multiple macro statements that would otherwise clutter my SAS pogram. Take the following sample dataset: DATA TEST; INPUT YEAR CONDITION...

Can I create a macro that unrolls loops?

I'm trying to write some fast matrix code in Rust and to do this needs to ensure that loops are unrolled. Is there a way to create a compile-time for-loop? E.g: I want unroll_loop!(f, a, 3); to generate f(a, 0); f(a, 1); f(a, 2); ...

How to share same header files between kernel modules and userspace applications.

I want to implement a simple module in which an ioctl() method is used. In the kernel module, I use kernel macros, such as _IO(), _IOWR(), etc., to define my own ioctl sub-commands. In facts, I don't care the actual values of these definitions for that I will always use...

Macro to push arguments onto stack

I've been working on a fun little project to mess around with how functions are called and I need a macro to push arguments as it'll be quite time consuming to push the arguments manually for every instance of this obfuscated call. This is my code so far: #define pushargs(...)...

Providing new version of existing macro with parameters

We have an existing log macro in our code. Lets call it LOG_XXX where XXX is the log level to use, such as LOG_INFO, LOG_DEBUG, LOG_ERROR etc. We stream log messages to the macro: LOG_INFO << "This is a log message."; Under the covers, the macro creates a temporary object...

Structuring large Lisp applications

I am currently trying to wrap my head around packages, systems & co. I now have read Packages, systems, modules, libraries - WTF? a few times, and I think I'm still having difficulties to get it right. If I simply want to split a Lisp source file into two files,...

Stata- Stopping at the variable before a specified variable in a varlist

I'm stuck on a tricky data management question, which I need to do in Stata. I'm using Stata 13.1. I have 40+ datasets I need to work on using a subset of variables that is different in each dataset. I can't include the data or specific analysis I'm doing for...

Split string in macro

I've a class name with its namespace, like BasicType::MyType. It's possible to create a macro that split the name and uses only the part after the scope operator (I want to create a MyType object in macro without the first part)? EDIT: I'm using a library with different classes in...

Why is it not advised to define macros in header files?

The Google C++ Style Guide guide advises that macros must not be defined in a .h (header) file. What are the cons of doing it?

syntax error : missing ')' before 'constant'

I have some syntax problems that I don't know how to fix. I'm trying to build some functions to matrix, can someone help me resolve those problems? 1>c:\documents and settings\one\my documents\visual studio 2010\projects\hw3\hw3\q2.c(11): error C2143: syntax error : missing ')' before 'constant' 1>c:\documents and settings\one\my documents\visual studio 2010\projects\hw3\hw3\q2.c(11): error C2143:...

EVAL/APPLY: too many arguments given to F

Hello why do i get *** - EVAL/APPLY: too many arguments given to F on function call with nested lists parameter. I cannot figure it out, since I passed a simple nested list. (defun f (L) (cond ((NULL l) nil) ((listp (car L)) (append (F(car L))) (F(cdr L) (car (F...

Understanding NASM Macro

I've come around this macro in a assembly source file and I just can't figure out how it's working. So first I come around this function (hevc_deblock.h): cglobal hevc_v_loop_filter_chroma_8, 3, 5, 7, pix, stride, tc, pix0, r3stride sub pixq, 2 lea r3strideq, [3*strideq] mov pix0q, pixq add pixq, r3strideq TRANSPOSE4x8B_LOAD...

Read input into string in Lisp reader macro

I am trying to make a reader macro that would convert @this into "this". This is what I currently have: (defun string-reader (stream char) (declare (ignore char)) (format nil "\"~a\"" (read-line stream t nil t)) ) (set-macro-character #\@ #'string-reader ) The problem is that this requires that I put a...

If strings are vectors, why are they immutable?

if strings are vectors of characters, and a vector's elements can be accessed using elt, and elt is setf-able - then why are strings immutable?

Can I create a macro or shortuct for a step of XPath in XQuery?

Do we have Macros in XQuery? If yes, could you please give an example of their usage. I have the following code let $x := //price/ancestor::* Can I someway, using macros or other things write it as follows: let $x := //price/outward So, the outward should mean ancestor::*...

Combining multiple template classes to one class using typedef

I have the following piece of code. Let us have the function declaration and implementation seperate. #include <iostream> class Y1 {}; class Y2 {}; template <class T1, class T2> class A { public: explicit A(); void foo() const; int bar() const; }; template <class T1, class T2> A<T1, T2>::A() {}...

Is there any way to skip macro replacement(During preprocessing) when macro is used as a variable name?

ConflictHeader.h #define _c 6 //This is third party header, canot change, since // there is no sorce code to rebuild testclass.h #ifndef TESTCLASS_H #define TESTCLASS_H #include <QObject> #include "ConflictHeader.h"//Include conflicted header class TestClass : public QObject { Q_OBJECT public: TestClass(QObject *parent); ~TestClass(); private: }; #endif // TESTCLASS_H testclass.cpp #include "testclass.h"...

Creating a function in compile time using a bitmap like macro

I have an ansi C function to sum up values from an array, based on patterns. Something like: long sum_all_according_to_pattern(int n, int *values, int *pattern) { long sum = 0; int i = 0; for(;i<n;i++){ if(pattern[i]) sum+=values[i]; } return sum; } Let's say I've a set of patterns such as:...

x-macro conditional error - number comparison

I would like to generate compile time error for X-macro for all X(a, b) where a > b /* X(a, b) */ #define LIST \ X(10, 20) \ X(5, 20) \ X(30, 20) \ X(1, 20) So, generate error for X(30, 20) Is this possible in C? EDIT: example usage...

create a macro in sas

I have a report that is generated once a year. each report has the form of the year inside the name - report-2011.xls, report-2012.xls etc. each report contains the following vars: ID, SAL=average monthly salary of that year, Gender (0=male, 1=female), Married (0=not married, 1=married), I need to create a...

How does this code print odd and even?

#define MACRO(num, str) {\ printf("%d", num);\ printf(" is");\ printf(" %s number", str);\ printf("\n");\ } int main(void) { int num; printf("Enter a number: "); scanf("%d", &num); if (num & 1) { MACRO(num, "Odd"); } else { MACRO(num, "Even"); } return 0; } Please explain the above code (if/else condition and how...

Insertion into a list doesn't reflect outside function whereas deletion does?

I am new to Lisp. Deletion of an item in a list by a function gets reflected outside the function but insertion doesn't. How can I do the same for insertion? For example (defun test (a b) (delete 1 a) (delete 5 b) (append '(5) b) (member '5 b)) (setq...

Extract Argument from C Macro

I have a number of definitions consisting of two comma-separated expressions, like this: #define PIN_ALARM GPIOC,14 I want to pass the second expression of those definitions (14 in the case above) to unary macros like the following: #define _PIN_MODE_OUTPUT(n) (1U << ((n) * 2U)) How can I extract the second...

Defining macro function from makefile

Suppose I have following entry in my makefile: ifeq ($(MY_DEBUG),yes) EXTRACXXFLAGS += -DMY_DEBUG=2 endif I am invoking it with make foo MY_DEBUG=yes and now I basically have #define MY_DEBUG 2 for all project files available. Question: Can I define the macro function all over the project this way, without including...

Why do I have to expose a macro implementation's 'use' in the client library?

I'm trying to use a macro I've created in a separate module. With reference to this SO question, I've imported a macro fine. However it seems that I have Update to add macro implementation #![macro_use] use std::fmt; use std::ffi::CString; use std::ffi::CStr; use std::str; extern crate libc; pub enum DbaxError...

Invalid specialized parameter in method lambda list

I am trying to write a simple coin flip program in Common Lisp. This is the code I have (defun yn (let ht (random 1) (if (eq ht 1) (princ heads) (princ tails)) ) ) It seems simple enough, but I keep getting the error: "Invalid specialized parameter in method...

Accessing argument's metadata in Clojure macro

Is there a way to retrieve the metadata of the arguments inside a clojure macro without using eval? The only thing I could come up with so far is this: (def ^{:a :b} my-var) (defmacro my-macro [s] (prn (eval `(meta (var ~s))))) (my-macro my-var) ;; Prints {:a :b, :name my-var,...

Julia: How do I create a macro that returns its argument?

My question is quite similar to this one, but with a difference. I want to create a macro (or whatever) that behaves this way: julia> @my-macro x + 2 :(x + 2) (note that x + 2 is not enclosed in quotes). Is there something like that in Julia? And...

Exceed evaluation depth when forward function in Emacs Lisp

Here is just a simplified code snipped I have not managed to work. I do not understand what is wrong. (defun enumerate-indicies (func) (let ((index 0)) (while (< index 5) (funcall func index) (setq index (1+ index))))) (defun enumerate-multiplied-indicies (func) (enumerate-indicies #'(lambda (index) (funcall func (* 10 index))))) The following...

Use Weka from ImageJ macro: 'path' is required but unset

I have tried Calling Weka from an ImageJ(Fiji) macro: run("Trainable Weka Segmentation", "open=C:\\input\\test.tif inputfile=C:\input\test.tif path=[Ljava.lang.String;@77e655d8"); But when I run that I get an error message: 'path' is required but unset This line is exactly the line I get when recording a macro and opening test.tif when the Trainable Weka Segmentation...

Common Lisp Object System method execution order

I have the following two classes: (defclass person () ()) (defmethod speak ((s person) string) (format t "-A" string)) (defmethod speak :before ((s person) string) (print "Hello! ")) (defmethod speak :after ((s person) string) (print "Have a nice day!")) (defclass speaker (person) ()) (defmethod speak ((i speaker) string) (print "Bonjour!"))...

Writing a `define-let` macro, with hygiene

I'm trying to write a define-let macro in racket, which "saves" the header of a (let ((var value) ...) ...) , namely just the (var value) ... part, and allows re-using it later on. The code below works as expected: #lang racket ;; define-let allows saving the header part of...

How to test whether an identifier that is accessible only through a #define macro is defined?

I have a #define mapping an identifier (a function name) to a new name like this: #define A doStuff This part I cannot do anything about, I have to access "A" since the actual identifier (doStuff here) may change (and this is not under my control). Now the referenced symbol...

how to apply macro on list of lines with vim

let's suppose I want to apply a macro stored on register 1 on lines: 2, 5, 9 but without applying on lines in between. I saw that you can give a range but that is not what I want. I've tried some variation on :2, 5, 9 @1 without success

Unexpected output printf statement [duplicate]

This question already has an answer here: Why is ā€œiā€ variable getting incremented twice in my program? 8 answers Why outputs of i and j in the following two printf()s are different? #include <cstdio> #define MAX(x,y) (x)>(y)?(x):(y) int main() { int i=10,j=5,k=0; k==MAX(i++,++j); printf("%d %d %d\n",i,j,k); i=10,j=5,k=0; k=MAX(i++,++j); printf("%d...

Python-like C++ decorators

Are there ways to decorate functions or methods in C++ like in python style? @decorator def decorated(self, *args, **kwargs): pass Using macros for example: DECORATE(decorator_method) int decorated(int a, float b = 0) { return 0; } or DECORATOR_MACRO void decorated(mytype& a, mytype2* b) { } Is it possible?...

Why is my C code printing out an extra line of rows?

#include <stdio.h> #define rows 500 //can define rows as any number int main() { int i,j; for(i=0;i<=rows;++i) { for(j=0;j<(2*i+1);++j) { printf("* "); } printf("\n"); } return 0; } So here is my code, what it does is it prints the number of rows set by #define and creates a right...

Why don't I get a warning when I declare a variable with same name in a macro that already exists in a function?

Playing with a macro and thought about the following scenario. Declaring variable in a macro which already exists in function from which this macro has been called, why compiler doesn't complain. When I declare in a code a variable it give me a warning: Redefinition of 'temp' I think that...