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Re: [boost] Vector with compile-time polymorphism
by Ivica B 11 Apr '21

11 Apr '21

Yes, I guess it is very similar (if not the same) to polly_collection, or more specifically to: boost::any_collection. Is there a data structure that is similar to polly_collection but can be sorted? On Fri, Apr 9, 2021 at 2:47 PM Ivica B via Boost <boost(a)lists.boost.org> wrote: > multivector<rectangle, circle, triangle> mvect; > Each type is held in a separate std::vector for that type. So in the above > case, multivector<rectangle, circle, triangle> consists of three > std::vectors: std::vector<rectangle>, std::vector<circle> and > std::vector<triangle>. > Sounds a bit like https://www.boost.org/doc/libs/1_75_0/doc/html/poly_collection.html no? --DD

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[GSOC2021][Boost.uBLAS][Draft Proposal]Create new matrix and vector types
by Mr. Cell 11 Apr '21

11 Apr '21

Create new matrix and vector types This is with reference to the communication and as advised by my mentor (Mr. Amit Singh). I am hereby attaching my draft project proposal for boost::uBlas for review and suggestions if any. https://docs.google.com/document/d/1SXB9r_3dbgD0kT5xNmFzQ5mD0FuvTO0Y5TOkdyr… Thanks & Regards.

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[release] Boost 1.76.0 Release Candidate 1
by Marshall Clow 11 Apr '21

11 Apr '21

IMPORTANT NOTE: This will be the last RC posted on BinTray! The first release candidates for the 1.76.0 release are now available at: <https://dl.bintray.com/boostorg/release/1.76.0/source/> The SHA256 checksums are as follows: aaf920e31ae815ff6b55d70a28bb614a6aa6f5cd2f6e4543461d20a4fe39df4e boost_1_76_0_rc1.7z 5dd0c91e1f0f18d452fcaa772d9c30815e449dd4fe99fadf224cca180d98cee3 boost_1_76_0_rc1.zip 5b9844335bc327272030b8050cf417178d26c8abbc64ed7aefc4d818facc1c10 boost_1_76_0_rc1.tar.gz cea1cf7609daf5bb285a625530e8d660dca51816007da7f5eb3f577b685a888d boost_1_76_0_rc1.tar.bz2 As always, the release managers would appreciate it if you download the candidate of your choice and give building it a try. Please report both success and failure, and anything else that is noteworthy. -- The Release managers

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The descriptor does not fit into the select call's fd_set
by George Nistor 10 Apr '21

10 Apr '21

Hi all, I am having a problem with the following error message '' The descriptor does not fit into the select call's fd_set" The setup I have is QNX , VSomeIP lib (socket abstractisation lib) , lib Boost 1.61 (a very old version) I get the error in this lib VSomeIp from the bellow boost call. The call to boost::asio::async_write(3 params) gives the above error message. I have tried to see also on QNX with > pidin -p vsomeip fds How many open file descriptor do I have and I got value 123. As far as I know there is a limitation 1024 of open file descriptors. Could you provide some help? Does the latest boost lib solve this particular case? I appreciate any suggestion, Also please say if any info is missing Thanks George Nistor

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Vector with compile-time polymorphism
by Ivica B 09 Apr '21

09 Apr '21

Hi! I am doing a performance C++ work and there is a data structure that we use and I think it is very useful even for the general public. Here is the description: Currently, I call it *multivector* (I know there is a data structure with the same name, this is a temporary name). It works like this: You specify all the types you want to hold in your multivector: multivector<rectangle, circle, triangle> mvect; Each type is held in a separate std::vector for that type. So in the above case, multivector<rectangle, circle, triangle> consists of three std::vectors: std::vector<rectangle>, std::vector<circle> and std::vector<triangle>. Now, the magic happens when we use templates to process all three vectors at once. Imagine there is a function *draw* for all three types. We can do something like this: mvect.for_each([&](auto& shape) { shape.draw(bitmap); }); The above code generates three for_each loops, for rectangle, circle and triangle. Inside the loops it calls the draw method for each type. There is no dispatching inside the loops, and the loops are really easy for the compiler to optimize (due to their simplicity). Prototype implementation: https://github.com/ibogosavljevic/johnysswlab/blob/master/2021-02-virtualfu… Advantages over std::vector<std::variant>>: * Uses less memory (std::variant uses the amount of memory per element that is big enough to store the biggest type) * Is more optimal: each type generates its own processing loop, there is no dispatching code inside the loop. The compilers vectorized these loops easier. Downsides: * You cannot sort the elements in the whole vectors (even though you can sort them in individual containers) * Code bloat (many types can create a lot of code, this is the case with std::vector<std::variant>> too) Please let me know what you think. Ivica

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GSoC proposal review
by Aditya Tiwari 09 Apr '21

09 Apr '21

Hello all, I'm Aditya Tiwari, a GSoC aspirant. I've submitted my proposal for Boost GIL (generic image library) on GSoC's website under boost. I would be grateful if someone review's my proposal and give me suggestions if needed. I've shared the doc link of my proposal with commenter rights. Thanks and Regards, Aditya Tiwari

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Request to review my proposal
by Pratik Awasthi 08 Apr '21

08 Apr '21

Hello Mentor, I Pratik Awasthi request you to review my GSOC 2021 proposal and do suggest updates https://docs.google.com/document/d/1eeuXx4x2birJXxQChEUnBrLbWTzKd8oc9UspeYU…

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[GSoC'21]Seeking Review of draft Proposal for Project 3: Finalize DataFrame Implementation
by Kowndinya Renduchintala 08 Apr '21

08 Apr '21

Hello everyone! I am Kowndinya Renduchintala, a second Year Undergrad in Computer Science and Engineering Department at Indian Institute of Technology Bombay(IIT Bombay). TO THE COMMUNITY: In short, this project’s end goal is to add to the dataframe implementation of GSoC’19, inspired from R, Python and others. This already has features like constructing a column of data frame, the data frame itself in a couple of ways and also supports operations like select, join etc. My main focus is on adding features that are most desired by a data scientist working with REAL WORLD data and I have added some such possible features in the draft linked below. I have never been into Open Source Software Development before. I would like to make this first attempt of mine a success and I hence seek for advice from anyone willing to spare time, to improve upon my list of deliverables, for establishing the foundation of Boost.uBlas as a new data science library. TO THE MENTOR(David): My progress so far: I have glanced through the GSoC’19 implementation, and referred to some pandas docs to make this draft. I am actually a bit worried because I was too late at completing my Competency test and contacting you, the main reason being a very hectic coursework of mine. The only remaining things are – Modifying the README.md for GitHub Actions Usage and some basic error handling in the code. I have shared the draft in the Google’s portal which also contains a link to my forked repository of ublas, containing my solutions to the competency test. I will also be completing the remaining things(possibly also improve small parts like updating naïve matrix multiplication to Strassen’s) in about 2 days. Also, I want to have a little chat with you as I found out that you were the mentor for this project in 2019 and you might be having some pre-conceived ideas on improving the current implementation, from your previous interaction. Please let me know what you think… Here is the link to my proposal draft : https://drive.google.com/file/d/1cnSrrOWfbteJKlmGxiIY9R5H_-YSkb-n/view? usp=sharing Cheers, Kowndinya

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regarding submission of my first proposal
by amit kumar 08 Apr '21

08 Apr '21

Hello i am Amit kumar. I am currently in third year of undergraduate bachelor's degree program , my field of study is Information Technology.I really curious about open source development and i always support open source software , but i have never contributed to any open source project . I have intermediate level command on c++ and i am doing competitive programming from my first year two and half year from now this is my codeforces <https://codeforces.com/profile/stream_cipher> and codechef <https://www.codechef.com/users/ammitkumar> profile link. I am very beginner to the field of software development but i know some website development . I really want to contribute to the Boost C++ library but i don't have any idea about how to submit the first proposal and how to select the topic on which i should work on please suggest me the path way. waiting for your reply. Thaks :)

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[Boost] [Lambda2] Review starts Monday March 22, 2021 to March 31, 2021
by Joel de Guzman 08 Apr '21

08 Apr '21

The Boost formal review of the Lambda2, authored by Peter Dimov, starts Monday, March 22, 2021 to March 31, 2021 (inclusive). Documentation: https://pdimov.github.io/lambda2/doc/html/lambda2.html Source: https://github.com/pdimov/lambda2/ Lambda2 is a simple, but functional, C++14 lambda library. It takes advantage of the fact that the standard <functional> header already provides placeholders _1, _2, _3, and so on, for use with std::bind, and function objects such as std::plus, std::greater, std::logical_not, and std::bit_xor, corresponding to arithmetic, relational, logical and bitwise operators. Please provide in your review information you think is valuable to understand your choice to ACCEPT or REJECT including Lambda2 as a Boost library. Please be explicit about your decision (ACCEPT or REJECT). Some other questions you might want to consider answering: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With which compiler(s)? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? More information about the Boost Formal Review Process can be found at: http://www.boost.org/community/reviews.html The review is open to anyone who is prepared to put in the work of evaluating and reviewing the library. Prior experience in contributing to Boost reviews is not a requirement. Thank you for your efforts in the Boost community. They are very much appreciated. Peter is often available in the CppLang Slack #boost channel should you require any clarification not covered by the documentation. I am not frequently available in the Slack channel, but I'll certainly pay attention to the discussions. Please don't hesitate to ping me if needed. Cheers, --Joel de Guzman

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FFT proposal for gsoc 2021
by Eduardo Quintana 08 Apr '21

08 Apr '21

Hi Boost community, I've been working on a C++ templated library for Fast Fourier Transforms, https://github.com/Lagrang3/fftx. Templated because some FFT algorithms are algebraic-field independent, eg. you could FFT an array of N matrices provided a Nth matrix-root-of-unity is given. As a result you could have a single algorithm for a variety of underlying, eg. `std::complex<float>`, `std::complex<double>`, `std::complex<long double>`, `boost::math::quaternion`, finite field types (this would yield the "Number theoretic transform" https://cp-algorithms.com/algebra/fft.html#toc-tgt-6) I would like to improve this library during the GSOC 2021, as a proposal for inclusion inside Boost.Math or Boost.Algorithms. Is there anyone interested in supervising this project? Any opinions? Best regards, Eduardo Quintana

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[GSoC 2021] Proposal for Boost.xml
by qiqi tang 07 Apr '21

07 Apr '21

Hello, My name is Fuqi Tang who is a graduate student in China. I am majoring in Software engineering. I want to take part in GSoC 2021 for the Boost.xml project and I will really appreciate it if the community can watch my proposal and give me some advice to improve it. Below is my proposal link https://docs.google.com/document/d/1GYuiVqU8ChaTG2RO2qhQbpF9QSuK5uGRRNDx0M2… Thanks a lot! Regards, Fuqi

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Review and Feedback for Boost.XML proposal
by YAGNIK VAGHELA 07 Apr '21

07 Apr '21

Hello, I am Yagnik Vaghela. I live in India. I am a 3rd year undergraduate student pursuing B.tech in ICT(Information and communication Technology) at DA-IICT. I would like to participate in GSoC this year. I would like to work on a project Boost.XML library. Here's my draft proposal. Please kindly review it and give feedback. any suggestions would be appreciated. https://docs.google.com/document/d/14rzb_3W_5lNM5_qfYpV4zVOh3QmOwuQgWLfeem_…

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[GSoC] Boost.Real GSoC Proposal Feedback
by Divyam Singal 07 Apr '21

07 Apr '21

Hi all, This is Divyam, a 2nd year CSE student at IIT Guwahati. I have shared my draft proposal through GSoC website. I have shared the drive link to the pdf, as docs don't support rendering of LaTeX maths and graphs. You can comment to provide review by right-clicking that portion in the pdf. Do have a look at it and provide the feedback so that I can make the necessary changes. Thanks and Regards, Divyam Singal

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boost mailing list archive stopped updating
by Janek Kozicki 07 Apr '21

07 Apr '21

Just a heads-up, boost mailing list archive stopped updating 3 days ago: https://lists.boost.org/Archives/boost/ best regards Janek -- Janek Kozicki, PhD. DSc. Arch. Assoc. Prof. Gdańsk University of Technology Faculty of Applied Physics and Mathematics Department of Theoretical Physics and Quantum Information -- http://yade-dem.org/ http://pg.edu.pl/jkozicki (click English flag on top right)

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[Boost][GIL][GSOC21]Review and Feedback for Boost GIL project proposal
by sayan chaudhuri 07 Apr '21

07 Apr '21

Hello Everyone, My name is Sayan Chaudhuri. I am a final year,undergraduate student,in the Computer Science and Engineering department of IEM,India . I am eager to participate in the GSOC 2021 and willing to contribute to the Boost GIL library. I am looking to implement the ORB feature descriptor for BOOST GIL . Currently the only keypoint detector present is Harris Corner. And no separate descriptors are present. ORB comes with both a keypoint detector and descriptor bundled and it is suitable for real time systems and also license free. Feature descriptors are important for tasks like object recognition, structure from motion, image stitching etc. And ORB is a good choice for real time systems. I am attaching the link of my project proposal for the same below. I would request anyone who is interested to mentor me or co-mentor to kindly have a look at my proposal. I would really appreciate any feedback from your side and I am looking to continue the discussion of the project further. Proposal link : https://docs.google.com/document/d/1ARL57qRdNWPGe3GlqY1n8E31LyUCvyIyvBk_agz… Thank you.

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[release] 1.76.0 post-beta merges
by Marshall Clow 06 Apr '21

06 Apr '21

The master branch is is now open for post-beta merges, but only as described in the Post-Beta Merge Policy. See <https://github.com/boostorg/boost/wiki/Releases%3A-Beta-Merge-Policy> Reminder: The master branch closes for the release on Wednesday, Apr 7. Full calendar here: https://www.boost.org/development/ <https://www.boost.org/development/> — Marshall P.S Doc changes and test changes do NOT require release manager approval to be merged.

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[gsoc21] Feedback and advice on proposal
by Haoran Xu 04 Apr '21

04 Apr '21

Hi, I'm really interested in applying for GSoC 2021 and implementing the Boost.XML library. I have completed the competency test and have drafted by proposal. https://docs.google.com/document/d/1KP-g1zMXQdqUzSFMtsURcSpZisjjspvX8lRkdRj… Please tell me what you think this proposal is missing and what I should add on. It's my first time applying for GSoC so I'm not very familiar with the process. Thank you!

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Re: [boost] [Boost][GIL][GSOC21] Draft Proposal for Boost GIL
by sayan chaudhuri 04 Apr '21

04 Apr '21

Hello Everyone, My name is Sayan Chaudhuri. I am a final year,undergraduate student,in the Computer Science and Engineering department of IEM,India . I am eager to participate in the GSOC 2021 and willing to contribute to the Boost GIL library. I am looking to implement the ORB feature descriptor for BOOST GIL . Currently the only keypoint detector present is Harris Corner. And no separate descriptors are present. ORB comes with both a keypoint detector and descriptor bundled and it is suitable for real time systems and also license free. Feature descriptors are important for tasks like object recognition, structure from motion, image stitching etc. And ORB is a good choice for real time systems. I am attaching the link of my project proposal for the same below. I would request anyone who is interested to mentor me or co-mentor to kindly have a look at my proposal. I would really appreciate any feedback from your side and I am looking to continue the discussion of the project further. Proposal link : https://docs.google.com/document/d/1ARL57qRdNWPGe3GlqY1n8E31LyUCvyIyvBk_agz… . Thank you.

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Re: [boost] FFT proposal for gsoc 2021
by Eduardo Quintana 03 Apr '21

03 Apr '21

Hi Kostas, Good critics are necessary for the sake of improvement. All of your comments are welcome. > 1) The discussion of NTT. While boost.multiprecision can potentially be used > to implement the Zp ring, it currently does not contain any such construct. > Reading further, there is nothing about NTT in the deliverables. If the idea > is peripheral to the GSOC project, then it does not need to be mentioned at > all. Note that even the PARI library does not yet have NTT implemented and > for them I think it is a high priority (must be a very hard problem). 1) I mentioned the NTT because is part of the motivation for having a general DFT instead just complex-DFT. Maybe the text it is not clear. You'll get the NTT for free. See these two examples https://github.com/Lagrang3/fftx/blob/master/examples/ex02.cpp https://github.com/Lagrang3/fftx/blob/master/examples/ex03.cpp Unfortunately I haven't produced a convolution routine yet, hence in ex03 I had to compute it explicitely. There is also a small implementation of Zp https://github.com/Lagrang3/fftx/blob/master/examples/modulo.h if there was one in Boost I would gladly use it. > 2) Section 2.2. Most people know the Convolution Theorem, but at least myself > do not know anything about the Rader algorithm. Since you propose to > implement it, why not describe it in that Section, maybe instead of the > Convolution Theorem. 2) The Convolution Theorem is very well known yes. I wanted just to make a small subsection in order to clarify which flavour of the Convolution I am using: the Circular Discrete Convolution (CDC) which fits naturally into the DFT scheme. The other Discrete Convolution is the one that you write as c_i = \sum_{j} a_j b_{i-j} produces, in my opinion, many questions to the reader for instance: what do we do with the negative indexes? Zero-pad them or wrap around from the end? I think writing proofs and detailed algorithms is not necessary for the text of the proposal. Last year when I started the fftx experiment I came to the conclusion at some point that I needed, besides Cooley-Tukey and mixed-radix, another algorithm to compute the DFT for prime sizes. Then I found the description of Rader's algorithm in Wikipedia. FFTW uses it, by the way. > 3) Section 2.3. You say: "FFTW was designed to compute DFT for complex > numbers, like in Example 1. There is no support for DFT in the broader sense > of Definition 1. For example, we cannot use FFTW to compute the NTTs described > in the Example 2." Since you are not going to be able to solve this problem in > this GSOC project, it is better to not make such comments. 3) Yes I will solve that problem. There will be two back-ends: mine for general purposes DFTs and FFTW for complex DFTs. My back-end is half-way through I have implemented: - two versions of the mixed-radix Cooley-Tukes (aka Good-Thomas) recursively and not, - a pure Cooley-Tukey in-place which is the one in the blue line shown here: https://github.com/Lagrang3/fftx/blob/master/assets/powers-2.png That makes the back-end functional for any DFT size, with the inconvenience of the O(n^2) slow-down for prime numbers. The work to be done from now on will include the Rader algorithm (for the prime case) and further performance improvements. A funny thing about this general purpose DFT back-end is that I can test its performance against other complex-DFT (eg. FFTW). If some knows of a NTT library or the implementation of weirder DFTs to compare with, please raise your hand. > 4) Section 2.3. "scalability of the parallel MPI routines for computing > 3-dimensional DFT" , "domain decomposition" - here again I think it is worth > to remember that if the project is not going to address domain decomposition, > then it is better to not talk about it. 4) That's true. But that's a very urgent problem that we could very well solve originally within Boost. However it cannot be done until we produce a Boost FFT. Hence you get an extra motivation for doing the Boost FFT. > 5) Since this project is done under Boost, it seems logical to make sure the > proposed code work with Boost.Math complex types. Is this not part of the > plan? Why no word about it in the deliverables? 5) It did cross my mind, but I clearly forgot to talk about it. Thanks for alerting me. Thanks for the feedback. Eduardo

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[lambda2] Andrzej's review
by Andrzej Krzemienski 02 Apr '21

02 Apr '21

Hi Everyone, I recommend to REJECT Boost.Lambda2 library in its current form. My opinion is not very strong, and it is based on the perceived trade-off between usefulness and technical problems. I acknowledge that there are practical use cases that the library can address, that are not provided in documentation. (I recommend that examples with pointers, and maybe a complex one with column-oriented design be added). I consider the ADL issue that Barry pointed out a serious one. This will be an additional place where users would suddenly be caught by a magical problem that they will spend hours understanding. I think that the main problem here is that Boost.Lambda2 defines the operators that should belong to namespace std::placeholders. I also note that if this was added to the Standard Library, the problem would be nonexistent, because they would reside in namespace std. Could I propose an alternative design. Add placeholders _1, _2, ... into namespace `boost::lambda2::placeholders` specialize std::is_placeholder` for them, so that `std::bind` can recognize them. Add operators in the same namespace. Then, recommend the following usage of the library: ``` using namespace boost::lambda2::placeholders; void fun() { auto pred = std::bind(_1, &Employee::name) == std::bind(_2, &Employee::name); } ``` This single using directive would make both `std::bind` and Boost.Lambda2 operators work. I would find such a library acceptable. And in fact I could make it a condition for a conditional acceptance. Now, the standard questions: > - What is your evaluation of the design? > I object to the choice to add operators for placeholders from one namespace (std::placeholders) into another namespace (boost::lambda2). Save for that, I find anything else good. - What is your evaluation of the implementation? > Very sweet and clean. I only expect other operators to also work. But Peter already explained that this is his plan. - What is your evaluation of the documentation? > This library doesn't require much documentation of the interface. But I fill it is missing the Motivation section. I would expect to see practical examples: not long ones, but ones that I will find in real programs, like dealing with pointers. - What is your evaluation of the potential usefulness of the library? > Others have convinced me that it will find sufficient application in real programs. - Did you try to use the library? With which compiler(s)? Did you > have any problems? > I tried to reimplement it, and played with some toy examples in Wandbox. (newest GCC). It worked fine. - How much effort did you put into your evaluation? A glance? A quick > reading? In-depth study? > I was able to reimplement it, read the entire implementation (which was not difficult: it is like seventy lines). I spent like three hours in total studying it. - Are you knowledgeable about the problem domain? > I used Boost.Lambda and Boost.Bind in the past. Finally, I would like to thank Peter for writing and sharing this library. Regards, &rzej;

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Idea Suggestion for GsOC'21
by Sanyam Bhaskar 01 Apr '21

01 Apr '21

Hey! This is Sanyam Bhaskar. I read over the default Ideas provided to us and XML Parser really caught my eye. I would like to contribute to the same but don’t know where to start. Also, as per my understanding, XML is relatively outdated , when compared to data languages like JSON. So in addition to this being an XML Parser, I think adding a JSON parser alongside it would boost the library’s utility in the modern day industry. I Would appreciate it if someone could tell me how to get started and some feedback on the suggestion. Looking forward to contributing to the project. Yours, Sanyam Bhaskar

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[range] the strange behavior of adjacent_filter
by Andrzej Krzemienski 31 Mar '21

31 Mar '21

Hi everyone, Boost.Range has two GitHub issues on the strange behavior of adjacent_find that have been sitting there for more than two years: https://github.com/boostorg/range/issues/80 https://github.com/boostorg/range/issues/81 The behavior of the algorithm is not well described, but the intuitive expectation would be that it returns for every pair of adjacent elements that match the predicate the second of the pair. However, the unexpected behavior of the algorithm is that for a non-empty range it literally always returns the first element. I do not think that this is by accident, because Ranges V3 also expose the same behavior: https://godbolt.org/z/P33j1qvT6 Does anyone happen to know the reasoning or motivation behind this behavior? Regards, &rzej;

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Interested in creating new matrix and vector types
by Gagandeep Bhatia 31 Mar '21

31 Mar '21

Hey, I'm Gagandeep Bhatia, currently pursuing the 2nd year in Christ University, Bangalore, India. You can reach me at gagandeepbhatia2303(a)gmail.com or +919466935025. I went through your upcoming projects on Google Summer of Code, your idea on creating new matrix and vector types is really impressive. The best part about your project is It supports all matrix sizes, from small fixed-size matrices to arbitrarily large dense matrices, and even sparse matrices. It supports all standard numeric types, including std::complex, integers, and is easily extensible to custom numeric types. It supports various matrix decompositions and geometry features I truly want to become part of this project for a better mutual achievement, in the past I have done a few projects, which will help me to contribute my best in this project. It will be really kind if you can share some more details about your project, so I learn more about your project. with regards.

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Boost.Lambda2 usage
by Barry Revzin 31 Mar '21

31 Mar '21

Hey all, I spent this morning implementing views::zip using Boost.Lambda2 (because views::zip requires writing lots of single-operator lambdas, so it fits the problem quite well). You can see the implementation here: https://godbolt.org/z/jcjdd3xeo I ran into a few issues I wanted to point out. First, several operators are missing. This is the standard library's fault (it's weird that not even dereference is there). But if the standard library isn't going to provide them, I figure Boost.Lambda2 should, since these are probably going to come up so may as well just add a few more lines of code and call it a day. I needed to define five: * (unary), ++ and -- (prefix), +=, and -=. Second, this library has name lookup issues. Here's a reduced example ( https://godbolt.org/z/z8oEqnTnG) #include < https://raw.githubusercontent.com/pdimov/lambda2/develop/include/boost/lamb… > namespace N { struct Irrelevant { }; void operator+(Irrelevant, Irrelevant); int plus_one(int i) { using namespace boost::lambda2; return (_1 + 1)(i); } } This doesn't compile. _1 + 1 finds the appropriately-named irrelevant operator+ and stops there, and we never get to the operator+ in namespace boost::lambda2. Either the operators need to be put in namespace std::placeholders for ADL (which seems naughty, but also seems like something the standard library could potentially do?) or the library should provide its own placeholders. That would lose the nice _1 name, but gain the ability to provide both [] and (). Thanks for the library, Barry

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