Some implementations support additional features. For example, Kawa and JScheme provide integration with Java classes, and the Scheme to C compilers often make it easy to use external libraries written in C, up to allowing the embedding of actual C code in the Scheme source. Another example is Pvts, which offers a set of visual tools for supporting the learning of Scheme.

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Some implementations support additional features. For example, Kawa and JScheme provide integration with Java classes, and the Scheme to C compilers often make it easy to use external libraries written in C, up to allowing the embedding of actual C code in the Scheme source. Another example is Pvts, which offers a set of visual tools for supporting the learning of Scheme.

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Scheme is a very simple language, much easier to implement than many other languages of comparable expressive power.[18] This ease is attributable to the use of lambda calculus to derive much of the syntax of the language from more primitive forms. For instance of the 23 s-expression-based syntactic constructs defined in the R5RS Scheme standard, 14 are classed as derived or library forms, which can be written as macros involving more fundamental forms, principally lambda. As R5RS says (R5RS sec. 3.1): "The most fundamental of the variable binding constructs is the lambda expression, because all other variable binding constructs can be explained in terms of lambda expressions."[4]

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Similar procedures are provided for input. R5RS Scheme provides the predicates input-port? and output-port?. For character input and output, write-char, read-char, peek-char and char-ready? are provided. For writing and reading Scheme expressions, Scheme provides read and write. On a read operation, the result returned is the end-of-file object if the input port has reached the end of the file, and this can be tested using the predicate eof-object?.

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The R6RS standard has caused controversy because it is seen to have departed from the minimalist philosophy.[13][14] In August 2009, the Scheme Steering Committee, which oversees the standardization process, announced its intention to recommend splitting Scheme into two languages: a large modern programming language for programmers; and a small version, a subset of the large version retaining the minimalism praised by educators and casual implementors.[7] Two working groups were created to work on these two new versions of Scheme. The Scheme Reports Process site has links to the working groups' charters, public discussions and issue tracking system.

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Similar procedures are provided for input. R5RS Scheme provides the predicates input-port? and output-port?. For character input and output, write-char, read-char, peek-char and char-ready? are provided. For writing and reading Scheme expressions, Scheme provides read and write. On a read operation, the result returned is the end-of-file object if the input port has reached the end of the file, and this can be tested using the predicate eof-object?.

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Continuations in Scheme are first-class objects. Scheme provides the procedure call-with-current-continuation (also known as call/cc) to capture the current continuation by packing it up as an escape procedure bound to a formal argument in a procedure provided by the programmer. (R5RS sec. 6.4)[4] First-class continuations enable the programmer to create non-local control constructs such as iterators, coroutines, and backtracking.

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Some implementations support additional features. For example, Kawa and JScheme provide integration with Java classes, and the Scheme to C compilers often make it easy to use external libraries written in C, up to allowing the embedding of actual C code in the Scheme source. Another example is Pvts, which offers a set of visual tools for supporting the learning of Scheme.

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The R5RS standard specifies procedures exact->inexact and inexact->exact which can be used to change the exactness of a number. inexact->exact produces "the exact number that is numerically closest to the argument". exact->inexact produces "the inexact number that is numerically closest to the argument". The R6RS standard omits these procedures from the main report, but specifies them as R5RS compatibility procedures in the standard library (rnrs r5rs (6)).

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Invocations of macros and procedures bear a close resemblance—both are s-expressions—but they are treated differently. When the compiler encounters an s-expression in the program, it first checks to see if the symbol is defined as a syntactic keyword within the current lexical scope. If so, it then attempts to expand the macro, treating the items in the tail of the s-expression as arguments without compiling code to evaluate them, and this process is repeated recursively until no macro invocations remain. If it is not a syntactic keyword, the compiler compiles code to evaluate the arguments in the tail of the s-expression and then to evaluate the variable represented by the symbol at the head of the s-expression and call it as a procedure with the evaluated tail expressions passed as actual arguments to it.

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R5RS resolves this confusion by specifying three procedures that return environments and providing a procedure eval that takes an s-expression and an environment and evaluates the expression in the environment provided. (R5RS sec. 6.5)[4] R6RS extends this by providing a procedure called environment by which the programmer can specify exactly which objects to import into the evaluation environment.

Scheme is primarily a functional programming language. It shares many characteristics with other members of the Lisp programming language family. Scheme's very simple syntax is based on s-expressions, parenthesized lists in which a prefix operator is followed by its arguments. Scheme programs thus consist of sequences of nested lists. Lists are also the main data structure in Scheme, leading to a close equivalence between source code and data formats (homoiconicity). Scheme programs can easily create and evaluate pieces of Scheme code dynamically.

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Want to buy supplies for a church start-up in Africa? Take a Work & Witness trip to Quito? Collect Crisis Care Kits? Your participation in Mission Specials and Ten Percent Projects is a valued part of our mission heritage. We recognize that together we achieve much more than any individual church could alone. The Church of the Nazarene is a connectional church - from MAC Norte to Norway and from Nairobi to Nebraska - churches supporting churches!

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Most Lisps specify an order of evaluation for procedure arguments. Scheme does not. Order of evaluation—including the order in which the expression in the operator position is evaluated—may be chosen by an implementation on a call-by-call basis, and the only constraint is that "the effect of any concurrent evaluation of the operator and operand expressions is constrained to be consistent with some sequential order of evaluation." (R5RS sec. 4.1.3)[4]

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In economics funds are injected into the market as capital by lenders and taken as loans by borrowers. There are two ways in which the capital can end up at the borrower. The lender can lend the capital to a financial intermediary against interest. These financial intermediaries then reinvest the money against a higher rate. The use of financial intermediaries to finance operations is called indirect finance. A lender can also go the financial markets to directly lend to a borrower. This method is called direct finance.[3]

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Scheme is primarily a functional programming language. It shares many characteristics with other members of the Lisp programming language family. Scheme's very simple syntax is based on s-expressions, parenthesized lists in which a prefix operator is followed by its arguments. Scheme programs thus consist of sequences of nested lists. Lists are also the main data structure in Scheme, leading to a close equivalence between source code and data formats (homoiconicity). Scheme programs can easily create and evaluate pieces of Scheme code dynamically.

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Entrepreneurs with a business concept would want to accumulate all the necessary resources including capital to venture into a market. Funding is part of the process, as some businesses would require large start-up sums that individuals would not have.[5] These start-up funds are essential to kick-start a business idea, without it, entrepreneurs would not have the ability to carry out their concepts in the business world.

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Crowdfunding exists in mainly two types, reward-based crowdfunding and equity-based crowdfunding. In the former, small firms could pre-sell a product or service to start a business whereas in the latter, backers buys certain amount of shares of a firm in exchange of money.[8] As for reward-based crowdfunding, project creators would set a funding target and deadline. Anyone who is interested can pledge on the projects. Projects must reach its targeted amount in order for it to be carried out. Once the projects ended with enough funds, projects creators would have to make sure that they fulfil their promises by the intended timeline and delivery their products or services.[9]

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In economics funds are injected into the market as capital by lenders and taken as loans by borrowers. There are two ways in which the capital can end up at the borrower. The lender can lend the capital to a financial intermediary against interest. These financial intermediaries then reinvest the money against a higher rate. The use of financial intermediaries to finance operations is called indirect finance. A lender can also go the financial markets to directly lend to a borrower. This method is called direct finance.[3]

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Want to buy supplies for a church start-up in Africa? Take a Work & Witness trip to Quito? Collect Crisis Care Kits? Your participation in Mission Specials and Ten Percent Projects is a valued part of our mission heritage. We recognize that together we achieve much more than any individual church could alone. The Church of the Nazarene is a connectional church - from MAC Norte to Norway and from Nairobi to Nebraska - churches supporting churches!

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Entrepreneurs with a business concept would want to accumulate all the necessary resources including capital to venture into a market. Funding is part of the process, as some businesses would require large start-up sums that individuals would not have.[5] These start-up funds are essential to kick-start a business idea, without it, entrepreneurs would not have the ability to carry out their concepts in the business world.

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Scheme's input and output is based on the port datatype. (R5RS sec 6.6)[4] R5RS defines two default ports, accessible with the procedures current-input-port and current-output-port, which correspond to the Unix notions of standard input and standard output. Most implementations also provide current-error-port. Redirection of input and standard output is supported in the standard, by standard procedures such as with-input-from-file and with-output-to-file. Most implementations provide string ports with similar redirection capabilities, enabling many normal input-output operations to be performed on string buffers instead of files, using procedures described in SRFI 6.[30] The R6RS standard specifies much more sophisticated and capable port procedures and many new types of port.

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The elegant, minimalist design has made Scheme a popular target for language designers, hobbyists, and educators, and because of its small size, that of a typical interpreter, it is also a popular choice for embedded systems and scripting. This has resulted in scores of implementations,[35] most of which differ from each other so much that porting programs from one implementation to another is quite difficult, and the small size of the standard language means that writing a useful program of any great complexity in standard, portable Scheme is almost impossible.[7] The R6RS standard specifies a much broader language, in an attempt to broaden its appeal to programmers.

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The reliance on lists as data structures is shared by all Lisp dialects. Scheme inherits a rich set of list-processing primitives such as cons, car and cdr from its Lisp progenitors. Scheme uses strictly but dynamically typed variables and supports first class procedures. Thus, procedures can be assigned as values to variables or passed as arguments to procedures.

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Funding is the act of providing financial resources, usually in the form of money, or other values such as effort or time, to finance a need, program, and project, usually by an organization or company. Generally, this word is used when a firm uses its internal reserves to satisfy its necessity for cash, while the term financing is used when the firm acquires capital from external sources.[1]

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A feature of R6RS is the record-type descriptor (RTD). When an RTD is created and used, the record type representation can show the memory layout. It also calculated object field bit mask and mutable Scheme object field bit masks, and helped the garbage collector know what to do with the fields without traversing the whole fields list that are saved in the RTD. RTD allows users to expand the basic RTD to create a new record system.[11]

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Invocations of macros and procedures bear a close resemblance—both are s-expressions—but they are treated differently. When the compiler encounters an s-expression in the program, it first checks to see if the symbol is defined as a syntactic keyword within the current lexical scope. If so, it then attempts to expand the macro, treating the items in the tail of the s-expression as arguments without compiling code to evaluate them, and this process is repeated recursively until no macro invocations remain. If it is not a syntactic keyword, the compiler compiles code to evaluate the arguments in the tail of the s-expression and then to evaluate the variable represented by the symbol at the head of the s-expression and call it as a procedure with the evaluated tail expressions passed as actual arguments to it.

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In the R5RS standard and also in later reports, the syntax of Scheme can easily be extended via the macro system. The R5RS standard introduced a powerful hygienic macro system that allows the programmer to add new syntactic constructs to the language using a simple pattern matching sublanguage (R5RS sec 4.3).[4] Prior to this, the hygienic macro system had been relegated to an appendix of the R4RS standard, as a "high level" system alongside a "low level" macro system, both of which were treated as extensions to Scheme rather than an essential part of the language.[26]

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Alonzo Church's mathematical notation, the lambda calculus, has inspired Lisp's use of "lambda" as a keyword for introducing a procedure, as well as influencing the development of functional programming techniques involving the use of higher-order functions in Lisp. But early Lisps were not suitable expressions of the lambda calculus because of their treatment of free variables.[8]

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R6RS introduces numerous significant changes to the language.[12] The source code is now specified in Unicode, and a large subset of Unicode characters may now appear in Scheme symbols and identifiers, and there are other minor changes to the lexical rules. Character data is also now specified in Unicode. Many standard procedures have been moved to the new standard libraries, which themselves form a large expansion of the standard, containing procedures and syntactic forms that were formerly not part of the standard. A new module system has been introduced, and systems for exception handling are now standardized. Syntax-rules has been replaced with a more expressive syntactic abstraction facility (syntax-case) which allows the use of all of Scheme at macro expansion time. Compliant implementations are now required to support Scheme's full numeric tower, and the semantics of numbers have been expanded, mainly in the direction of support for the IEEE 754 standard for floating point numerical representation.

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See also: agenda, arrangement, artifice, avenue, blueprint, cabal, campaign, circumvent, codification, connivance, connive, conspiracy, conspire, contrivance, contrive, course, design, device, devise, direction, endeavor, enterprise, expedient, forethought, form, formulate, frame, goal, hoax, intend, intent, invent, machination, maneuver, mode, organization, plan, platform, plot, ploy, policy, practice, procedure, process, program, project, proposal, proposition, prospectus, racket, ruse, stratagem, strategy, structure, suggestion, system, trick, undertaking

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See also: agenda, arrangement, artifice, avenue, blueprint, cabal, campaign, circumvent, codification, connivance, connive, conspiracy, conspire, contrivance, contrive, course, design, device, devise, direction, endeavor, enterprise, expedient, forethought, form, formulate, frame, goal, hoax, intend, intent, invent, machination, maneuver, mode, organization, plan, platform, plot, ploy, policy, practice, procedure, process, program, project, proposal, proposition, prospectus, racket, ruse, stratagem, strategy, structure, suggestion, system, trick, undertaking

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Scheme is widely used by a number[37] of schools; in particular, a number of introductory Computer Science courses use Scheme in conjunction with the textbook Structure and Interpretation of Computer Programs (SICP).[38] For the past 12 years, PLT has run the ProgramByDesign (formerly TeachScheme!) project, which has exposed close to 600 high school teachers and thousands of high school students to rudimentary Scheme programming. MIT's old introductory programming class 6.001 was taught in Scheme,[39] Although 6.001 has been replaced by more modern courses, SICP continues to be taught at MIT.[40] The textbook How to Design Programs by Matthias Felleisen, currently at Northeastern University, is used by some institutes of higher education for their introductory computer science courses. Both Northeastern University and Worcester Polytechnic Institute use Scheme exclusively for their introductory courses Fundamentals of Computer Science (CS2500) and Introduction to Program Design (CS1101), respectively.[41][42] Rose-Hulman uses Scheme in its more advanced Programming Language Concepts course.[43] Indiana University's introductory class, C211, is taught entirely in Scheme. The introductory class at UC Berkeley, CS 61A, was until 2015 taught entirely in Scheme, save minor diversions into Logo to demonstrate dynamic scope; all course materials, including lecture webcasts, are available online free of charge.[44] A self-paced version of the course, CS 61AS, continues to use Scheme.[45] The introductory computer science courses at Yale and Grinnell College are also taught in Scheme.[46] Programming Design Paradigms,[47] a mandatory course for the Computer science Graduate Students at Northeastern University, also extensively uses Scheme. The introductory Computer Science course at the University of Minnesota - Twin Cities, CSCI 1901, also uses Scheme as its primary language, followed by a course that introduces students to the Java programming language.[48] In the software industry, Tata Consultancy Services, Asia's largest software consultancy firm, uses Scheme in their month-long training program for fresh college graduates.[citation needed]

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The R5RS standard specifies procedures exact->inexact and inexact->exact which can be used to change the exactness of a number. inexact->exact produces "the exact number that is numerically closest to the argument". exact->inexact produces "the inexact number that is numerically closest to the argument". The R6RS standard omits these procedures from the main report, but specifies them as R5RS compatibility procedures in the standard library (rnrs r5rs (6)).

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