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51-561: It also includes most of the uncommon symbols used by the APL programming language. In Unicode , Miscellaneous Technical symbols placed in the hexadecimal range 0x 2300 –0x 23FF , (decimal 8960–9215), as described below. The Miscellaneous Technical block contains eighteen emoji : U+231A–U+231B, U+2328, U+23CF, U+23E9–U+23F3 and U+23F8–U+23FA. All of these characters have standardized variants defined, to specify emoji-style (U+FE0F VS16) or text presentation (U+FE0E VS15) for each character, for

102-485: A derived or composed function (named im at left) is used in the APL user session to return a 9- element identity matrix using its right argument , parameter or operand = 3. Example using APL to index ⍳ or find (or not find) elements in a character vector : First, variable Letters is assigned a vector of 5-elements, in this case - letters of the alphabet. The shape ⍴ or character vector-length of Letters

153-462: A source-code editor that can alert the programmer to common errors. Modification often includes code refactoring (improving the structure without changing functionality) and restructuring (improving structure and functionality at the same time). Nearly every change to code will introduce new bugs or unexpected ripple effects , which require another round of fixes. Code reviews by other developers are often used to scrutinize new code added to

204-430: A trade secret . Proprietary, secret source code and algorithms are widely used for sensitive government applications such as criminal justice , which results in black box behavior with a lack of transparency into the algorithm's methodology. The result is avoidance of public scrutiny of issues such as bias. Access to the source code (not just the object code) is essential to modifying it. Understanding existing code

255-448: A 2-element vector of character strings {"Apples" "Oranges"} could be substituted for numeric vector {45 67} above. In APL the precedence hierarchy for functions or operators is strictly positional: expressions are evaluated right-to-left. APL does not follow the usual operator precedence of other programming languages; for example, × does not bind its operands any more "tightly" than + . Instead of operator precedence, APL defines

306-431: A computer, at base, only understands machine code , source code must be translated before a computer can execute it. The translation process can be implemented three ways. Source code can be converted into machine code by a compiler or an assembler . The resulting executable is machine code ready for the computer. Alternatively, source code can be executed without conversion via an interpreter . An interpreter loads

357-407: A custom function to arrays, but also its use anywhere that a dyadic function may reasonably be used such as in generation of a table of results: Source code In computing , source code , or simply code or source , is a plain text computer program written in a programming language . A programmer writes the human readable source code to control the behavior of a computer . Since

408-505: A dyadic composite function applied to the vectors on its left and right. If the function to the left of the dot is "∘" (signifying null) then the composite function is an outer product, otherwise it is an inner product. An inner product intended for conventional matrix multiplication uses the + and × functions, replacing these with other dyadic functions can result in useful alternative operations. Some functions can be followed by an axis indicator in (square) brackets, i.e., this appears between

459-408: A few numbers together. (From a vector, ×/ returns the product of all its elements.) The above dyadic functions examples [left and right examples] (using the same / symbol, right example) demonstrate how Boolean values (0s and 1s) can be used as left arguments for the \ expand and / replicate functions to produce exactly opposite results. On the left side, the 2-element vector {45 67}

510-401: A function CURVEAREA could be defined twice to replace both monadic CIRCLEAREA and dyadic SEGMENTAREA above, with the monadic or dyadic function being selected by the context in which it was referenced. Custom dyadic functions may usually be applied to parameters with the same conventions as built-in functions, i.e., arrays should either have the same number of elements or one of them should have

561-402: A function and an array and should not be confused with array subscripts written after an array. For example, given the ⌽ (reversal) function and a two-dimensional array, the function by default operates along the last axis but this can be changed using an axis indicator: 4 rows by 3 cols matrix created, using rho ⍴ and iota ⍳ . The 4 x 3 matrix is then stored in a variable named A . A

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612-441: A non-textual symbol. The function header defines whether a custom function is niladic (no arguments), monadic (one right argument) or dyadic (left and right arguments), the local name of the result (to the left of the ← assign arrow), and whether it has any local variables (each separated by semicolon ';'). Whether functions with the same identifier but different adicity are distinct is implementation-defined. If allowed, then

663-521: A notion of scope . The scope of a function determines its arguments . Functions have long right scope : that is, they take as right arguments everything to their right. A dyadic function has short left scope : it takes as its left arguments the first piece of data to its left. For example, (leftmost column below is actual program code from an APL user session , indented = actual user input , not-indented = result returned by APL interpreter ): << First note there are no parentheses and APL

714-444: A project. The purpose of this phase is often to verify that the code meets style and maintainability standards and that it is a correct implementation of the software design . According to some estimates, code review dramatically reduce the number of bugs persisting after software testing is complete. Along with software testing that works by executing the code, static program analysis uses automated tools to detect problems with

765-426: A single element which is extended. There are exceptions to this, for example a function to convert pre-decimal UK currency to dollars would expect to take a parameter with precisely three elements representing pounds, shillings and pence. Inside a program or a custom function, control may be conditionally transferred to a statement identified by a line number or explicit label; if the target is 0 (zero) this terminates

816-406: A specific platform, source code can be ported to a different machine and recompiled there. For the same source code, object code can vary significantly—not only based on the machine for which it is compiled, but also based on performance optimization from the compiler. Most programs do not contain all the resources needed to run them and rely on external libraries . Part of the compiler's function

867-620: A total of 36 variants. The following Unicode-related documents record the purpose and process of defining specific characters in the Miscellaneous Technical block: APL syntax and symbols The programming language APL is distinctive in being symbolic rather than lexical : its primitives are denoted by symbols , not words. These symbols were originally devised as a mathematical notation to describe algorithms. APL programmers often assign informal names when discussing functions and operators (for example, "product" for ×/) but

918-406: Is expanded where Boolean 0s occur to result in a 3-element vector {45 0 67} — note how APL inserted a 0 into the vector. Conversely, the exact opposite occurs on the right side — where a 3-element vector becomes just 2-elements; Boolean 0s delete items using the dyadic / slash function. APL symbols also operate on lists (vector) of items using data types other than just numeric, for example

969-537: Is greater than 1 ) is a 4 row by 2 column matrix. Arrays are structures which have elements grouped linearly as vectors or in table form as matrices —and higher dimensions (3D or cubed, 4D or cubed over time , etc.). Arrays containing both characters and numbers are termed mixed arrays . Array structures containing elements which are also arrays are called nested arrays . X set = to matrix with 4 rows by 5 columns, consisting of 20 consecutive integers. Element X[2;2] in row 2 - column 2 currently

1020-646: Is 5. Variable FindIt is assigned what to search for in Letters and its length is 4 characters. 1 2 3 4 5 << vector positions or index #'s in Letters ABCDE At left, dyadic function iota searches through its left argument(Letters) for the search string (iota's right argument, FindIt). Iota finds letter "C" at position 3 in Letters, it finds "A" at position 1, and "B" at position 2. Iota does not find letter "S" anywhere in variable Letters so it returns

1071-510: Is an integer = 7 . Initial index origin ⎕IO value = 1 . Thus, the first element in matrix X or X[1;1] = 1 . Element in X[row 3; col 4], formerly integer 14, now becomes a mini enclosed or ⊂ nested 2x2 matrix of 4 consecutive integers. Since X contains numbers , text and nested elements , it is both a mixed and a nested array. A user may define custom functions which, like variables, are identified by name rather than by

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1122-442: Is an overarching term that can refer to a code's correct and efficient behavior, its reusability and portability , or the ease of modification. It is usually more cost-effective to build quality into the product from the beginning rather than try to add it later in the development process. Higher quality code will reduce lifetime cost to both suppliers and customers as it is more reliable and easier to maintain . Maintainability

1173-452: Is frequently cited as a contributing factor to the maturation of their programming skills. Some people consider source code an expressive artistic medium . Source code often contains comments —blocks of text marked for the compiler to ignore. This content is not part of the program logic, but is instead intended to help readers understand the program. Companies often keep the source code confidential in order to hide algorithms considered

1224-412: Is going to execute from right-to-left. Step 1{of topmost APL code entered at left}) 4-5 = -1. Step 2) 3 times -1 = -3. Step 3) Take the floor or lower of 2 and -3 = -3. Step 4) Divide 1 by -3 = -0.3333333333 = final result. An operator may have function or data operands and evaluate to a dyadic or monadic function. Operators have long left scope. An operator takes as its left operand

1275-496: Is necessary to understand how it works and before modifying it. The rate of understanding depends both on the code base as well as the skill of the programmer. Experienced programmers have an easier time understanding what the code does at a high level. Software visualization is sometimes used to speed up this process. Many software programmers use an integrated development environment (IDE) to improve their productivity. IDEs typically have several features built in, including

1326-466: Is now reflected or flipped along its vertical axis as symbol ⌽ visually indicates. A is now reflected using the [1] axis indicator or first dimension modifier . The result is that variable A has been reflected across the horizontal axis, instead of vertically. A is now reflected both vertically ⊖ and horizontally ⌽ . A is ⍉ transposed to a 3 row by 4 col matrix such that rows-cols become exchanged, as symbol ⍉ visually portrays. Compare

1377-617: Is that many software engineering courses do not emphasize it. Development engineers who know that they will not be responsible for maintaining the software do not have an incentive to build in maintainability. The situation varies worldwide, but in the United States before 1974, software and its source code was not copyrightable and therefore always public domain software . In 1974, the US Commission on New Technological Uses of Copyrighted Works (CONTU) decided that "computer programs, to

1428-477: Is the quality of software enabling it to be easily modified without breaking existing functionality. Following coding conventions such as using clear function and variable names that correspond to their purpose makes maintenance easier. Use of conditional loop statements only if the code could execute more than once, and eliminating code that will never execute can also increase understandability. Many software development organizations neglect maintainability during

1479-418: Is to link these files in such a way that the program can be executed by the hardware. Software developers often use configuration management to track changes to source code files ( version control ). The configuration management system also keeps track of which object code file corresponds to which version of the source code file. The number of lines of source code is often used as a metric when evaluating

1530-443: The compose operator ∘ and the commute operator ⍨ . The former ∘ glues functions together so that foo∘bar , for example, could be a hypothetical function that applies defined function foo to the result of defined function bar ; foo and bar can represent any existing function. In cases where a dyadic function is moderated by commute and then used monadically, its right argument is taken as its left argument as well. Thus,

1581-458: The compilers needed to translate the source code automatically into machine code that can be directly executed on the computer hardware . Source code is the form of code that is modified directly by humans, typically in a high-level programming language. Object code can be directly executed by the machine and is generated automatically from the source code, often via an intermediate step, assembly language . While object code will only work on

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1632-622: The outer product of the equals function. The result of ∘.=/ is a monadic function. With a function's usual long right scope, it takes as its right argument the result of ⍳¨3 3. Thus Equivalent results in APL: (⍳3)(⍳3) and ⍳¨3 3 << Rightmost expression is more concise . The matrix of 1s and 0s similarly produced by ∘.=/⍳¨3 3 and (⍳3)∘.=⍳3 is called an identity matrix . Identity matrices are useful in solving matrix determinants , groups of linear equations and multiple regression . Some APL interpreters support

1683-422: The APL interpreter reads 3 3 over each use iota), concisely: iota for each 3 . The left operand for the over-each operator ¨ is the index ⍳ function. The derived function ⍳¨ is used monadically and takes as its right operand the vector 3 3 . The left scope of each is terminated by the reduce operator, denoted by the forward slash . Its left operand is the function expression to its left:

1734-402: The axis indicator is less than or greater than the index origin (index origin = 1 in illustration below): At left, variable 'B' is first assigned a vector of 4 consecutive integers (e.g., ⍳4 ). Var C is then assigned 4 more consecutive integers (such as 4+⍳4 ). 'B' and C are then concatenated or raveled together for illustration purposes, resulting in a single vector ( ⍳8 ). In

1785-471: The core functions and operators provided by the language are denoted by non-textual symbols. Most symbols denote functions or operators . A monadic function takes as its argument the result of evaluating everything to its right. (Moderated in the usual way by parentheses.) A dyadic function has another argument, the first item of data on its left. Many symbols denote both monadic and dyadic functions, interpreted according to use. For example, ⌊3.2 gives 3,

1836-400: The details of the hardware, instead being designed to express algorithms that could be understood more easily by humans. As instructions distinct from the underlying computer hardware , software is therefore relatively recent, dating to these early high-level programming languages such as Fortran , Lisp , and Cobol . The invention of high-level programming languages was simultaneous with

1887-426: The development phase, even though it will increase long-term costs. Technical debt is incurred when programmers, often out of laziness or urgency to meet a deadline, choose quick and dirty solutions rather than build maintainability into their code. A common cause is underestimates in software development effort estimation , leading to insufficient resources allocated to development. A challenge with maintainability

1938-406: The extent that they embody an author's original creation, are proper subject matter of copyright". Proprietary software is rarely distributed as source code. Although the term open-source software literally refers to public access to the source code , open-source software has additional requirements: free redistribution, permission to modify the source code and release derivative works under

1989-475: The instructions can be carried out. After being compiled, the program can be saved as an object file and the loader (part of the operating system) can take this saved file and execute it as a process on the computer hardware. Some programming languages use an interpreter instead of a compiler. An interpreter converts the program into machine code at run time , which makes them 10 to 100 times slower than compiled programming languages. Software quality

2040-634: The largest integer not above the argument, and 3⌊2 gives 2, the lower of the two arguments. APL uses the term operator in Heaviside ’s sense as a moderator of a function as opposed to some other programming language's use of the same term as something that operates on data, ref. relational operator and operators generally . Other programming languages also sometimes use this term interchangeably with function , however both terms are used in APL more precisely. Early definitions of APL symbols were very specific about how symbols were categorized. For example,

2091-439: The longest function to its left. For example: APL atomic or piecemeal sub-analysis ( full explanation ): Beginning rightmost: ⍳¨3 3 produces a 2-element nested APL vector { {1 2 3} {1 2 3} } where each element is itself a vector {1 2 3}. Iota ⍳3 by itself would produce {1 2 3}. The diaeresis ¨ or mini double-dot means repeat or over each or perform each separately so iota repeats (in human i.e., reversed terms,

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2142-450: The number 6 which is 1 greater than the length of Letters. Iota found letters "CAB" (3 1 2). Iota correctly did not find "S" (6). Negatives produce the inverse of the respective functions Notes: The reduce and scan operators expect a dyadic function on their left, forming a monadic composite function applied to the vector on its right. The product operator "." expects a dyadic function on both its left and right, forming

2193-459: The operator reduce is denoted by a forward slash and reduces an array along one axis by interposing its function operand . An example of reduce : In the above case, the reduce or slash operator moderates the multiply function. The expression ×/2 3 4 evaluates to a scalar (1 element only) result through reducing an array by multiplication. The above case is simplified, imagine multiplying (adding, subtracting or dividing) more than just

2244-794: The parameters (DEGREES and RADIUS below) are of different sign: The above function SEGMENTAREA works as expected if the parameters are scalars or single-element arrays , but not if they are multiple-element arrays since the condition ends up being based on a single element of the SIGN array - on the other hand, the user function could be modified to correctly handle vectorized arguments. Operation can sometimes be unpredictable since APL defines that computers with vector-processing capabilities should parallelise and may reorder array operations as far as possible - thus, test and debug user functions particularly if they will be used with vector or even matrix arguments. This affects not only explicit application of

2295-450: The particular case at left, if the dyadic catenate "," function is followed by an axis indicator ( [0.5] which is less than 1 ), it can be used to laminate ( interpose ) two arrays (vectors in this case) depending on whether the axis indicator is less than or greater than the index origin(1). The first result (of B,[0.5]C ) is a 2 row by 4 column matrix, vertically joining 'B' and C row-wise. The second result (of B,[1.5]C which

2346-426: The processor). Machine language was difficult to debug and was not portable between different computer systems. Initially, hardware resources were scarce and expensive, while human resources were cheaper. As programs grew more complex, programmer productivity became a bottleneck. This led to the introduction of high-level programming languages such as Fortran in the mid-1950s. These languages abstracted away

2397-465: The productivity of computer programmers, the economic value of a code base, effort estimation for projects in development, and the ongoing cost of software maintenance after release. Source code is also used to communicate algorithms between people – e.g., code snippets online or in books. Computer programmers may find it helpful to review existing source code to learn about programming techniques. The sharing of source code between developers

2448-434: The program or returns to a function's caller. The most common form uses the APL compression function, as in the template (condition)/target which has the effect of evaluating the condition to 0 (false) or 1 (true) and then using that to mask the target (if the condition is false it is ignored, if true it is left alone so control is transferred). Hence function SEGMENTAREA may be modified to abort (just below), returning zero if

2499-420: The result here to the original matrix stored in A, topmost matrix. These types of data transformations are useful in time series analysis and spatial coordinates , just two examples, more exist . As a particular case, if the dyadic catenate "," function is followed by an axis indicator (or axis modifier to a symbol/function), it can be used to laminate (interpose) two arrays depending on whether

2550-432: The source code into memory. It simultaneously translates and executes each statement . A method that combines compilation and interpretation is to first produce bytecode . Bytecode is an intermediate representation of source code that is quickly interpreted. The first programmable computers, which appeared at the end of the 1940s, were programmed in machine language (simple instructions that could be directly executed by

2601-414: The source code. Many IDEs support code analysis tools, which might provide metrics on the clarity and maintainability of the code. Debuggers are tools that often enable programmers to step through execution while keeping track of which source code corresponds to each change of state. Source code files in a high-level programming language must go through a stage of preprocessing into machine code before

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