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For example, consider variables a, b and c of some user-defined type, such as matrices: a + b * c In a language that supports operator overloading, and with the usual assumption that the * operator has higher precedence than the + operator, this is a concise way of writing:
Functions of a single variable (such as sine and cosine) may be implemented by a simple array. Functions involving two or more variables require multidimensional array indexing techniques. The latter case may thus employ a two-dimensional array of power[x][y] to replace a function to calculate x y for a limited range of x and y values ...
Not all variables are in use (or "live") at the same time, so, over the lifetime of a program, a given register may be used to hold different variables. However, two variables in use at the same time cannot be assigned to the same register without corrupting one of the variables. If there are not enough registers to hold all the variables, some ...
The choice of a variable name should be mnemonic — that is, designed to indicate to the casual observer the intent of its use. One-character variable names should be avoided except for temporary "throwaway" variables. Common names for temporary variables are i, j, k, m, and n for integers; c, d, and e for characters. int i;
The data type of variables can be specified with a character at the end of the variable name: A$ is a string of characters, A% is an integer, etc. Groups of variables can also be set to default types based on the initial letter of their name by use of the DEFINT, DEFSTR, etc., statements.
It is easier to alter the value of the number, as it is not duplicated. Changing the value of a magic number is error-prone, because the same value is often used several times in different places within a program. [6] Also, when two semantically distinct variables or numbers have the same value they may be accidentally both edited together. [6]
The phrase grammar of most programming languages can be specified using a Type-2 grammar, i.e., they are context-free grammars, [8] though the overall syntax is context-sensitive (due to variable declarations and nested scopes), hence Type-1. However, there are exceptions, and for some languages the phrase grammar is Type-0 (Turing-complete).
C++11 extended this further, to make classes act identically to POD objects in many more cases. ^c pair only ^d Although Perl doesn't have records, because Perl's type system allows different data types to be in an array, "hashes" (associative arrays) that don't have a variable index would effectively be the same as records.