Perbandingan -- programming languages (basic instructions)

Perbandingan -- programming languages is a common topic of discussion among software engineers. Basic instructions of several programming languages are compared here.

Conventions of this article

The bold is the literal code. The non-bold is interpreted by the reader. Statements in guillemets (« … ») are optional. Tab ↹ indicates a necessary indent.

Type identifiers

Integers

^a The standard constants int shorts and int lengths can be used to determine how many shorts and longs can be usefully prefixed to short int and long int. The actually size of the short int, int and long int is available as constants short max int, max int and long max int etc.
^b Commonly used for characters.
^c The ALGOL 68, C and C++ languages do not specify the exact width of the integer types "short", "int", "long", and (C99, C++11) "long long", so they are implementation-dependent. In C and C++ "short", "long", and "long long" types are required to be at least 16, 32, and 64 bits wide, respectively, but can be more. The "int" type is required to be at least as wide as "short" and at most as wide as "long", and is typically the width of the word size on the processor of the machine (i.e. on a 32-bit machine it is often 32 bits wide; on 64-bit machines it is often 64 bits wide). C99 and C++11^{[citation needed]} also define the "[u]intN_t" exact-width types in the stdint.h header. See C syntax#Integral types for more information.
^d Perl 5 does not have distinct types. Integers, floating point numbers, strings, etc. are all considered "scalars".
^e PHP has two arbitrary-precision libraries. The BCMath library just uses strings as datatype. The GMP library uses an internal "resource" type.
^f The value of "n" is provided by the SELECTED_INT_KIND^[3] intrinsic function.
^g ALGOL 68G's run time option --precision "number" can set precision for long long int's to the required "number" significant digits. The standard constants long long int width and long long max int can be used to determine actual precision.
^h COBOL allows the specification of a required precision and will automatically select an available type capable of representing the specified precision. "PIC S9999", for example, would required a signed variable of four decimal digits precision. If specified as a binary field, this would select a 16 bit signed type on most platforms.
^i Smalltalk automatically chooses an appropriate representation for integral numbers. Typically, two representations are present, one for integers fitting the native word size minus any tag bit (SmallInteger) and one supporting arbitrary sized integers (LargeInteger). Arithmetic operations support polymorphic arguments and return the result in the most appropriate compact representation.

Floating point

^a The standard constants real shorts and real lengths can be used to determine how many shorts and longs can be usefully prefixed to short real and long real. The actually size of the short real, real and long real is available as constants short max real, max real and long max real etc. With the constants short small real, small real and long small real available for each type's machine epsilon.
^b declarations of single precision often are not honored
^c The value of "n" is provided by the SELECTED_REAL_KIND^[5] intrinsic function.
^d ALGOL 68G's run time option --precision "number" can set precision for long long real's to the required "number" significant digits. The standard constants long long real width and long long max real can be used to determine actual precision.
^e COBOL also supports FLOAT-EXTENDED. The types FLOAT-BINARY-7, FLOAT-BINARY-16 and FLOAT-BINARY-34, specify IEEE-754 binary floating point variables, and FLOAT-DECIMAL-16 and FLOAT-DECIMAL-34 specify IEEE decimal floating point variables.

Complex numbers

^a The value of "n" is provided by the SELECTED_REAL_KIND^[5] intrinsic function.

Other variable types

^a specifically, strings of arbitrary length and automatically managed.
^b This language represents a boolean as an integer where false is represented as a value of zero and true by a non-zero value.
^c All values evaluate to either true or false. Everything in TrueClass evaluates to true and everything in FalseClass evaluates to false.
^d This language does not have a separate character type. Characters are represented as strings of length 1.
^e Enumerations in this language are algebraic types with only nullary constructors
^f The value of "n" is provided by the SELECTED_INT_KIND^[3] intrinsic function.

Derived types

Array

^a In most expressions (except the sizeof and & operators), values of array types in C are automatically converted to a pointer of its first argument. Also C's arrays can not be described in this format. See C syntax#Arrays.
^b The C-like "type x[]" works in Java, however "type[] x" is the preferred form of array declaration.
^c Subranges are used to define the bounds of the array.
^d JavaScript's array are a special kind of object.

Other types

^a Only classes are supported.
^b structs in C++ are actually classes, but have default public visibility and are also POD objects. 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.
^e Enumerations in this language are algebraic types with only nullary constructors

Variable and constant declarations

^a Pascal has declaration blocks. See Perbandingan -- programming languages (basic instructions)#Functions.
^b Types are just regular objects, so you can just assign them.
^c In Perl, the "my" keyword scopes the variable into the block.
^d Technically, this does not declare name to be a mutable variable—in ML, all names can only be bound once; rather, it declares name to point to a "reference" data structure, which is a simple mutable cell. The data structure can then be read and written to using the ! and := operators, respectively.

Control flow

Conditional statements

^a A single instruction can be written on the same line following the colon. Multiple instructions are grouped together in a block which starts on a newline (The indentation in required). The conditional expression syntax does not follow this rule.
^b This is pattern matching and is similar to select case but not the same. It is usually used to deconstruct algebraic data types.
^c In languages of the Pascal family, the semicolon is not part of the statement. It is a separator between statements, not a terminator.

Loop statements

^a "step n" is used to change the loop interval. If "step" is omitted, then the loop interval is 1.

Exceptions

^a Common Lisp allows with-simple-restart, restart-case and restart-bind to define restarts for use with invoke-restart. Unhandled conditions may cause the implementation to show a restarts menu to the user before unwinding the stack.

Other control flow statements

^a Pascal has declaration blocks. See Perbandingan -- programming languages (basic instructions)#Functions.
^b label must be a number between 1 and 99999.

Functions

See reflection for calling and declaring functions by strings.

^a Pascal requires "forward;" for forward declarations.
^b Eiffel allows the specification of an application's root class and feature.
^c In Fortran, function/subroutine parameters are called arguments (since PARAMETER is a language keyword); the CALL keyword is required for subroutines.

^[c]

Type conversions

Where string is a signed decimal number:

^a JavaScript only uses floating point numbers so there are some technicalities.^[4]
^b Perl doesn't have separate types. Strings and numbers are interchangeable.

Standard stream I/O

^a Algol 68 additionally as the "unformatted" transput routines: read, write, get and put.
^b gets(x) and fgets(x, length, stdin) read unformatted text from stdin. Use of gets is not recommended.
^c puts(x) and fputs(x, stdout) write unformatted text to stdout.
^d fputs(x, stderr) writes unformatted text to stderr
^e INPUT_UNIT, OUTPUT_UNIT, ERROR_UNIT are defined in the ISO_FORTRAN_ENV module.^[7]

Reading command-line arguments

• ^a The command-line arguments in Visual Basic are not separated. A split function Split(string) is required for separating them.

Execution of commands

^a Compiler-dependent extension.^[8]

References