Identifiers

An identifier consists of a letter followed by zero or more additional characters which may be letters digits or occurrences of _ or ' (underscore and single quote) Examples:

    x  yellow  p11d  y'  GROSS_INCOME

Note that both upper and lower case letters are allowed, and they are treated as different, so x and X are not the same identifier. There is no restriction on the length of identifiers, and all the characters are significant in deciding whether two identifiers are the same. Identifiers fall into two different classes (called in the formal syntax identifier' andIDENTIFIER`) depending on whether their initial letter is upper or lower case.

Identifiers are used for three different purposes in Miranda - (i) as variables, i.e. names for values (note that the names of functions are also considered to be variables), (ii) as typenames, such as bool and char, and (iii) as constructors (see section on algebraic types). The names of constructors must begin with an upper case letter, while variables and typenames must begin with a lower case letter.

Reserved words

The following are special symbols of the Miranda language.

abstype div if mod otherwise readvals show type where with

These are often shown as underlined (or bold) in published documents, but in programs they are typed as ordinary lower case words (which means that these words cannot be used as identifiers).

Predefined identifiers

The following identifiers are normally predefined, and thus always in scope. They constitute the standard environment. They are defined in the script "stdenv.m", contained in the directory /usr/lib/miralib.

(a) predefined typenames bool char num sys_message

(b) predefined constructors False True :: bool Appendfile Closefile Exit Stderr Stdout System Tofile :: sys_message

(c) predefined variables abs and arctan cjustify code concat const converse cos decode digit drop dropwhile e entier error exp filemode filter foldl foldl1 foldr foldr1 force fst getenv hd hugenum id index init integer iterate last lay layn letter limit lines ljustify log log10 map map2 max max2 member merge min min2 mkset neg numval or pi postfix product read rep repeat reverse rjustify scan seq showfloat shownum showscaled sin snd sort spaces sqrt subtract sum system take takewhile tinynum tl transpose undef until zip2 zip3 zip4 zip5 zip6 zip (88)

See manual entry Standard environment for more detailed information.

[NB There ought to be a way of suppressing or modifying the inclusion of the standard environment, in case you want to use one of these identifiers for another purpose - a mechanism for doing this will be provided in later releases.]