Miranda lexical syntax

In this section square brackets are used to enclose a set of literal characters, using lex-style conventions, so eg [a-z] means a lower case letter. As usual * and ? are used to mean zero-or-more, and zero-or-one, occurrences of the preceding entity. Parentheses are used for grouping, and subtraction of one syntactic entity from another means set difference. We also revert to using | for alternatives, as in standard BNF.

    script:= (token | layout)*

    layout:= nl | tab | formfeed | space | comment

    comment:= vertical_bar vertical_bar (any - nl)* nl

    token:= identifier | IDENTIFIER | literal | typevar | delimiter

    identifier:= ([a-z] [a-zA-Z0-9_']* ) -  delimiter

    IDENTIFIER:= [A-Z] [a-zA-Z0-9_']*

    literal:= numeral | charconst | stringconst

    literal1:= literal - float

    numeral:= nat | float

    nat:= [0-9] [0-9]*

    float:=  [0-9]* [.] nat epart? | nat epart

    epart:= [e] [+|-]? nat

    charconst:= ['] (visible-[\]|escape) [']

    stringconst:= ["] (visible-[\"]|escape)* ["]

    escape:= [\] ([ntfrb\'"]|nl|ascii_code)

    typevar:= [*][*]*

    delimiter:= - | prefix1 | infix1 | other

    infix1:= ++ | -- | : | \/ | & | > | >= | = | ~= | <= | < | + | * |
            / | div | mod | ^ | . | ! | $identifier | $IDENTIFIER

    infix:= infix1 | -

    prefix1:= ~ | #

    prefix:= prefix1 | -

    other:= abstype | if | otherwise | readvals | show | type | where |
            with | %export | %free | %include | %insert | %list | %nolist |
            = | == | ::= | :: | => | vertical_bar | // | -> | ; | , | ( |
            ) | [ | ] | { | } | <- | .. | $$ | $- | $+ | $*

    vertical_bar:= |

Notes

visible means any non-control character, including space (but not including eg newline), nl means literal newline, and ascii_code is a nat in the range 0..255 (maximum length 3 digits).

Notice that the syntax of numeral does not include negative numbers. Negative constants, such as -3 or -5.05e-17 are parsed by Miranda as applications of the prefix operator - to a positive numeral. This has no semantic significance.

Omission - the definition of layout does not include the additional comment rules for LITERATE SCRIPTS (see separate manual section).