Comments on the syntax for Miranda scripts The syntax equations given express the syntax of Miranda scripts insofar as this can be done by a context free grammar. It therefore does not attempt to express the scope rules, nor the requirement that a script be well-typed, both of which are context sensitive restrictions on the syntax given here. The formal definition of Miranda [in preparation] will deal with these matters and also give a denotational semantics for the language. Nevertheless, if the syntax is read in conjunction with the informal description of the language (see other manual sections and referenced papers) it should be found fairly informative, especially if the reader has some previous exposure to this style of language. Key to abbreviations in syntax:- > alt=alternative decl=declaration def=definition > e1=operator_expression exp=expression fnform=function_form > libdir=library_directive pat=pattern qualifs=qualifiers > rhs=right_hand_side sig=signature spec=specification > tdef=type_definition tform=typeform var=variable > whdefs=where_defs Conventions We use a variant of BNF, in which non-terminals are represented by lower case words, `:=' is used as the production symbol, and alternative productions are written on successive lines. (These departures from convention are adopted because `::=' and `|' are concrete symbols of the language.) For any non-terminal x, x* means zero or more occurrences of x x? means the presence of x is optional x-list means one or more x's (separated by commas if >1) x(;) means that x is followed by an optional semicolon and is subject to the offside rule (see section on Layout), so that every token of x must lie below or to the right of the first. Provided the layout makes it clear where x terminates, the trailing semicolon may be omitted. Notes The syntax of the library directives (denoted by the non-terminal `libdir') is given in a separate manual entry. Ambiguities in the syntax for `type' and `construct' are resolved by noting that `->' is less binding than `$typename' or `$constructor' and that all three are right associative. In connection with the productions for argtype, note that type such as `[num,bool]' is an abbreviation for `[(num,bool)]' and represents the type of a list of tuples - the Miranda system itself never uses this abbreviation when printing a type, but accepts it in user scripts. (Use of this abbreviation is not recommended - it will probably be removed from the syntax at the next release.) Ambiguities in the syntax for `fnform' and `pat' are resolved by taking into account the relative binding powers of the infix operators involved. Specifically that `:' is right associative and less binding than `+', which is left associative, and that $constructor, $var have a higher binding power than either of these, and are right associative. The productions given for `cases' correctly describe the concrete syntax of these entities, including the way the offside rule is applied to them. This concrete syntax is in one sense misleading, however. Namely in that if a `lastcase' with a trailing `wheredefs' is preceded by a series of alternatives, the scope of the names introduced by the where IS THE WHOLE `cases' IN WHICH IT OCCURS, AND NOT JUST THE `lastcase'. Note that for compatibility with earlier versions of Miranda the use of the keyword `if' is optional. The ambiguities in the syntax given for `e1' are resolved by taking into account the relative binding powers of the operators (see manual section on Operators). The syntax of identifier, IDENTIFIER, literal, literal1, numeral, nat, infix, infix1, prefix, prefix1, and typevar are given under Lexical Syntax (see next manual section).