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Show ü Hl. The LaMguaaa ^Environment A. Bacplanätion o| the Feramliims Ueafl Syntax Two formalisms are used to describe the syntax of FLEX» A variant of BNF (Backus Normal Form) (with , factoring) and the syntax-chart method developed by Burroughs Corporation. Uoi For an example, let us describe a FLEX identifier. In Englishi An identifier is a text string of arbitrary length starting with a letter and thereafter composed of either letter* of numbers. <ident>ii"<l«tter> |<ident> In BMFi < letter> |<ident><number> In Chart: i '. - fcl-»lletierl nunfcerj - tEroa .A box says that the construct is defined elsewhere on the chart; a lozenge indicates that this is the definition. Semantics and Pragmatics The semantics and pragmatics of FLEX will be largely described in English (drawing heavily from accepted notions in mathematics and computer science). Whenever possible, FLEX, itself, will be used for description and, indeed, this is done in the SCRIBE chapter where FLEX is presented written in itself. |
