Robert.Firth@SEI.CMU.EDU (09/22/87)
The problems with "1:=" generating an error can be traced to [RM 2.4.2 - Based Literals] and [RM 2.10 - Allowable Replacements of Characters]. The compiler believes that the sequence "1:" introduces a based literal, for instance "1:0123:". Accordingly, it fails on the "=" character, which cannot be part of a based literal. Recall that, while based literals are usually written "2#1010#", the colon is an allowable replacement for the hachure. You should expect various error messages, such as "illegal char in based literal", "invalid base in based literal", and so on. This lexis is correct according to the RM - indeed, any alternative would no longer be LR(1) and so would cause trouble for automatic scanner generators. And the colon is a replacement character because Steelman required that Ada be representable using a 56-character set. Sigh.