.sp 2
.NH
Deviations from the standard
.nh

.PP
The compiler deviates from the ISO 7185 standard with respect to the
following clauses:

.IP "\fBISO 6.1.3:\fR" 14
\h'-5u'Identifiers may be of any length and all characters of an identifier
shall be significant in distinguishing between them.
.sp
.in +3m
The constant IDFSIZE, defined in the file \fIidfsize.h\fR, determines
the (maximum) significant length of an identifier. It can be set at run
time with the \-M option (see also section on compiler options).
.in -3m
.sp
.IP "\fBISO 6.1.8:\fR"
\h'-5u'There shall be at least one separator between any pair of consecutive tokens
made up of identifiers, word-symbols, labels or unsigned-numbers.
.sp
.in +3m
A token separator is not needed when a number is followed by an identifier
or a word-symbol. For example the input sequence, 2\fBthen\fR, is recognized
as the integer 2 followed by the keyword \fBthen\fR.
.in -3m
.sp
.IP "\fBISO 6.2.1:\fR"
\h'-29u'The label-declaration-part shall specify all labels that prefix a statement
in the corresponding statement-part.
.sp
.ti +3m
The compiler generates a warning if a label is declared but never defined.
.bp
.IP "\fBISO 6.2.2:\fR"
\h'-9u'The scope of identifiers and labels should start at the beginning of the
block in which these identifiers or labels are declared.
.sp
.in +3m
The compiler, as most other one pass compilers deviates in this respect,
because the scope of variables and labels start at their defining-point.
.nf
.in +4m
\fBprogram\fR deviates\fB;
const\fR
        x \fB=\fR 3\fB;
procedure\fR p\fB;
const\fR
	y \fB=\fR x\fB;\fR
	x \fB=\fR true\fB;
begin end;
begin
end.\fR
.in -4m
.fi

In procedure p, the constant y has the integer value 3. This program does not
conform to the standard. In [SAL] a simple algorithm is described for
enforcing the scope rules, it involves numbering all scopes encoutered in the
program in order of their opening, and recording in each identifier table
entry the number of the latest scope in which it is used.

Note: The compiler does not deviate from the standard in the following program:
.nf
.in +4m
\fBprogram\fR conforms\fB;
type\fR
	x \fB=\fR real\fB;
procedure\fR p\fB;
type\fR
	y \fB= ^\fRx\fB;\fR
	x \fB=\fR boolean\fB;
var\fR
	p \fB:\fR y\fB;
begin end;
begin
end.\fR
.in -4m
.fi

In procedure p, the variable p is a pointer to boolean.
.fi
.in -3m
.sp
.IP "\fBISO 6.4.3.2:\fR"
The standard specifies that any ordinal type is allowed as index-type.
.sp
.in +3m
The required type \fIinteger\fR is not allowed as index-type, i.e.
.ti +2m
\fBARRAY [ \fIinteger\fB ] OF\fR <component-type>
is not permitted.
.br
This could be implemented, but this might cause problems on machines with
a small memory.
.in -3m
.sp
.IP "\fBISO 6.4.3.3:\fR"
\h'-1u'The type possessed by the variant-selector, called the tag-type, must
be an ordinal type, so the integer type is permitted. The values denoted by
all case-constants shall be distinct and the set thereof shall be equal
to the set of values specified by the tag-type.
.sp
.in +3m
Because it is impracticable to enumerate all integers as case-constants,
the integer type is not permitted as tag-type. It would not make a great
difference to allow it as tagtype.
.in -3m
.sp
.IP "\fBISO 6.8.3.9:\fR"
The standard specifies that the control-variable of a for-statement is not
allowed to be modified while executing the loop.
.sp
.in +3m
Violation of this rule is not detected. An algorithm to implement this rule
can be found in [PCV].