HP SunSoft Pascal 4.0 Manual de usuario descargar pdf (Pagina 231)

Error Diagnostics 207

Replacements, Insertions, and Deletions

When Pascal encounters a syntax error in the input text, the compiler invokes

an error recovery procedure. This procedure examines the input text

immediately after the point of error and uses a set of simple corrections to

determine whether or not to allow the analysis to continue. These corrections

involve replacing an input token with a different token or inserting a token.

Most of these changes do not cause fatal syntax errors.

The exception is the insertion of or replacement with a symbol, such as an

identiﬁer or a number; in these cases, the recovery makes no attempt to

determine which identiﬁer or what number should be inserted. Thus, these are

considered fatal syntax errors.

The Pascal program,

synerr.p, which uses ** as an

exponentiation operator

program synerr_example(output);

var i, j are integer;

begin

for j :* 1 to 20 begin

write(j);

i = 2 ** j;

writeln(i))

end

end. { synerr_example }

synerr.p produces a fatal

syntax error when you compile it

because Pascal does not have

an exponentiation operator.

hostname% pc synerr.p

Mon Feb 13 10:56:19 1995 synerr.p:

3 var i, j are integer;

e 18460----------------^--- Replaced identifier with a ':'

6 for j :* 1 to 20 begin

E 18490-----------------^--- Expected keyword (null)

E 18460-----------------^--- Replaced ':' with a identifier

e 18480----------------------------^--- Inserted keyword do

8 i = 2 ** j;

e 18480---------------^--- Inserted keyword if

E 18480----------------------^--- Inserted identifier

e 18480-------------------------^--- Inserted keyword then

9 writeln(i))

e 18450-------------------------^--- Deleted ')'

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HP SunSoft Pascal 4.0 Manual de usuario Pagina 231