The Basis System - Weapons and Complex Integration - Lawrence ...

if you have trouble tracking down a syntax error, don’t confine your search to the immediate
neighborhood where it was detected. It could have been many lines previous.
10.2.2 Semantic Errors
Many times the Basis diagnostics for semantic errors make it very easy to discover what was
wrong. For example, the statement
b = c + a
produces the following diagnostic (when debug is yes):
parasgn2: Shape mismatch between source and target in
assignment or append.
Right side (source) true dimension= 2 true shape= 10 10
Left side (target) true dimension= 0 true shape=
parasgn: error in assignment to variable named ’b’.
Writing traceback info to file trace24589x
Returned to user input level.
Clearly the problem is that the right side is a 10 by 10 array, and the left side b is a scalar, so this
is an illegal assignment.
Sometimes the traceback information can be useful; if you examine the traceback file (in this case
trace24589x), you will find that it contains
Here is the information I have on where you were:
The error occurred in the assignment or append statement:
b = expression
The following lines contain clues(not facts) about the r. h. s.
c+a
Parser’s action number = 3(ASSIGN ), program counter = 26.
Frequently a semantic error will be detected inside a function, or perhaps nested inside several
function calls. The error printout may concern a variable or parameter local to the function where
execution is taking place, and the name of the variable seems totally off the wall. For instance,
consider the declaration and function call:
integer z ( 2 , 4 , 5 )
call f ( z )
This function call produced the following error diagnostic:
46 Chapter 10. Error Recovery and Diagnosis