COMPILER TECHNIQUES FOR MATLAB PROGRAMS ... - CiteSeerX

[nr,nc] = size(x)
avg = sum(x) / nc
(a)
function avg = mean(x)
[nr,nc] = size(x)
avg = sum(x) / nc
(b)
Figure 3.2: M-le to compute the mean of a vector using (a) script and (b) function.
accept parameters and operates on the scope of the caller. Figure 3.2 (a) shows a script le
to compute the mean of vector x. Notice that the variable avg is updated with the mean of
x, that is a variable in the scope of the program of function that called the script.
A function diers from a script in that arguments may be passed, and that variables
dened and manipulated inside the le are local to the function and do not operate on
the workspace of its caller.
Figure 3.2 (b) shows a function to compute the mean of a
vector. Notice that in this example, the body of the function is the same as the script le
however, the function's input variable is given as an argument, and the output is dened
in the function denition. One important characteristic of M-le functions in MATLAB is
that they are side-eect free. This functionality can be used to facilitate the exploitation of
functional parallelism [GP92] and loop parallelism.
To avoid confusion, from here on when the term function is used alone in the text, it will
refer to M-le functions and built-in functions only, and not to script les. Similarly, the
term M-le will refer to M-le functions and not to script les.
3.2.2 Scanner, Parser, and the Symbol Table Generation
Initially, aLALR(1) grammar [ASU85] was dened for MATLAB, as there is no publicly
available grammar for the MATLAB language. The compiler accepts as input a MATLAB
script (from here on referred to as main program), that maycontain several M-le calls. The
lexical analyzer, which is generated by lex [LS], reads and converts the main program into a
stream of tokens that are processed by a syntax analyzer, which is generated by yacc [Joh],
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