Today we will help you to understand and resolve Error G0064: Operand Missing. We will answer the questions:

• What is an operand?
• How do common mathematical and non-mathematical operators interact with operands?
• What are common causes of operand missing errors?

What is an operand?

An operand is a symbol that an operator operates on. For example, in the line below:

X = 4 + 5;

The plus sign is the operator and both 4 and 5 are operands.

Mathematical and Logical Operators

When you think of operators, the mathematical and logical operators tend to come to mind first. For example, operators like those shown in the table below.

Operand Missing Errors with Mathematical and Logical Operators

Missing operand errors that occur with mathematical operators tend to be simple to understand and fix, so we will only show one example.

Example 1

// Multiply 6 by 5 
// and print  
// the result
6.*5;

// The left-hand 
// operand is 
// missing
.*5;

Non-mathematical Operators

Unlike the logical and mathematical operators, many of the “other” operators are not commonly noticed or considered.

Comma Operator Examples

Comma Operator Example One

// Create a 4x2 matrix with 
// random normally 
// distributed numbers
X = rndn(4,2);

// No operands on either 
// side of the comma 
// operator
X = rndn(,);

Comma Operator Example Two

// Assign the element from  
// the 6th row and first 
// column to Z
Z = X[6,1];

// The operand to the right 
// of the comma operator 
// is missing
Z = X[6, ];

Colon Operator Example

Operand missing statements with the colon operator will look like the previous comma operator errors.

// Assign the 3rd to 5th 
// elements from the vector
// y to u
u = y[3:5];

// The operand to the
// right of the colon 
// operator is missing
u = y[3: ];

Print Statements and the Space Operator

The usage of space operator is probably the most likely “operand missing” error to trip up new GAUSS users.

The print statement takes a space-separated list of items to print. For example:

print 4 5 6;

will return:

4.0000    5.0000    6.0000

Similarly, we can print the same data with variables like this:

A = 4;
B = 5;

print A B 6;

And GAUSS will again return:

4.0000    5.0000    6.0000

So far this is quite simple and something you may have done without a thought. However, adding an operator can cause a problem. For example, because the print statement uses the space operator to separate the items to print, the statement:

print A + B;

is interpreted by GAUSS as the following instructions:

Print the value of A.
Print the value of +.
Print the value of B.

Therefore, when GAUSS gets to the + sign, it does not see enough operands, because it has already been told to print A.

You can resolve this by removing the space operator between A, + and B, or by adding parentheses around the statement.

A = 4;
B = 5;

// Option 1: Add parentheses 
// around the sum of A and B
print (A + B);

// Option 2: Remove space operator 
// to print the sum of A and B
print A+B;

The parentheses (or dropped spaces) only need to be around the operator. The table below shows a few variations and the resulting printed output.

print (4 + 5) 6;

print (4 + 5)*6;

print  ((4 + 5) / 6);

print 4 5*6;

Conclusion

Congratulations! In today's blog, you have learned:

• What mathematical, logical, and non-mathematical operands are in GAUSS.
• Common causes of the G0064: Operand Missing error.

Further reading

1. Understanding Errors | G0025 : Undefined symbol
2. Understanding Errors: G0058 Index out-of-Range
3. GAUSS Basics 6: Logical and relational operators