SCL Fundamentals

SCL Constants

In SCL, a constant (or literal) is a fixed value that can be either a number or a character string. Constants can be used in many SCL statements, including assignment and IF-THEN statements. They can also be used as values for certain options.

Numeric Constants

A numeric constant is a number that appears in a SAS statement, and it can be presented in the following forms:

standard syntax, in which numeric constants are expressed as integers, can be specified with or without a plus or minus sign, and can include decimal places.
scientific (E) syntax, in which the number that precedes the E is multiplied by the power of ten indicated by the number that follows the E.
hexadecimal syntax, in which a numeric hex constant starts with a numeric digit (usually 0), can be followed by more hexadecimal digits, and ends with the letter X. The constant can contain up to 16 hexadecimal digits (0 to 9, A to F).
special SAS date and time values, in which the date or time is enclosed in single or double quotation marks, followed by a D (date), T (time), or DT (datetime) to indicate the type of value (for example, '15jan99'd).

Character Constants

A character constant can consist of 1 to 32,767 characters and must be enclosed in quotation marks. Character constants can be represented in the following forms:

hexadecimal form, in which a string of an even number of hex characters is enclosed in single or double quotation marks, followed immediately by an X, as in this example:
```
'534153'x
```
bit form, in which a string of 0s, 1s, and periods is surrounded by quotation marks and is immediately followed by a B. Zero tests whether a bit is off, 1 tests whether a bit is on, and a period ignores a bit. Commas and blanks can be inserted in the bit mask for readability without affecting its meaning.

In the following example, if the third bit of A (counting from the left) is on, and the fifth through eighth bits are off, then the comparison is true and the expression results in 1. Otherwise, the comparison is false and the expression results in 0.
```
if a='..1.0000'b then do;
```
Bit constants cannot be used as literals in assignment statements. For example, the following statement is not valid:
```
x='0101'b;   /* incorrect */
```

If a character constant includes a single quotation mark, then either write the quotation mark as two consecutive single quotation marks or surround the entire value with double quotation marks, as shown in the following examples:

possession='Your"s';
company="Your's and Mine"
company="Your""s and Mine"

To use a null character value as an argument to a function in SCL, either use '' (without a space) or use a blank value with ' ' (with a space).

Numeric-to-Character Conversion

If a value is inconsistent with the variable's data type, SCL attempts to convert the value to the expected type. SCL automatically converts character variables to numeric variables and numeric variables to character variables, according to the following rules:

A character variable is converted to numeric when the character variable is used
- with an operator that requires numeric operands (for example, the plus sign)
- with a comparison operator (for example, the equal sign) to compare a character variable and a numeric variable
- on the right side of an assignment statement, when a numeric variable is on the left side.
A numeric variable is converted to character when the numeric variable is used
- with an operator that requires a character value (for example, the concatenation operator)
- on the right side of an assignment statement, when a character variable is on the left side.

When a variable is converted automatically, a message in the LOG window warns you that the conversion took place. If a conversion from character to numeric produces invalid numeric values, then a missing value is assigned to the result, an error message appears in the LOG window, and the value of the automatic variable _ERROR_ is set to 1.

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