IRAF help page for package language, program if

• expression
• statement1, statement2

if (expression) statement1 [else statement2]

expression

statement1, statement2

The if statement is used to execute a statement only if the specified condition is true. An optional else clause may be given to execute a different statement if the condition is false.

1. Add X to Y only if X is less than Y.

	if (x < y)
	    y += x

2. If X is less than 10 print "small", else print "big".

	if (x < 10)
	    print ("small")
	else
	    print ("big")

3. The else if construct.

	if (str == "+")
	    val += x
	else if (str == "-")
	    val -= x
	else if
	    ...

4. Nesting, use of braces.

	if (i > 0) {
	    if (i < 10) {
		print ("0")
		sum = sum * 10 + i
	    } else
		print (" ")
	}

SEE ALSO, for, case, break, next,