**CIGAL Reference Manual, Chapter 2 (Commands): IF**
===== IF -- Conditional test within a CIGAL macro program =====
**usage: if(expression) command**\\
**or: if(expression) command**\\
**or: if(expression) {...many commands}**\\
**or: if(expression) {...many commands} else {...many commands}**\\

The IF statement is used to control the flow of command execution.
The "expression" argument to the IF command can be anything that evaluates
to a number.  If the number is not zero, then the IF tests true; if the
expression results in a zero value, then the test is false.  A TRUE result
means that the 'command' part of the IF statement is executed as the next
command; or if the brackets are used, then the whole block of commands
between the pair of brackets are executed.  The ELSE part of the command
is skipped if the result was TRUE.  If the result was FALSE, then the
first command or block of commands is skipped and only the commands in the
ELSE block, if present, are executed.

Any number of commands can be enclosed within a pair of brackets.  If
an end-of-file is encountered before the closing bracket, then an error is
reported.  IF statements can be nested in macro programs up to 20 blocks deep.

Spaces are optional within the test condition of an IF statement, but
there must be no spaces between the IF and the left parenthesis, '(', and
there must be a space after the last right parenthesis of the test
condition.

NOTE: When comparing character strings only an exact match will make '=='
true.  For '!=' to be true the two strings must differ at some character;
if one string is an abbreviation of the other, then '!=' will be false.
If you want to accept abbreviations, test if STRING1 %%<=%% STRING2.  An empty
string will always be != to a nonempty string.

Valid examples:
          if(a) ftype 'A= %d is nonzero\n' a
          if(accept('Enter yes or no',string) <= 'yes') return
          if(a > 2 & b < 100 | (a == 5 & b > 0)) {
                  c = 1
          } else {
                  type 'Values out of range'
                  if(c == 0) return
          }
          if(a > 2) return

Invalid examples:
          if (a > 2) return               ; space between IF and (
          if(a > 2)return                 ; no space between ) and RETURN

**See Also:**\\
[[jvs:cigal|CIGAL Home]], 
[[jvs:cigal:manual|CIGAL Manual]], 
[[jvs:cigal:manual:chapter2|Commands List]], 
[[jvs:cigal:manual:help|Manual Help]]