3.9 if

The if command allows commands to be executed conditionally.

Syntax:

      if (<condition>) <command-line> [; else if (<condition>) ...; else ...]

<condition> will be evaluated. If it is true (non-zero), then the command(s) of the <command-line> will be executed. If <condition> is false (zero), then the entire <command-line> is ignored until the next occurrence of ‘else‘. Note that use of ‘;‘ to allow multiple commands on the same line will _not_ end the conditionalized commands.

Examples:

      pi=3
      if (pi!=acos(-1)) print "?Fixing pi!"; pi=acos(-1); print pi

will display:

      ?Fixing pi!
      3.14159265358979

but

      if (1==2) print "Never see this"; print "Or this either"

will not display anything.

else:

      v=0
      v=v+1; if (v%2) print "2" ; else if (v%3) print "3"; else print "fred"

(repeat the last line repeatedly!)

See reread for an example of how if and reread can be used together to perform a loop.