mumps syntax declaration

Q   ZR $ZTLP I Q=-1 S Q,A=F G T
I Q< S A=F G R

How to identify Label, Keyword and Variable in MUMPS?

What is Q in above code? i.e. Label, Variable or Key word?

What are the rules to define variable keyword and subroutine?

Otherwise it is difficult to identify could you开发者_Go百科 suggest why because I can't understand my existing code which is what?

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Q means QUIT in first instance but then I Q=-1 is IF Q EQUALS -1 - Q is a variable here too - not very good practice

S Q,A=F  again SET Q and A = F

I Q< S A=F G R  if Q is less than null (???) SET A=F  then GOTO line R.

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The secret is: whitespaces.

General MUMPS program line syntax is: ...

Lebel and arguments are optional: when a line has no label, it begins with tab, when a command has no arguments (it happens in rare cases, e.g.: Quit), the command is followed by two spaces.

When a line begins with command (no label and no tab), it's not part of a program, but it is an immediatelly executed command.

You may feel that it's confusing, but remember, MUMPS was designed when machines were slow; it's easy to parse commands if they are strictly delimited. That's why commands can be abbreviated as single-letter, and also that's why MUMPS have no operation precedence (newer MUMPS systems are configurable to use operator precedence instead of traditional left-to-right processing order).