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Overview
Comment:Fixed some grammar and spelling in the th1.md doc.
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SHA3-256: 40787f50119aced6d5be4678edbc30cd9d4d1b0652cd488ae3c5e99c7bd7b48b
User & Date: wyoung 2018-09-04 11:59:24
Context
2018-09-04
12:10
Added more info on quoting rules in Tcl/TH1 to the th1.md doc check-in: 30e9ccd5 user: wyoung tags: trunk
11:59
Fixed some grammar and spelling in the th1.md doc. check-in: 40787f50 user: wyoung tags: trunk
2018-09-03
16:12
Do away with compiler warning about uninitialized variable. check-in: af39da6d user: andybradford tags: trunk
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Changes to www/th1.md.

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operations are accomplished by converting from string to numeric, performing
the computation, then converting the result back into a string.  (This might
seem inefficient, but it is faster than people imagine, and numeric
computations do not come up very often for the kinds of work that TH1 does,
so it has never been a factor.)

A TH1 script consist of a sequence of commands.
Each command is terminated by the first (unescaped) newline or ";" character.
The text of the command (excluding the newline or semicolon terminator)
is broken into space-separated tokens.  The first token is the command
name and subsequent tokens are the arguments.  In this since, TH1 syntax
is similar to the familiar command-line shell syntax.

A token is any sequence of characters other than whitespace and semicolons.
Or, all text without double-quotes is a single token even if it includes
whitespace and semicolons.  Or, all text without nested {...} pairs is a
single token.

The nested {...} form of tokens is important because it allows TH1 commands
to have an appearance similar to C/C++.  It is important to remember, though,
that a TH1 script is really just a list of text commands, not a context-free
language with a grammar like C/C++.  This can be confusing to long-time
C/C++ programmers because TH1 does look a lot like C/C++.  But the semantics
of TH1 are closer to FORTH or Lisp than they are to C.

Consider the "if" command in TH1.

        if {$current eq "dev"} {
          puts "hello"
        } else {
          puts "world"
        }

The example above is a single command.  The first token, and the name
of the command, is "if".
The second token is '$current eq "dev"' - an expression.  (The outer {...}
are removed from each token by the command parser.)  The third token
is the 'puts "hello"', with its whitespace and newlines.  The fourth token
is "else".  And the fifth and last token is 'puts "world"'.

The "if" command word by evaluating its first argument (the second token)
as an expression, and if that expression is true, evaluating its
second argument (the third token) as a TH1 script.
If the expression is false and the third argument is "else" then
the fourth argument is evaluated as a TH1 expression.

So, you see, even though the example above spans five lines, it is really
just a single command.

Summary of Core TH1 Commands
----------------------------







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operations are accomplished by converting from string to numeric, performing
the computation, then converting the result back into a string.  (This might
seem inefficient, but it is faster than people imagine, and numeric
computations do not come up very often for the kinds of work that TH1 does,
so it has never been a factor.)

A TH1 script consist of a sequence of commands.
Each command is terminated by the first *unescaped* newline or ";" character.
The text of the command (excluding the newline or semicolon terminator)
is broken into space-separated tokens.  The first token is the command
name and subsequent tokens are the arguments.  In this sense, TH1 syntax
is similar to the familiar command-line shell syntax.

A token is any sequence of characters other than whitespace and semicolons.
Or, all text without double-quotes is a single token even if it includes
whitespace and semicolons.  Or, all text without nested {...} pairs is a
single token.

The nested {...} form of tokens is important because it allows TH1 commands
to have an appearance similar to C/C++.  It is important to remember, though,
that a TH1 script is really just a list of text commands, not a context-free
language with a grammar like C/C++.  This can be confusing to long-time
C/C++ programmers because TH1 does look a lot like C/C++, but the semantics
of TH1 are closer to FORTH or Lisp than they are to C.

Consider the `if` command in TH1.

        if {$current eq "dev"} {
          puts "hello"
        } else {
          puts "world"
        }

The example above is a single command.  The first token, and the name
of the command, is `if`.
The second token is `$current eq "dev"` - an expression.  (The outer {...}
are removed from each token by the command parser.)  The third token
is the `puts "hello"`, with its whitespace and newlines.  The fourth token
is `else"`  And the fifth and last token is `puts "world"`.

The `if` command evaluates its first argument (the second token)
as an expression, and if that expression is true, evaluates its
second argument (the third token) as a TH1 script.
If the expression is false and the third argument is `else`, then
the fourth argument is evaluated as a TH1 expression.

So, you see, even though the example above spans five lines, it is really
just a single command.

Summary of Core TH1 Commands
----------------------------