TCL programming introduction (2)

TCL programming introduction (2)

List A string is interpreted as a list. A list is a result-like string that contains many fields separated by spaces. For example, "Al Sue Anne John" is an example table with four elements. line feed in the list is considered as a separator. For example: B c {d E {f g h} is a list of three elements: B, c, and {d E {f g h }}. TCL commands Concat, foreach, lappend, lindex, linsert, list, llength, lrange, lreplace, lsearch, and lsort allow you to operate on the list. Regular Expression TCL provides two commands for regular expressions: Regexp and regsub. Here, the regular expression is actually an extended regular expression, which is consistent with egrep. Supports ^ $. +? > <() | [] Command result Each Command has two results: an exit value and a string. The exit value indicates whether the command is correctly executed and the string provides additional information. Effective responses are formulated in 'tcl. H "as follows: Tcl_ OK The command is correctly executed, and the string gives the return value of the command. Tcl_error Indicates that an error occurs and the string provides an error description. The global variable errorinfo contains a human-readable error description and error message used by the global variable errorcode machine. Tcl_return The return command is called. The current command (usually a function) must be returned immediately. The string contains the returned value. Tcl_break Indicates that the break has been called, and the nearest loop must be immediately returned and jumped out. The string should be empty. Tcl_continue This indicates that the continue has been called and the nearest loop must be returned immediately without jumping out. The string should be empty. TCL programmers generally need to care about the exit value. The TCL interpreter immediately stops execution after an error is detected. Procedures Function TCL allows you to use the proc command to expand the command (to define a new command). After the definition, it can be used like other built-in commands. For example: Proc pf {STR }{ Puts $ Str } PF "Hello World" There is something that beginners don't pay attention to here. The above definition must be written like that. You cannot write it as follows: Proc pf {STR} { Puts $ Str }   Because proc is actually just a command and ends with a line break or a semicolon, it uses cluster Parameters to pass the function body. Proc is defined as follows: Proc name ARGs tclcommand Variables: scalars and Arrays   Variable: Scalar and vector (I .e. array) Vector is an array, while scalar is a variable without the following table. We use C for analogy: Int I; // I is a scalar Int J [10]; // J is a vector.   Variables do not need to be defined. They are automatically created when used. TCL supports two types Variable: Scalar and vector For example, Set I 100 Set J (0) 10 Set K (1, 3) 20   I is a scalar, and J is a vector. When referencing: $ I $ J (0) $ K (1, 3)