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If n is greater than the length of the string then most implementations return the whole string (exceptions exist – see code examples). Note that for variable-length encodings such as UTF-8 , UTF-16 or Shift-JIS , it can be necessary to remove string positions at the end, in order to avoid invalid strings.
The Tcl programming language has a command called eval, which executes the source code provided as an argument. Tcl represents all source code as strings, with curly braces acting as quotation marks, so that the argument to eval can have the same formatting as any other source code.
Tcl supports multiple programming paradigms, including object-oriented, imperative, functional, and procedural styles. It is commonly used embedded into C applications, [11] for rapid prototyping, scripted applications, GUIs, and testing. [12] Tcl interpreters are available for many operating systems, allowing Tcl code to run on a wide variety ...
Non-interpolated strings may also escape sequences, in which case they are termed a raw string, though in other cases this is separate, yielding three classes of raw string, non-interpolated (but escaped) string, interpolated (and escaped) string. For example, in Unix shells, single-quoted strings are raw, while double-quoted strings are ...
Regular expressions can often be created ("induced" or "learned") based on a set of example strings. This is known as the induction of regular languages and is part of the general problem of grammar induction in computational learning theory.
Expect is an extension to the Tcl scripting language written by Don Libes. [2] The program automates interactions with programs that expose a text terminal interface. Expect, originally written in 1990 for the Unix platform, has since become available for Microsoft Windows and other systems.
Basically, object code for the language's interpreter needs to be linked into the executable. Source code fragments for the embedded language can then be passed to an evaluation function as strings. Application control languages can be implemented this way, if the source code is input by the user. Languages with small interpreters are preferred.
Both arguments are passed as strings (in Tcl everything within curly brackets is a string). In the above example the condition is not evaluated before calling the function. Instead, the implementation of the if function receives the condition as a string value and is responsible to evaluate this string as an expression in the callers scope. [7]