: SQUARE ( n -- n^2 ) DUP * ;
Ask the right questions to secure the right Forth talent among an increasingly shrinking pool of talent.
**Forth** is a stack-based computer programming language designed in the 1970s by Charles Moore. It is known for its simplicity, elegance, and efficiency. Forth is a compiled language, which means that it is translated into machine code before it is executed. This makes Forth very fast, but it also means that it is not as portable as interpreted languages like Python or Java. Forth is often used in embedded systems, where speed and efficiency are essential. **Sources:** * [Forth Wikipedia page](https://en.wikipedia.org/wiki/Forth_(programming_language)) * [Forth Language Reference Manual](https://www.forth.org/fortran/forthref.html)
The next 20 minutes of the interview should attempt to focus more specifically on the development questions used, and the level of depth and skill the engineer possesses.
'SWAP' command in Forth is used to swap the top two items on the stack. If the top two items are 3 and 4, after executing 'SWAP' the top item would be 3 and the second item would be 4.
'DUP' is used to duplicate the top item on the stack. For example, if the top item on the stack is 3, after executing 'DUP', the stack would have two 3's on top.
Immediate words in Forth are executed as soon as they are encountered during the compilation process, while non-immediate words are not executed until the program is run.
The two main types of words in Forth are defining words and executing words. Defining words are used to create new words and executing words perform a specific operation.
The stack in Forth is a LIFO (Last In, First Out) data structure that is used for temporary storage of data and return addresses.
The tech industry is always evolving. A good developer should stay updated with the latest advancements to ensure they are using the best and most efficient methods.
Software development is often a team effort. The candidate should be able to collaborate effectively with others, share ideas, and take constructive criticism.
Problem-solving is a crucial skill for developers. The candidate should be able to identify, troubleshoot, and fix issues in the code.
Since Forth is a stack-based language, having experience with this type of programming is crucial to effectively use the language.
The ability to write quality code is essential for any developer. It ensures that the code can be easily understood, maintained, and optimized by others.
A proficient Forth developer should have a strong understanding of the language, its syntax, and how to use it effectively.
The next 20 minutes of the interview should attempt to focus more specifically on the development questions used, and the level of depth and skill the engineer possesses.
'CREATE' is used to define a new word and 'DOES>' is used to give it a runtime behavior. For example, 'CREATE ARRAY 100 ALLOT DOES> @' creates a 100-element array and defines its behavior at runtime.
A loop in Forth can be implemented using the 'DO' and 'LOOP' commands. For example, '5 0 DO I . LOOP' will print the numbers 0 to 4.
'POSTPONE' and '[COMPILE]' are both used to compile a word at runtime. However, 'POSTPONE' works with both immediate and non-immediate words, while '[COMPILE]' only works with non-immediate words.
The 'DROP' command in Forth is used to remove the top item from the stack.
You can create a new defining word in Forth using the ':' command. For example, ': SQUARE DUP * ;' would define a new word called 'SQUARE' that squares a number.
A skilled Forth engineer should demonstrate deep knowledge of the Forth language, problem-solving capabilities, and strong debugging skills. Red flags would include inability to explain complex Forth concepts, lack of hands-on experience, and poor communication skills.
: SQUARE ( n -- n^2 ) DUP * ;
: GREETING ( -- ) 'Hello, World!' . ; GREETING
: ARRAY ( n1 n2 -- array ) CREATE CELLS ALLOT ; 2 3 ARRAY myArray
: PARALLEL ( xt1 xt2 -- ) 2DUP 2>R ['] THREAD >R EXECUTE R> EXECUTE ;
: CLASS ( -- ) CREATE DOES> @ ; : METHOD ( xt class -- ) >BODY ! ; 3 CLASS MyClass ' + MyClass METHOD
: FIB ( n -- n1 ) DUP 2 < IF DROP 1 ELSE DUP 1- RECURSE SWAP 2 - RECURSE + THEN ;
The final few interview questions for a Forth candidate should typically focus on a combination of technical skills, personal goals, growth potential, team dynamics, and company culture.
Multitasking in Forth can be achieved using the 'PAUSE' command which allows another task to run, and the 'RESUME' command which resumes a paused task. There is also a 'FORGET' command to remove a task.
Errors can be handled in Forth using the 'CATCH' and 'THROW' commands. 'CATCH' executes a word and returns an error code, while 'THROW' stops execution and returns the error code if it is not zero.
The 'SEE' command in Forth is used to decompile a word and display its definition.
'LEAVE' is used to prematurely end a 'DO' loop, while 'EXIT' is used to prematurely end a word definition.
Recursion can be implemented in Forth using the 'RECURSE' command. For example, ': FACTORIAL DUP 1 > IF DUP 1- RECURSE * THEN ;' defines a recursive factorial function.
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