If you want to know:
- Is J open source / where is the source code for J? etc.
- What license is J under? Is J under the GPL? etc.
Then see: Source Code or License
If you want to know:
- Does J have lexical closure?
How do you solve Paul Graham's Accumulator Generator challenge in J?
Then see: Lexical Closure
Start compiling lists of possible FAQs here.
Please add your ideas for FAQs to answer here. Particularly "newbie FAQs" or pitfalls.
- FAQs for newbies
Why doesn't +:^:3 2 work?
$&> ,<'hello' is 5 but $>,<'hello is 1 5. Why?
Why doesn't (;: 'this is j')-:'this';'is';'j' hold? There's something of an answer at Parse, Lex, Execute
- General FAQs
Why does ''-:i.0 hold? Because no items differ.
What's up with 'boxed' -: datatype >0$a:? It's impossible to know the datatype of the contents boxes of that aren't there. Since boxed arrays can front any data type (and even multiple data types, i.e. when used to junction heterogeneous data), this answer is appropriate. What should be the result of datatype > 0 $ 'text';1bsome 1bnumbers;s:' symbols'?
The tedious arithmetic identity questions. Division by zero (ie 0=0%0 and _1=1%0) discussed in the paper by E. E. McDonnell, power (ie 1=0^0) discussed on the college math 0^0 thread on the Forums, and may be required if 0=0%0.
Explain execution of a verb on an empty frame e.&0@:$ with a cell of fills.