# Intro12

Translating to and from a known language provides useful
beginning exercises in learning a new one. The following provides
examples.

Cover the right side of the page and make
a serious attempt to translate the sentences on the left
to English; that is, state succinctly in English what the verb
defined by each sentence does. Use any available aids,
including the dictionary and experimentation on the computer:

 f1=: <: Decrement (monad); Less or equal f2=: f1&9 Less or equal 9 f3=: f2 *. >:&2 Interval test 2 to 9 (inclusive) f4=: f3 *. <. = ] In 2 to 9 and integer f5=: f3 +. <. = ] In 2 to 9 or integer g1=: %&1.8 Divide by 1.8 g2=: g1^:_1 Multiply by 1.8 g3=: -&32 Subtract 32 g4=: g3^:_1 Add 32 g5=: g1@g3 Celsius from Fahrenheit g6=: g5^:_1 Fahrenheit from Celsius h1=: >./ Maximum over list (monad) h2=: h1-<./ Spread. Try h2 b with the parabola: b=:(-&2 * -&3) -:i.12 h3=: h1@]-i.@[*h2@]%<:@[ Grid. Try 10 h3 b h4=: h3 <:/ ] Barchart. Try 10 h4 b h5=: {&' *' @ h4 Barchart. Try 10 h5 b

After entering the foregoing definitions, enter each
verb name alone to display its definition, and learn to
interpret the resulting displays. To see several forms of display,
first enter 9!:3 (2 4 5) .

Cover the left side of the page,
and translate the English definitions on the right
back into J.

Exercises

12.1   These exercises are grouped by topic and organized
like the section, with programs that are first to be read